Add video preview, source crop, find-videos, and render toasts

Bring the Video tab closer to Shorts with 4K preview stills and crop
modes (none, auto, center, plus the visual editor). Settings store a
default source folder so Find videos can collect output.avi sequences.
Cap the FFmpeg log with auto-scroll, hide repeat spam, and show a
Windows notification when a video or short finishes or fails.

AmiReel.Tests/Models/AppSettingsTests.cs

@@ -81,6 +81,55 @@ public class AppSettingsTests
         Assert.AreEqual("3", normalized.FadeSeconds);
         Assert.AreEqual("4", normalized.EndCardHoldSeconds);
         Assert.AreEqual("10", normalized.ThumbnailInterval);
+        Assert.AreEqual("", normalized.SourceSearchFolder);
+        Assert.AreEqual("Auto", normalized.VideoSourceCropMode);
+        Assert.AreEqual("0", normalized.VideoCropLeft);
+    }
+
+    [TestMethod]
+    public void Normalize_WithBlankVideoSourceSettings_RestoresDefaults()
+    {
+        // Arrange
+        AppSettings settings = AppSettings.Default(@"C:\Videos") with
+        {
+            SourceSearchFolder = null!,
+            VideoSourceCropMode = "",
+            VideoCropLeft = "  ",
+            VideoCropRight = "",
+            VideoCropTop = "",
+            VideoCropBottom = "",
+        };
+
+        // Act
+        AppSettings normalized = settings.Normalize(@"C:\Videos");
+
+        // Assert
+        Assert.AreEqual("", normalized.SourceSearchFolder);
+        Assert.AreEqual("Auto", normalized.VideoSourceCropMode);
+        Assert.AreEqual("0", normalized.VideoCropLeft);
+        Assert.AreEqual("0", normalized.VideoCropRight);
+        Assert.AreEqual("0", normalized.VideoCropTop);
+        Assert.AreEqual("0", normalized.VideoCropBottom);
+    }
+
+    [TestMethod]
+    public void Normalize_WithSourceSearchFolder_KeepsItUnchanged()
+    {
+        // Arrange
+        AppSettings settings = AppSettings.Default(@"C:\Videos") with
+        {
+            SourceSearchFolder = @"D:\AmigaIntrosVideos",
+            VideoSourceCropMode = "Center",
+            VideoCropLeft = "12",
+        };
+
+        // Act
+        AppSettings normalized = settings.Normalize(@"C:\Videos");
+
+        // Assert
+        Assert.AreEqual(@"D:\AmigaIntrosVideos", normalized.SourceSearchFolder);
+        Assert.AreEqual("Center", normalized.VideoSourceCropMode);
+        Assert.AreEqual("12", normalized.VideoCropLeft);
     }
 
     [TestMethod]

AmiReel.Tests/Services/FfmpegOutputFilterTests.cs

@@ -16,6 +16,8 @@ public class FfmpegOutputFilterTests
     [DataRow("Stream #0:0: Video: mjpeg")]
     [DataRow("Duration: 00:01:00.00, start: 0.000000, bitrate: 128 kb/s")]
     [DataRow("video:1024kB audio:128kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.5%")]
+    [DataRow("Last message repeated 1 times")]
+    [DataRow("Last message repeated 24 times")]
     public void IsBoilerplateLine_WithKnownFfmpegBanner_ReturnsTrue(string line)
     {
         // Act

AmiReel.Tests/Services/ProcessRunnerTests.cs

@@ -0,0 +1,34 @@
+using AmiReel.Services;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace AmiReel.Tests.Services;
+
+[TestClass]
+public class ProcessRunnerTests
+{
+    [TestMethod]
+    public void IsNoise_WithLastMessageRepeated_ReturnsTrue()
+    {
+        // Arrange
+        FfmpegOutputLine line = FfmpegProgressParser.Parse("Last message repeated 1 times");
+
+        // Act
+        bool result = ProcessRunner.IsNoise(line);
+
+        // Assert
+        Assert.IsTrue(result);
+    }
+
+    [TestMethod]
+    public void IsNoise_WithCropdetectSpec_ReturnsFalse()
+    {
+        // Arrange
+        FfmpegOutputLine line = FfmpegProgressParser.Parse("crop=672:ih:56:0");
+
+        // Act
+        bool result = ProcessRunner.IsNoise(line);
+
+        // Assert
+        Assert.IsFalse(result);
+    }
+}

AmiReel.Tests/Services/RenderNotifierTests.cs

@@ -0,0 +1,67 @@
+using AmiReel.Services;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace AmiReel.Tests.Services;
+
+[TestClass]
+public class RenderNotifierTests
+{
+    [TestMethod]
+    public void DescribeCompleted_ForVideo_UsesRenderCompleteCopy()
+    {
+        // Act
+        (string title, string body) = RenderNotifier.DescribeCompleted(shorts: false);
+
+        // Assert
+        Assert.AreEqual("Render complete", title);
+        StringAssert.Contains(body, "successfully");
+    }
+
+    [TestMethod]
+    public void DescribeCompleted_ForShorts_UsesShortCompleteCopy()
+    {
+        // Act
+        (string title, string body) = RenderNotifier.DescribeCompleted(shorts: true);
+
+        // Assert
+        Assert.AreEqual("Short complete", title);
+        StringAssert.Contains(body, "Short");
+    }
+
+    [TestMethod]
+    public void DescribeFailed_WithBlankSummary_UsesFallbackBody()
+    {
+        // Act
+        (string title, string body) = RenderNotifier.DescribeFailed("   ");
+
+        // Assert
+        Assert.AreEqual("Render failed", title);
+        Assert.AreEqual("The render failed.", body);
+    }
+
+    [TestMethod]
+    public void DescribeFailed_WithLongSummary_TruncatesBody()
+    {
+        // Arrange
+        string summary = new('x', 250);
+
+        // Act
+        (string title, string body) = RenderNotifier.DescribeFailed(summary);
+
+        // Assert
+        Assert.AreEqual("Render failed", title);
+        Assert.AreEqual(180, body.Length);
+        StringAssert.EndsWith(body, "...");
+    }
+
+    [TestMethod]
+    public void DescribeCancelled_ReturnsCancelledCopy()
+    {
+        // Act
+        (string title, string body) = RenderNotifier.DescribeCancelled();
+
+        // Assert
+        Assert.AreEqual("Render cancelled", title);
+        StringAssert.Contains(body, "cancelled");
+    }
+}

AmiReel.Tests/Services/RenderPipelineTests.cs

@@ -127,6 +127,154 @@ public class RenderPipelineTests
         RenderPipeline.Validate(settings);
     }
 
+    [TestMethod]
+    public void ValidatePreview_WithMissingOutputName_DoesNotThrow()
+    {
+        // Arrange
+        string directory = CreateTempDirectory();
+        string input = Path.Combine(directory, "clip.avi");
+        File.WriteAllText(input, "data");
+        RenderSettings settings = ValidSettings([input], "") with { OutputName = "" };
+
+        // Act & Assert (no exception)
+        RenderPipeline.ValidatePreview(settings);
+    }
+
+    [TestMethod]
+    public void ValidatePreview_WithNoInputFiles_ThrowsArgumentException()
+    {
+        // Arrange
+        RenderSettings settings = ValidSettings([], @"C:\out");
+
+        // Act & Assert
+        Assert.ThrowsExactly<ArgumentException>(() => RenderPipeline.ValidatePreview(settings));
+    }
+
+    [TestMethod]
+    public void BuildJoinVideoFilter_IncludesCropThenScaleAndPad()
+    {
+        // Arrange
+        RenderSettings settings = ValidSettings(["clip.avi"], @"C:\out");
+
+        // Act
+        string filter = RenderPipeline.BuildJoinVideoFilter(settings, "crop=iw-10-10:ih-4-4:10:4");
+
+        // Assert
+        StringAssert.StartsWith(filter, "crop=iw-10-10:ih-4-4:10:4,scale=2880:2160");
+        StringAssert.Contains(filter, "pad=3840:2160");
+    }
+
+    [TestMethod]
+    public void BuildSourceCropFilter_WithManualInsets_UsesEdgeCrop()
+    {
+        // Arrange
+        RenderSettings settings = ValidSettings(["clip.avi"], @"C:\out") with
+        {
+            CropLeft = 20,
+            CropRight = 10,
+            CropTop = 4,
+            CropBottom = 6,
+        };
+
+        // Act
+        string filter = RenderPipeline.BuildSourceCropFilter(settings, "crop=800:ih:40:0");
+
+        // Assert
+        Assert.AreEqual("crop=iw-20-10:ih-4-6:20:4", filter);
+    }
+
+    [TestMethod]
+    public void BuildSourceCropFilter_WithAutoDetection_UsesDetectedFilter()
+    {
+        // Arrange
+        RenderSettings settings = ValidSettings(["clip.avi"], @"C:\out") with
+        {
+            SourceCropMode = ShortSourceCropMode.Auto,
+        };
+
+        // Act
+        string filter = RenderPipeline.BuildSourceCropFilter(settings, "crop=800:ih:40:0");
+
+        // Assert
+        Assert.AreEqual("crop=800:ih:40:0", filter);
+    }
+
+    [TestMethod]
+    public void BuildSourceCropFilter_WithCenterMode_UsesFourByThreeCrop()
+    {
+        // Arrange
+        RenderSettings settings = ValidSettings(["clip.avi"], @"C:\out") with
+        {
+            SourceCropMode = ShortSourceCropMode.Center,
+        };
+
+        // Act
+        string filter = RenderPipeline.BuildSourceCropFilter(settings, "crop=800:ih:40:0");
+
+        // Assert
+        Assert.AreEqual(ShortsPipeline.DefaultSourceCropFilter, filter);
+    }
+
+    [TestMethod]
+    public void BuildSourceCropFilter_WithNoneMode_AppliesNoCrop()
+    {
+        // Arrange
+        RenderSettings settings = ValidSettings(["clip.avi"], @"C:\out") with
+        {
+            SourceCropMode = ShortSourceCropMode.None,
+        };
+
+        // Act
+        string filter = RenderPipeline.BuildSourceCropFilter(settings, "crop=800:ih:40:0");
+
+        // Assert
+        Assert.AreEqual("", filter);
+    }
+
+    [TestMethod]
+    public void BuildJoinVideoFilter_WithNoCrop_StartsAtScale()
+    {
+        // Arrange
+        RenderSettings settings = ValidSettings(["clip.avi"], @"C:\out");
+
+        // Act
+        string filter = RenderPipeline.BuildJoinVideoFilter(settings, "");
+
+        // Assert
+        StringAssert.StartsWith(filter, "scale=2880:2160");
+        Assert.IsFalse(filter.Contains("crop=", StringComparison.Ordinal));
+    }
+
+    [TestMethod]
+    public void PreviewSeekSeconds_WithDurationAfterTrim_StaysInsideRemainingClip()
+    {
+        // Act
+        double seek = RenderPipeline.PreviewSeekSeconds(4, 30);
+
+        // Assert
+        Assert.AreEqual(5.2, seek, 0.001);
+    }
+
+    [TestMethod]
+    public void PreviewSeekSeconds_WhenTrimIsPastDuration_ReturnsTrimStart()
+    {
+        // Act
+        double seek = RenderPipeline.PreviewSeekSeconds(40, 10);
+
+        // Assert
+        Assert.AreEqual(40, seek, 0.001);
+    }
+
+    [TestMethod]
+    public void FormatTimestamp_FormatsInvariantHoursMinutesSeconds()
+    {
+        // Act
+        string stamp = RenderPipeline.FormatTimestamp(4.414);
+
+        // Assert
+        Assert.AreEqual("00:00:04.414", stamp);
+    }
+
     [TestMethod]
     public void BuildProgressMessage_WithOnlyTime_ReturnsTimeRangeOnly()
     {

AmiReel.Tests/Services/ShortsPipelineTests.cs

@@ -380,6 +380,53 @@ public class ShortsPipelineTests
         Assert.AreEqual("crop=iw-120-80:ih-10-20:120:10", filter);
     }
 
+    [TestMethod]
+    public void SourceCropFiltersResolve_WithManualInsets_IgnoresAutoDetection()
+    {
+        // Act
+        string filter = SourceCropFilters.Resolve(ShortSourceCropMode.Auto, 8, 4, 2, 1, "crop=800:ih:40:0");
+
+        // Assert
+        Assert.AreEqual("crop=iw-8-4:ih-2-1:8:2", filter);
+    }
+
+    [TestMethod]
+    public void SourceCropFiltersResolve_WithNoneMode_ReturnsEmptyFilter()
+    {
+        // Act
+        string filter = SourceCropFilters.Resolve(ShortSourceCropMode.None, 0, 0, 0, 0, "crop=800:ih:40:0");
+
+        // Assert
+        Assert.AreEqual("", filter);
+    }
+
+    [TestMethod]
+    public void BuildVideoBaseFilter_WithNoCrop_ScalesTheFullSource()
+    {
+        // Act
+        string filter = ShortsPipeline.BuildVideoBaseFilter("", "scale=1000:-2:flags=lanczos", blur: 0, opacity: 1);
+
+        // Assert
+        StringAssert.Contains(filter, "[0:v]scale=1000:-2:flags=lanczos,setsar=1[fg]");
+        Assert.IsFalse(filter.Contains("[0:v]crop=", StringComparison.Ordinal));
+    }
+
+    [TestMethod]
+    public void TryBuildAutoHorizontalFilter_UsesMostCommonSpecAndEvenInset()
+    {
+        // Arrange
+        const string output =
+            "crop=800:480:100:0\n" +
+            "crop=800:480:100:0\n" +
+            "crop=760:480:140:0";
+
+        // Act
+        string? filter = SourceCropFilters.TryBuildAutoHorizontalFilter(output);
+
+        // Assert
+        Assert.AreEqual("crop=792:ih:104:0", filter);
+    }
+
     [TestMethod]
     public void SourceTargetWidth_SubtractsBothMargins()
     {

AmiReel.Tests/Services/SourceRecordingFinderTests.cs

@@ -0,0 +1,99 @@
+using AmiReel.Services;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace AmiReel.Tests.Services;
+
+[TestClass]
+public class SourceRecordingFinderTests
+{
+    private readonly List<string> _tempDirectories = [];
+
+    [TestCleanup]
+    public void Cleanup()
+    {
+        foreach (string directory in _tempDirectories)
+        {
+            try { Directory.Delete(directory, true); } catch { }
+        }
+    }
+
+    private string CreateTempDirectory()
+    {
+        string directory = Path.Combine(Path.GetTempPath(), "AmiReelTests", Guid.NewGuid().ToString("N"));
+        Directory.CreateDirectory(directory);
+        _tempDirectories.Add(directory);
+        return directory;
+    }
+
+    [TestMethod]
+    public void FindSequentialOutputs_WithMissingFolder_ReturnsEmpty()
+    {
+        // Act
+        IReadOnlyList<string> result = SourceRecordingFinder.FindSequentialOutputs(
+            Path.Combine(Path.GetTempPath(), "AmiReelTests", "missing-" + Guid.NewGuid().ToString("N")));
+
+        // Assert
+        Assert.AreEqual(0, result.Count);
+    }
+
+    [TestMethod]
+    public void FindSequentialOutputs_WithBlankFolder_ReturnsEmpty()
+    {
+        // Act
+        IReadOnlyList<string> result = SourceRecordingFinder.FindSequentialOutputs("   ");
+
+        // Assert
+        Assert.AreEqual(0, result.Count);
+    }
+
+    [TestMethod]
+    public void FindSequentialOutputs_WithOnlyOutputAvi_ReturnsSingleFile()
+    {
+        // Arrange
+        string directory = CreateTempDirectory();
+        string first = Path.Combine(directory, "output.avi");
+        File.WriteAllText(first, "one");
+
+        // Act
+        IReadOnlyList<string> result = SourceRecordingFinder.FindSequentialOutputs(directory);
+
+        // Assert
+        Assert.AreEqual(1, result.Count);
+        Assert.AreEqual(first, result[0]);
+    }
+
+    [TestMethod]
+    public void FindSequentialOutputs_WithNumberedSequence_ReturnsFilesUntilFirstGap()
+    {
+        // Arrange
+        string directory = CreateTempDirectory();
+        File.WriteAllText(Path.Combine(directory, "output.avi"), "0");
+        File.WriteAllText(Path.Combine(directory, "output_1.avi"), "1");
+        File.WriteAllText(Path.Combine(directory, "output_2.avi"), "2");
+        File.WriteAllText(Path.Combine(directory, "output_4.avi"), "skipped");
+        File.WriteAllText(Path.Combine(directory, "output.mp4"), "wrong-ext");
+
+        // Act
+        IReadOnlyList<string> result = SourceRecordingFinder.FindSequentialOutputs(directory);
+
+        // Assert
+        Assert.AreEqual(3, result.Count);
+        Assert.AreEqual("output.avi", Path.GetFileName(result[0]));
+        Assert.AreEqual("output_1.avi", Path.GetFileName(result[1]));
+        Assert.AreEqual("output_2.avi", Path.GetFileName(result[2]));
+    }
+
+    [TestMethod]
+    public void FindSequentialOutputs_WithoutBaseOutputAvi_ReturnsEmptyEvenIfNumberedExists()
+    {
+        // Arrange
+        string directory = CreateTempDirectory();
+        File.WriteAllText(Path.Combine(directory, "output_1.avi"), "1");
+
+        // Act
+        IReadOnlyList<string> result = SourceRecordingFinder.FindSequentialOutputs(directory);
+
+        // Assert
+        Assert.AreEqual(0, result.Count);
+    }
+}

App.xaml.cs

@@ -1,4 +1,5 @@
-using Microsoft.UI.Xaml;
+using AmiReel.Services;
+using Microsoft.UI.Xaml;
 using WinRT.Interop;
 
 namespace AmiReel;
@@ -29,6 +30,7 @@ public partial class App : Application
     {
         _window = new MainWindow();
         MainWindowHandle = WindowNative.GetWindowHandle(_window);
+        RenderNotifier.Register();
         _window.Activate();
     }
 }

MainPage.xaml

@@ -34,14 +34,22 @@
             <Grid.ColumnDefinitions>
                 <ColumnDefinition Width="*" />
                 <ColumnDefinition Width="*" />
+                <ColumnDefinition Width="Auto" />
             </Grid.ColumnDefinitions>
 
             <Border Grid.Column="0" Padding="18" Style="{StaticResource CardBorderStyle}">
                 <StackPanel Spacing="12">
                     <TextBlock Text="Source recordings" Style="{StaticResource SectionTitleStyle}" />
                     <StackPanel Orientation="Horizontal" Spacing="10">
-                        <Button Content="Add video files..." Click="AddInputs_Click" />
+                        <Button Content="Add video files..." Click="AddInputs_Click"
-                        <Button Content="Clear" Click="ClearInputs_Click" />
+                                AutomationProperties.Name="Add video files" />
+                        <Button x:Name="FindVideosButton"
+                                Content="Find videos"
+                                Click="FindVideos_Click"
+                                AutomationProperties.Name="Find videos in the default source folder"
+                                AutomationProperties.AutomationId="FindVideosButton" />
+                        <Button Content="Clear" Click="ClearInputs_Click"
+                                AutomationProperties.Name="Clear source recordings" />
                     </StackPanel>
                     <ListView x:Name="InputList"
                               Height="130"
@@ -50,12 +58,47 @@
                               AllowDrop="True"
                               DragOver="InputList_DragOver"
                               Drop="InputList_Drop"
+                              AutomationProperties.Name="Source recordings"
                               ToolTipService.ToolTip="Drag and drop video files here to add them" />
                     <Button x:Name="PreviewSourceButton"
                             Content="Preview selected"
                             Click="PreviewSource_Click"
                             HorizontalAlignment="Left"
-                            IsEnabled="False" />
+                            IsEnabled="False"
+                            AutomationProperties.Name="Preview selected source" />
+
+                    <TextBlock Text="Source crop" Style="{StaticResource SectionTitleStyle}" />
+                    <ComboBox x:Name="VideoCropModeBox" Header="Source crop" HorizontalAlignment="Stretch"
+                              AutomationProperties.Name="Source crop mode"
+                              AutomationProperties.AutomationId="VideoCropModeBox">
+                        <ComboBoxItem Content="None (keep full frame)" Tag="None" />
+                        <ComboBoxItem Content="Auto (remove left/right black borders)" Tag="Auto" />
+                        <ComboBoxItem Content="Center 4:3" Tag="Center" />
+                    </ComboBox>
+                    <TextBlock Text="Manual crop overrides the mode above. Leave at 0 to use the mode, or drag the kept region on a source frame."
+                               Style="{StaticResource MutedTextStyle}" TextWrapping="WrapWholeWords" />
+                    <Grid ColumnSpacing="10">
+                        <Grid.ColumnDefinitions>
+                            <ColumnDefinition Width="*" />
+                            <ColumnDefinition Width="*" />
+                            <ColumnDefinition Width="*" />
+                            <ColumnDefinition Width="*" />
+                        </Grid.ColumnDefinitions>
+                        <TextBox x:Name="VideoCropLeftBox" Grid.Column="0" Header="Crop left" Text="0"
+                                 AutomationProperties.Name="Crop left pixels" />
+                        <TextBox x:Name="VideoCropRightBox" Grid.Column="1" Header="Crop right" Text="0"
+                                 AutomationProperties.Name="Crop right pixels" />
+                        <TextBox x:Name="VideoCropTopBox" Grid.Column="2" Header="Crop top" Text="0"
+                                 AutomationProperties.Name="Crop top pixels" />
+                        <TextBox x:Name="VideoCropBottomBox" Grid.Column="3" Header="Crop bottom" Text="0"
+                                 AutomationProperties.Name="Crop bottom pixels" />
+                    </Grid>
+                    <Button x:Name="OpenVideoCropEditorButton"
+                            Content="Crop visually..."
+                            Click="OpenVideoCropEditor_Click"
+                            HorizontalAlignment="Left"
+                            AutomationProperties.Name="Open visual crop editor"
+                            AutomationProperties.AutomationId="OpenVideoCropEditorButton" />
                 </StackPanel>
             </Border>
 
@@ -75,16 +118,64 @@
                             <RowDefinition Height="Auto" />
                         </Grid.RowDefinitions>
 
-                        <TextBox x:Name="EndCardBox" Grid.Row="0" MinHeight="40" />
+                        <TextBox x:Name="EndCardBox" Grid.Row="0" MinHeight="40" Header="End card"
-                        <Button Grid.Row="0" Grid.Column="1" Content="Browse..." Click="BrowseEndCard_Click" VerticalAlignment="Stretch" MinWidth="120" />
+                                 AutomationProperties.Name="End card image" />
+                        <Button Grid.Row="0" Grid.Column="1" Content="Browse..." Click="BrowseEndCard_Click" VerticalAlignment="Bottom" MinWidth="120"
+                                AutomationProperties.Name="Browse end card" />
 
-                        <TextBox x:Name="OutputFolderBox" Grid.Row="1" MinHeight="40" />
+                        <TextBox x:Name="OutputFolderBox" Grid.Row="1" MinHeight="40" Header="Output folder"
-                        <Button Grid.Row="1" Grid.Column="1" Content="Browse..." Click="BrowseOutput_Click" VerticalAlignment="Stretch" MinWidth="120" />
+                                 AutomationProperties.Name="Output folder" />
+                        <Button Grid.Row="1" Grid.Column="1" Content="Browse..." Click="BrowseOutput_Click" VerticalAlignment="Bottom" MinWidth="120"
+                                AutomationProperties.Name="Browse output folder" />
 
-                        <TextBox x:Name="OutputNameBox" Grid.Row="2" Grid.ColumnSpan="2" MinHeight="40" />
+                        <TextBox x:Name="OutputNameBox" Grid.Row="2" Grid.ColumnSpan="2" MinHeight="40" Header="Output name"
+                                 AutomationProperties.Name="Output name" />
                     </Grid>
                 </StackPanel>
             </Border>
+
+            <StackPanel Grid.Column="2" Width="320" Spacing="10">
+                <TextBlock Text="Preview" Style="{StaticResource SectionTitleStyle}" />
+                <TextBlock x:Name="VideoPreviewStatusText"
+                           Text="Add source recordings, then update the preview to see the 4K look."
+                           Style="{StaticResource MutedTextStyle}"
+                           TextWrapping="WrapWholeWords" />
+                <Button x:Name="UpdateVideoPreviewButton"
+                        Content="Update preview"
+                        Click="UpdateVideoPreview_Click"
+                        HorizontalAlignment="Stretch"
+                        AutomationProperties.Name="Update video preview"
+                        AutomationProperties.AutomationId="UpdateVideoPreviewButton" />
+                <ProgressBar x:Name="VideoPreviewProgress"
+                             IsIndeterminate="True"
+                             Height="6"
+                             Visibility="Collapsed"
+                             AutomationProperties.Name="Video preview progress" />
+                <StackPanel Spacing="6">
+                    <TextBlock Text="Opening" Style="{StaticResource MutedTextStyle}" />
+                    <Border Width="292" Height="164"
+                            Background="{ThemeResource PageBrush}"
+                            BorderBrush="{ThemeResource BorderBrush}"
+                            BorderThickness="1"
+                            CornerRadius="8">
+                        <Image x:Name="VideoPreviewOpeningImage"
+                               Stretch="Uniform"
+                               AutomationProperties.Name="Opening frame preview" />
+                    </Border>
+                </StackPanel>
+                <StackPanel Spacing="6">
+                    <TextBlock Text="Closing" Style="{StaticResource MutedTextStyle}" />
+                    <Border Width="292" Height="164"
+                            Background="{ThemeResource PageBrush}"
+                            BorderBrush="{ThemeResource BorderBrush}"
+                            BorderThickness="1"
+                            CornerRadius="8">
+                        <Image x:Name="VideoPreviewClosingImage"
+                               Stretch="Uniform"
+                               AutomationProperties.Name="End-card preview" />
+                    </Border>
+                </StackPanel>
+            </StackPanel>
         </Grid>
 
         <Border Grid.Row="1" Padding="18" Style="{StaticResource CardBorderStyle}" x:Name="ShortsContentPanel" Visibility="Collapsed">
@@ -210,10 +301,11 @@
                         </Grid>
                         <ComboBox x:Name="ShortCropModeBox" Header="Source crop" HorizontalAlignment="Stretch"
                                   AutomationProperties.Name="Source crop mode">
+                            <ComboBoxItem Content="None (keep full frame)" Tag="None" />
                             <ComboBoxItem Content="Auto (remove left/right black borders)" Tag="Auto" />
                             <ComboBoxItem Content="Center 4:3" Tag="Center" />
                         </ComboBox>
-                        <TextBlock Text="Manual crop overrides auto/center. Leave at 0 to use the mode above, or drag the kept region on a source frame."
+                        <TextBlock Text="Manual crop overrides the mode above. Leave at 0 to use the mode, or drag the kept region on a source frame."
                                    Style="{StaticResource MutedTextStyle}" TextWrapping="WrapWholeWords" />
                         <Grid ColumnSpacing="10">
                             <Grid.ColumnDefinitions>
@@ -382,7 +474,10 @@
                          FontFamily="Consolas"
                          FontSize="12"
                          VerticalAlignment="Stretch"
-                         MinHeight="320" />
+                         MinHeight="160"
+                         MaxHeight="280"
+                         AutomationProperties.Name="FFmpeg log text"
+                         AutomationProperties.AutomationId="FfmpegLogBox" />
             </StackPanel>
         </Border>
 
@@ -497,6 +592,25 @@
                             <TextBlock Text="After a successful render, original recordings are moved into an originals subfolder of the output folder. Uncheck to leave them where they are."
                                        TextWrapping="WrapWholeWords"
                                        Style="{StaticResource MutedTextStyle}" />
+                            <Grid ColumnSpacing="10">
+                                <Grid.ColumnDefinitions>
+                                    <ColumnDefinition Width="*" />
+                                    <ColumnDefinition Width="Auto" />
+                                </Grid.ColumnDefinitions>
+                                <TextBox x:Name="SourceSearchFolderBox"
+                                         Grid.Column="0"
+                                         Header="Default source folder"
+                                         AutomationProperties.Name="Default folder for source recordings"
+                                         AutomationProperties.AutomationId="SourceSearchFolderBox" />
+                                <Button Grid.Column="1"
+                                        Content="Browse..."
+                                        Click="BrowseSourceSearchFolder_Click"
+                                        VerticalAlignment="Bottom"
+                                        AutomationProperties.Name="Browse default source folder" />
+                            </Grid>
+                            <TextBlock Text="Find videos on the Video tab looks here for output.avi, then output_1.avi, output_2.avi, and so on until a name is missing."
+                                       TextWrapping="WrapWholeWords"
+                                       Style="{StaticResource MutedTextStyle}" />
                         </StackPanel>
                     </Border>
 

MainPage.xaml.cs

@@ -7,6 +7,7 @@ using AmiReel.Models;
 using AmiReel.Services;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
+using Microsoft.UI.Xaml.Media;
 using Microsoft.UI.Xaml.Media.Imaging;
 using Windows.ApplicationModel.DataTransfer;
 using Windows.Storage;
@@ -31,6 +32,7 @@ public sealed partial class MainPage : Page
     private int _wizardIndex;
     private int _previewGeneration;
     private string? _previewDirectory;
+    private string? _videoPreviewDirectory;
 
     public MainPage()
     {
@@ -51,6 +53,12 @@ public sealed partial class MainPage : Page
         SelectTheme(_loadedSettings.Theme);
         ApplyTheme(_loadedSettings.Theme);
         MoveSourcesBox.IsChecked = _loadedSettings.ShouldMoveSourcesToOriginals;
+        SourceSearchFolderBox.Text = _loadedSettings.SourceSearchFolder;
+        VideoCropLeftBox.Text = _loadedSettings.VideoCropLeft;
+        VideoCropRightBox.Text = _loadedSettings.VideoCropRight;
+        VideoCropTopBox.Text = _loadedSettings.VideoCropTop;
+        VideoCropBottomBox.Text = _loadedSettings.VideoCropBottom;
+        SelectComboTag(VideoCropModeBox, _loadedSettings.VideoSourceCropMode);
 
         ShortHookBox.Text = _loadedSettings.ShortsHook;
         ShortWebsiteBox.Text = _loadedSettings.ShortsWebsite;
@@ -227,6 +235,48 @@ public sealed partial class MainPage : Page
 
     private void ClearInputs_Click(object sender, RoutedEventArgs e) => _inputs.Clear();
 
+    private async void FindVideos_Click(object sender, RoutedEventArgs e)
+    {
+        string folder = SourceSearchFolderBox.Text.Trim();
+        if (string.IsNullOrWhiteSpace(folder))
+        {
+            await ShowMessageAsync("Find videos", "Set a default source folder in Settings first.");
+            return;
+        }
+
+        if (!Directory.Exists(folder))
+        {
+            await ShowMessageAsync("Find videos", "The default source folder was not found.");
+            return;
+        }
+
+        IReadOnlyList<string> found = SourceRecordingFinder.FindSequentialOutputs(folder);
+        if (found.Count == 0)
+        {
+            await ShowMessageAsync("Find videos", "No output.avi sequence was found in the default source folder.");
+            return;
+        }
+
+        int added = 0;
+        foreach (string path in found)
+        {
+            if (_inputs.Contains(path, StringComparer.OrdinalIgnoreCase))
+                continue;
+
+            _inputs.Add(path);
+            added++;
+        }
+
+        if (added == 0)
+        {
+            await ShowMessageAsync("Find videos", "Those recordings are already in the source list.");
+            return;
+        }
+
+        if (InputList.SelectedItem is null && _inputs.Count > 0)
+            InputList.SelectedIndex = 0;
+    }
+
     private void InputList_DragOver(object sender, DragEventArgs e)
     {
         e.AcceptedOperation = e.DataView.Contains(StandardDataFormats.StorageItems)
@@ -275,6 +325,14 @@ public sealed partial class MainPage : Page
             OutputFolderBox.Text = folder.Path;
     }
 
+    private async void BrowseSourceSearchFolder_Click(object sender, RoutedEventArgs e)
+    {
+        FolderPicker picker = CreateFolderPicker();
+        var folder = await picker.PickSingleFolderAsync();
+        if (folder is not null)
+            SourceSearchFolderBox.Text = folder.Path;
+    }
+
     private async void BrowseFfmpeg_Click(object sender, RoutedEventArgs e)
     {
         FileOpenPicker picker = CreateFileOpenPicker();
@@ -327,13 +385,16 @@ public sealed partial class MainPage : Page
         {
             _keepRenderOutput = true;
             UpdateProgress(new(RenderProgressBar.Value, "Cancelled", "The render was cancelled."));
+            RenderNotifier.ShowCancelled();
         }
         catch (Exception exception)
         {
             _keepRenderOutput = true;
             AppendLog("ERROR: " + exception);
             StageText.Text = "Failed";
-            await ShowMessageAsync("Render failed", UserFacingErrors.Summarize(exception));
+            string summary = UserFacingErrors.Summarize(exception);
+            RenderNotifier.ShowFailed(summary);
+            await ShowMessageAsync("Render failed", summary);
         }
         finally
         {
@@ -353,6 +414,7 @@ public sealed partial class MainPage : Page
         _lastRenderedFile = Path.Combine(settings.OutputDirectory, settings.OutputName + "_final.mp4");
         OpenOutputButton.IsEnabled = true;
         PreviewRenderedButton.IsEnabled = File.Exists(_lastRenderedFile);
+        RenderNotifier.ShowCompleted(shorts: false);
         await ShowMessageAsync("Render complete", "The AmiReel render completed successfully.");
     }
 
@@ -366,6 +428,7 @@ public sealed partial class MainPage : Page
         ShortOutputBox.Text = settings.OutputPath;
         OpenOutputButton.IsEnabled = true;
         PreviewRenderedButton.IsEnabled = File.Exists(_lastRenderedFile);
+        RenderNotifier.ShowCompleted(shorts: true);
         await ShowMessageAsync("Short complete", "The YouTube Short was rendered successfully.");
     }
 
@@ -432,6 +495,27 @@ public sealed partial class MainPage : Page
             EndCardHoldSeconds = Number(HoldBox.Text, "end-card hold"),
             ThumbnailInterval = interval,
             MoveSourcesToOriginals = MoveSourcesBox.IsChecked == true,
+            SourceCropMode = SelectedVideoCropMode(),
+            CropLeft = ParseNonNegativeInt(VideoCropLeftBox.Text, "Crop left"),
+            CropRight = ParseNonNegativeInt(VideoCropRightBox.Text, "Crop right"),
+            CropTop = ParseNonNegativeInt(VideoCropTopBox.Text, "Crop top"),
+            CropBottom = ParseNonNegativeInt(VideoCropBottomBox.Text, "Crop bottom"),
+        };
+    }
+
+    private RenderSettings ReadVideoPreviewSettings()
+    {
+        IReadOnlyList<string> inputs = InputList.SelectedItem is string selected
+            ? [selected]
+            : _inputs.ToList();
+
+        return ReadSettings() with
+        {
+            InputFiles = inputs.ToList(),
+            OutputDirectory = string.IsNullOrWhiteSpace(OutputFolderBox.Text)
+                ? Path.GetTempPath()
+                : OutputFolderBox.Text.Trim(),
+            OutputName = string.IsNullOrWhiteSpace(OutputNameBox.Text) ? "preview" : OutputNameBox.Text.Trim(),
         };
     }
 
@@ -599,6 +683,49 @@ public sealed partial class MainPage : Page
             ShortFontBox.Text = file.Path;
     }
 
+    private async void OpenVideoCropEditor_Click(object sender, RoutedEventArgs e)
+    {
+        string? input = InputList.SelectedItem as string ?? _inputs.FirstOrDefault();
+        if (string.IsNullOrWhiteSpace(input) || !File.Exists(input))
+        {
+            await ShowMessageAsync("Crop source", "Select a valid source video first.");
+            return;
+        }
+
+        try
+        {
+            CropEditorDialog.XamlRoot = XamlRoot;
+            CropEditorDialog.RequestedTheme = ActualTheme;
+            double duration = 30;
+            double trimStart = 0;
+            try { trimStart = ParseNonNegativeNumber(TrimBox.Text, "trim start"); } catch (ArgumentException) { }
+
+            await ShortCropEditor.LoadVideoFrameAsync(
+                input,
+                RenderPipeline.FormatTimestamp(trimStart),
+                duration,
+                FfmpegPathBox.Text.Trim(),
+                FfprobePathBox.Text.Trim(),
+                CancellationToken.None);
+            ShortCropEditor.SetInsets(ReadVideoCropInsets());
+
+            ContentDialogResult result = await CropEditorDialog.ShowAsync();
+            if (result != ContentDialogResult.Primary)
+                return;
+
+            PixelInsets insets = ShortCropEditor.Insets;
+            VideoCropLeftBox.Text = insets.Left.ToString(CultureInfo.InvariantCulture);
+            VideoCropRightBox.Text = insets.Right.ToString(CultureInfo.InvariantCulture);
+            VideoCropTopBox.Text = insets.Top.ToString(CultureInfo.InvariantCulture);
+            VideoCropBottomBox.Text = insets.Bottom.ToString(CultureInfo.InvariantCulture);
+            _ = RefreshVideoPreviewAsync(automatic: true);
+        }
+        catch (Exception exception)
+        {
+            await ShowMessageAsync("Crop source", UserFacingErrors.Summarize(exception));
+        }
+    }
+
     private async void OpenCropEditor_Click(object sender, RoutedEventArgs e)
     {
         string input = ShortInputBox.Text.Trim();
@@ -656,6 +783,22 @@ public sealed partial class MainPage : Page
             ReadBox(ShortCropBottomBox.Text));
     }
 
+    private PixelInsets ReadVideoCropInsets()
+    {
+        static int ReadBox(string text)
+        {
+            return int.TryParse(text, NumberStyles.Integer, CultureInfo.InvariantCulture, out int value) && value > 0
+                ? value
+                : 0;
+        }
+
+        return new PixelInsets(
+            ReadBox(VideoCropLeftBox.Text),
+            ReadBox(VideoCropRightBox.Text),
+            ReadBox(VideoCropTopBox.Text),
+            ReadBox(VideoCropBottomBox.Text));
+    }
+
     private async void PreviewShortSource_Click(object sender, RoutedEventArgs e)
     {
         if (!string.IsNullOrWhiteSpace(ShortInputBox.Text))
@@ -665,6 +808,56 @@ public sealed partial class MainPage : Page
     private async void UpdateShortPreview_Click(object sender, RoutedEventArgs e) =>
         await RefreshShortPreviewAsync(automatic: false);
 
+    private async void UpdateVideoPreview_Click(object sender, RoutedEventArgs e) =>
+        await RefreshVideoPreviewAsync(automatic: false);
+
+    private async Task RefreshVideoPreviewAsync(bool automatic)
+    {
+        if (_isRendering)
+            return;
+
+        int generation = ++_previewGeneration;
+        VideoPreviewProgress.Visibility = Visibility.Visible;
+        UpdateVideoPreviewButton.IsEnabled = false;
+        VideoPreviewStatusText.Text = "Rendering 16:9 preview frames...";
+
+        try
+        {
+            RenderSettings settings = ReadVideoPreviewSettings();
+            RenderPipeline.ValidatePreview(settings);
+            _videoPreviewDirectory ??= Path.Combine(Path.GetTempPath(), "AmiReel", "video-preview", Guid.NewGuid().ToString("N"));
+            Directory.CreateDirectory(_videoPreviewDirectory);
+
+            VideoPreviewFrames frames = await new RenderPipeline().RenderPreviewAsync(
+                settings, _videoPreviewDirectory, _ => { }, CancellationToken.None);
+
+            if (generation != _previewGeneration)
+                return;
+
+            VideoPreviewOpeningImage.Source = await LoadPreviewBitmapAsync(frames.OpeningPath, 584);
+            VideoPreviewClosingImage.Source = await LoadPreviewBitmapAsync(frames.ClosingPath, 584);
+            VideoPreviewStatusText.Text = "4K look · cropped source and end card";
+        }
+        catch (Exception exception)
+        {
+            if (generation != _previewGeneration)
+                return;
+
+            string message = UserFacingErrors.Summarize(exception);
+            VideoPreviewStatusText.Text = message;
+            if (!automatic)
+                await ShowMessageAsync("Preview failed", message);
+        }
+        finally
+        {
+            if (generation == _previewGeneration)
+            {
+                VideoPreviewProgress.Visibility = Visibility.Collapsed;
+                UpdateVideoPreviewButton.IsEnabled = true;
+            }
+        }
+    }
+
     private async Task RefreshShortPreviewAsync(bool automatic)
     {
         if (_isRendering)
@@ -688,8 +881,8 @@ public sealed partial class MainPage : Page
             if (generation != _previewGeneration)
                 return;
 
-            ShortPreviewOpeningImage.Source = await LoadPreviewBitmapAsync(frames.OpeningPath);
+            ShortPreviewOpeningImage.Source = await LoadPreviewBitmapAsync(frames.OpeningPath, 296);
-            ShortPreviewClosingImage.Source = await LoadPreviewBitmapAsync(frames.ClosingPath);
+            ShortPreviewClosingImage.Source = await LoadPreviewBitmapAsync(frames.ClosingPath, 296);
             bool hasFont = !string.IsNullOrWhiteSpace(settings.FontFile) && File.Exists(settings.FontFile);
             ShortPreviewStatusText.Text = hasFont
                 ? $"{settings.Style} · opening hook and closing title card"
@@ -715,10 +908,10 @@ public sealed partial class MainPage : Page
         }
     }
 
-    private static async Task<BitmapImage> LoadPreviewBitmapAsync(string path)
+    private static async Task<BitmapImage> LoadPreviewBitmapAsync(string path, int decodePixelWidth)
     {
         await using FileStream stream = File.OpenRead(path);
-        BitmapImage bitmap = new() { DecodePixelWidth = 296 };
+        BitmapImage bitmap = new() { DecodePixelWidth = decodePixelWidth };
         await bitmap.SetSourceAsync(stream.AsRandomAccessStream());
         return bitmap;
     }
@@ -814,10 +1007,38 @@ public sealed partial class MainPage : Page
                 return;
 
             LogBox.Text += chunk;
-            LogBox.Select(LogBox.Text.Length, 0);
+            ScrollLogToEnd();
         });
     }
 
+    private void ScrollLogToEnd()
+    {
+        LogBox.SelectionStart = LogBox.Text.Length;
+        LogBox.SelectionLength = 0;
+        if (FindDescendantScrollViewer(LogBox) is not ScrollViewer viewer)
+            return;
+
+        viewer.UpdateLayout();
+        double offset = Math.Max(0, viewer.ExtentHeight - viewer.ViewportHeight);
+        viewer.ChangeView(null, offset, null, disableAnimation: true);
+    }
+
+    private static ScrollViewer? FindDescendantScrollViewer(DependencyObject root)
+    {
+        if (root is ScrollViewer viewer)
+            return viewer;
+
+        int count = VisualTreeHelper.GetChildrenCount(root);
+        for (int index = 0; index < count; index++)
+        {
+            ScrollViewer? match = FindDescendantScrollViewer(VisualTreeHelper.GetChild(root, index));
+            if (match is not null)
+                return match;
+        }
+
+        return null;
+    }
+
     private void SaveSettings()
     {
         AppSettingsStore.Save(new AppSettings
@@ -834,6 +1055,12 @@ public sealed partial class MainPage : Page
             EndCardHoldSeconds = HoldBox.Text.Trim(),
             ThumbnailInterval = IntervalBox.Text.Trim(),
             MoveSourcesToOriginals = MoveSourcesBox.IsChecked == true,
+            SourceSearchFolder = SourceSearchFolderBox.Text.Trim(),
+            VideoSourceCropMode = SelectedVideoCropMode().ToString(),
+            VideoCropLeft = VideoCropLeftBox.Text.Trim(),
+            VideoCropRight = VideoCropRightBox.Text.Trim(),
+            VideoCropTop = VideoCropTopBox.Text.Trim(),
+            VideoCropBottom = VideoCropBottomBox.Text.Trim(),
             ShortsStyle = SelectedShortStyle(),
             ShortsHook = ShortHookBox.Text.Trim(),
             ShortsWebsite = ShortWebsiteBox.Text.Trim(),
@@ -869,6 +1096,12 @@ public sealed partial class MainPage : Page
         return Enum.TryParse(tag, ignoreCase: true, out ShortSourceCropMode mode) ? mode : ShortSourceCropMode.Auto;
     }
 
+    private ShortSourceCropMode SelectedVideoCropMode()
+    {
+        string tag = (VideoCropModeBox.SelectedItem as ComboBoxItem)?.Tag?.ToString() ?? "Auto";
+        return Enum.TryParse(tag, ignoreCase: true, out ShortSourceCropMode mode) ? mode : ShortSourceCropMode.Auto;
+    }
+
     private string SelectedShortPreset() => (ShortPresetBox.SelectedItem as ComboBoxItem)?.Tag?.ToString() ?? "slow";
 
     private void SelectTheme(string theme) => SelectComboTag(ThemeBox, theme);

Models/AppSettings.cs

@@ -21,6 +21,12 @@ public sealed record AppSettings
     public required string EndCardHoldSeconds { get; init; }
     public required string ThumbnailInterval { get; init; }
     public bool? MoveSourcesToOriginals { get; init; }
+    public string SourceSearchFolder { get; init; } = "";
+    public string VideoSourceCropMode { get; init; } = "Auto";
+    public string VideoCropLeft { get; init; } = "0";
+    public string VideoCropRight { get; init; } = "0";
+    public string VideoCropTop { get; init; } = "0";
+    public string VideoCropBottom { get; init; } = "0";
 
     // Shorts tab defaults (sticky across launches, same as the fields above).
     public string ShortsStyle { get; init; } = "Brand";
@@ -57,6 +63,12 @@ public sealed record AppSettings
         EndCardHoldSeconds = "4",
         ThumbnailInterval = "10",
         MoveSourcesToOriginals = true,
+        SourceSearchFolder = "",
+        VideoSourceCropMode = "Auto",
+        VideoCropLeft = "0",
+        VideoCropRight = "0",
+        VideoCropTop = "0",
+        VideoCropBottom = "0",
     };
 
     public AppSettings Normalize(string fallbackOutputFolder) => this with
@@ -73,6 +85,12 @@ public sealed record AppSettings
         EndCardHoldSeconds = string.IsNullOrWhiteSpace(EndCardHoldSeconds) ? "4" : EndCardHoldSeconds,
         ThumbnailInterval = string.IsNullOrWhiteSpace(ThumbnailInterval) ? "10" : ThumbnailInterval,
         MoveSourcesToOriginals = MoveSourcesToOriginals ?? true,
+        SourceSearchFolder = SourceSearchFolder ?? "",
+        VideoSourceCropMode = string.IsNullOrWhiteSpace(VideoSourceCropMode) ? "Auto" : VideoSourceCropMode,
+        VideoCropLeft = string.IsNullOrWhiteSpace(VideoCropLeft) ? "0" : VideoCropLeft,
+        VideoCropRight = string.IsNullOrWhiteSpace(VideoCropRight) ? "0" : VideoCropRight,
+        VideoCropTop = string.IsNullOrWhiteSpace(VideoCropTop) ? "0" : VideoCropTop,
+        VideoCropBottom = string.IsNullOrWhiteSpace(VideoCropBottom) ? "0" : VideoCropBottom,
         ShortsStyle = string.IsNullOrWhiteSpace(ShortsStyle) ? "Brand" : ShortsStyle,
         ShortsHook = ShortsHook ?? "THIS RAN ON AN AMIGA",
         ShortsWebsite = ShortsWebsite ?? "AMIGADB.NET",

Models/RenderSettings.cs

@@ -29,6 +29,11 @@ public sealed record RenderSettings
     public required double EndCardHoldSeconds { get; init; }
     public required int ThumbnailInterval { get; init; }
     public bool MoveSourcesToOriginals { get; init; } = true;
+    public ShortSourceCropMode SourceCropMode { get; init; } = ShortSourceCropMode.Auto;
+    public int CropLeft { get; init; }
+    public int CropRight { get; init; }
+    public int CropTop { get; init; }
+    public int CropBottom { get; init; }
     public int Width { get; init; } = 3840;
     public int Height { get; init; } = 2160;
     public int FramesPerSecond { get; init; } = 50;
@@ -37,3 +42,13 @@ public sealed record RenderSettings
 }
 
 public sealed record RenderProgress(double Percent, string Stage, string Message);
+
+/// <summary>Which moment of a long-form video a preview still represents.</summary>
+public enum VideoPreviewShot
+{
+    Opening,
+    Closing,
+}
+
+/// <summary>PNG stills of the cropped 4K source look and the end card.</summary>
+public sealed record VideoPreviewFrames(string OpeningPath, string ClosingPath);

Models/ShortSettings.cs

@@ -25,9 +25,10 @@ public enum ShortStyle
     Video,
 }
 
-/// <summary>How the video style crops the Amiga source before overlaying it.</summary>
+/// <summary>How the Amiga source is cropped before it is scaled into the output.</summary>
 public enum ShortSourceCropMode
 {
+    None,
     Auto,
     Center,
 }

Package.appxmanifest

@@ -5,7 +5,9 @@
   xmlns:mp="http://schemas.microsoft.com/appx/2014/phone/manifest"
   xmlns:uap="http://schemas.microsoft.com/appx/manifest/uap/windows10"
   xmlns:rescap="http://schemas.microsoft.com/appx/manifest/foundation/windows10/restrictedcapabilities"
-  IgnorableNamespaces="uap rescap">
+  xmlns:com="http://schemas.microsoft.com/appx/manifest/com/windows10"
+  xmlns:desktop="http://schemas.microsoft.com/appx/manifest/desktop/windows10"
+  IgnorableNamespaces="uap rescap com desktop">
 
   <Identity
     Name="F004AE73-5989-46F3-B913-E9A3A355713F"
@@ -42,6 +44,18 @@
         <uap:DefaultTile Wide310x150Logo="Assets\Wide310x150Logo.png" />
         <uap:SplashScreen Image="Assets\SplashScreen.png" BackgroundColor="#0E1525" />
       </uap:VisualElements>
+      <Extensions>
+        <desktop:Extension Category="windows.toastNotificationActivation">
+          <desktop:ToastNotificationActivation ToastActivatorCLSID="F004AE73-5989-46F3-B913-E9A3A3557140" />
+        </desktop:Extension>
+        <com:Extension Category="windows.comServer">
+          <com:ComServer>
+            <com:ExeServer Executable="AmiReel.exe" DisplayName="AmiReel" Arguments="----AppNotificationActivated:">
+              <com:Class Id="F004AE73-5989-46F3-B913-E9A3A3557140" />
+            </com:ExeServer>
+          </com:ComServer>
+        </com:Extension>
+      </Extensions>
     </Application>
   </Applications>
 

Services/FfmpegOutputFilter.cs

@@ -33,6 +33,7 @@ public static class FfmpegOutputFilter
         "other streams:",
         "global headers:",
         "muxing overhead:",
+        "Last message repeated",
     ];
 
     public static bool IsBoilerplateLine(string line) =>

Services/RenderNotifier.cs

@@ -0,0 +1,66 @@
+using Microsoft.Windows.AppNotifications;
+using Microsoft.Windows.AppNotifications.Builder;
+
+namespace AmiReel.Services;
+
+/// <summary>Shows a Windows app notification when a Video or Shorts render finishes, fails, or is cancelled.</summary>
+public static class RenderNotifier
+{
+    public static void Register()
+    {
+        try
+        {
+            AppNotificationManager.Default.NotificationInvoked -= OnNotificationInvoked;
+            AppNotificationManager.Default.NotificationInvoked += OnNotificationInvoked;
+            AppNotificationManager.Default.Register();
+        }
+        catch
+        {
+            // Notifications are unavailable when the process is elevated or has no identity.
+        }
+    }
+
+    public static void ShowCompleted(bool shorts) => Show(DescribeCompleted(shorts));
+
+    public static void ShowFailed(string summary) => Show(DescribeFailed(summary));
+
+    public static void ShowCancelled() => Show(DescribeCancelled());
+
+    internal static (string Title, string Body) DescribeCompleted(bool shorts) => shorts
+        ? ("Short complete", "The YouTube Short was rendered successfully.")
+        : ("Render complete", "The AmiReel render completed successfully.");
+
+    internal static (string Title, string Body) DescribeFailed(string summary)
+    {
+        string body = string.IsNullOrWhiteSpace(summary)
+            ? "The render failed."
+            : summary.ReplaceLineEndings(" ");
+        if (body.Length > 180)
+            body = body[..177] + "...";
+        return ("Render failed", body);
+    }
+
+    internal static (string Title, string Body) DescribeCancelled() =>
+        ("Render cancelled", "The render was cancelled.");
+
+    private static void Show((string Title, string Body) content)
+    {
+        try
+        {
+            AppNotification notification = new AppNotificationBuilder()
+                .AddText(content.Title)
+                .AddText(content.Body)
+                .BuildNotification();
+            AppNotificationManager.Default.Show(notification);
+        }
+        catch
+        {
+            // Show fails silently when notifications are unsupported.
+        }
+    }
+
+    private static void OnNotificationInvoked(AppNotificationManager sender, AppNotificationActivatedEventArgs args)
+    {
+        App.MainWindowInstance?.DispatcherQueue.TryEnqueue(() => App.MainWindowInstance.Activate());
+    }
+}

Services/RenderPipeline.cs

@@ -43,8 +43,9 @@ public sealed class RenderPipeline
             double joinDuration = await ProbeCombinedDurationAsync(probe, tools, settings.InputFiles, token);
 
             progress.Report(new(2, "Joining recordings", "Creating the 4K 50 FPS intermediate video"));
+            string cropFilter = await ResolveSourceCropFilterAsync(tools, settings, log, token);
             List<string> joinArgs = ["-y", "-f", "concat", "-safe", "0", "-i", concat,
-                "-vf", $"scale=2880:2160:flags=lanczos:force_original_aspect_ratio=decrease,pad={settings.Width}:{settings.Height}:(ow-iw)/2:(oh-ih)/2,format=yuv420p",
+                "-vf", BuildJoinVideoFilter(settings, cropFilter),
                 "-r", settings.FramesPerSecond.ToString(CultureInfo.InvariantCulture)];
             joinArgs.AddRange(EncoderArguments(encoder));
             joinArgs.AddRange(["-c:a", "aac", "-b:a", "384k", "-ar", "48000", main]);
@@ -122,6 +123,64 @@ public sealed class RenderPipeline
         }
     }
 
+    /// <summary>
+    /// Renders two 16:9 stills with the same crop/scale/pad as the final video: a source frame and the end card.
+    /// </summary>
+    public async Task<VideoPreviewFrames> RenderPreviewAsync(
+        RenderSettings settings, string outputDirectory, Action<string> log, CancellationToken token)
+    {
+        ValidatePreview(settings);
+        ToolPaths tools = await ToolExtractor.ResolveAsync(settings.FfmpegPath, settings.FfprobePath, token);
+        Directory.CreateDirectory(outputDirectory);
+
+        string cropFilter = await ResolveSourceCropFilterAsync(tools, settings, log, token);
+        string joinFilter = BuildJoinVideoFilter(settings, cropFilter);
+        string openingPath = Path.Combine(outputDirectory, "opening.png");
+        string closingPath = Path.Combine(outputDirectory, "closing.png");
+
+        MediaProbe probe = new(_runner, log);
+        string previewInput = settings.InputFiles[0];
+        double duration = 0;
+        try
+        {
+            duration = await probe.ProbeDurationAsync(tools, previewInput, token);
+        }
+        catch (Exception exception)
+        {
+            log($"WARNING: Could not probe source duration: {exception.Message}");
+        }
+
+        double seek = PreviewSeekSeconds(settings.TrimStart, duration);
+        log($"Preview opening frame at {F(seek)}s...");
+        await _runner.RunAsync(
+            tools.Ffmpeg,
+            [
+                "-hide_banner", "-y", "-ss", F(seek), "-i", previewInput,
+                "-frames:v", "1", "-update", "1", "-vf", joinFilter, openingPath,
+            ],
+            log,
+            null,
+            token);
+
+        string workDir = Path.Combine(outputDirectory, "meta");
+        Directory.CreateDirectory(workDir);
+        string endCardPath = await ResolveEndCardPathAsync(settings, workDir, token);
+        log("Preview end-card frame...");
+        await _runner.RunAsync(
+            tools.Ffmpeg,
+            [
+                "-hide_banner", "-y", "-loop", "1", "-i", endCardPath,
+                "-frames:v", "1", "-update", "1",
+                "-vf", $"scale={settings.Width}:{settings.Height}:force_original_aspect_ratio=decrease,pad={settings.Width}:{settings.Height}:(ow-iw)/2:(oh-ih)/2,format=yuv420p",
+                closingPath,
+            ],
+            log,
+            null,
+            token);
+
+        return new VideoPreviewFrames(openingPath, closingPath);
+    }
+
     private async Task<string> SelectEncoderAsync(ToolPaths tools, EncoderMode requested, Action<string> log, CancellationToken token)
     {
         if (requested == EncoderMode.CpuX264) return "x264";
@@ -360,16 +419,93 @@ public sealed class RenderPipeline
 
     internal static void Validate(RenderSettings s)
     {
-        if (s.InputFiles.Count == 0) throw new ArgumentException("Select at least one video input file.");
+        ValidatePreview(s);
-        if (s.InputFiles.Any(f => !File.Exists(f))) throw new FileNotFoundException("One or more input files no longer exist.");
-        if (!string.IsNullOrWhiteSpace(s.EndCardPath) && !File.Exists(s.EndCardPath))
-            throw new FileNotFoundException("End-card image was not found.");
         if (string.IsNullOrWhiteSpace(s.OutputDirectory)) throw new ArgumentException("Select an output directory.");
         if (string.IsNullOrWhiteSpace(s.OutputName) || s.OutputName.IndexOfAny(Path.GetInvalidFileNameChars()) >= 0)
             throw new ArgumentException("Enter a valid output name.");
         if (s.ThumbnailInterval < 1) throw new ArgumentException("Thumbnail interval must be at least one second.");
     }
 
+    internal static void ValidatePreview(RenderSettings s)
+    {
+        if (s.InputFiles.Count == 0) throw new ArgumentException("Select at least one video input file.");
+        if (s.InputFiles.Any(f => !File.Exists(f))) throw new FileNotFoundException("One or more input files no longer exist.");
+        if (!string.IsNullOrWhiteSpace(s.EndCardPath) && !File.Exists(s.EndCardPath))
+            throw new FileNotFoundException("End-card image was not found.");
+        if (s.CropLeft < 0 || s.CropRight < 0 || s.CropTop < 0 || s.CropBottom < 0)
+            throw new ArgumentException("Manual crop values must be non-negative.");
+    }
+
+    internal static string BuildJoinVideoFilter(RenderSettings settings, string cropFilter) =>
+        SourceCropFilters.Prefix(
+            cropFilter,
+            $"scale=2880:2160:flags=lanczos:force_original_aspect_ratio=decrease,pad={settings.Width}:{settings.Height}:(ow-iw)/2:(oh-ih)/2,format=yuv420p");
+
+    internal static string BuildSourceCropFilter(RenderSettings settings, string? autoDetected) =>
+        SourceCropFilters.Resolve(
+            settings.SourceCropMode,
+            settings.CropLeft,
+            settings.CropRight,
+            settings.CropTop,
+            settings.CropBottom,
+            autoDetected);
+
+    internal static double PreviewSeekSeconds(double trimStart, double durationSeconds)
+    {
+        double start = Math.Max(0, trimStart);
+        if (durationSeconds <= start)
+            return start;
+
+        double remaining = durationSeconds - start;
+        return start + Math.Min(1.2, Math.Max(0, remaining * 0.2));
+    }
+
+    internal static string FormatTimestamp(double seconds) =>
+        TimeSpan.FromSeconds(Math.Max(0, seconds)).ToString(@"hh\:mm\:ss\.fff", CultureInfo.InvariantCulture);
+
+    private async Task<string> ResolveSourceCropFilterAsync(
+        ToolPaths tools, RenderSettings settings, Action<string> log, CancellationToken token)
+    {
+        string? detected = null;
+        if (!SourceCropFilters.HasManualCrop(settings.CropLeft, settings.CropRight, settings.CropTop, settings.CropBottom)
+            && settings.SourceCropMode == ShortSourceCropMode.Auto)
+        {
+            detected = await DetectHorizontalCropAsync(tools, settings, log, token);
+            if (detected is null)
+                log("Warning: could not auto-detect left/right source black borders; using centered 4:3 crop.");
+        }
+        else if (SourceCropFilters.HasManualCrop(settings.CropLeft, settings.CropRight, settings.CropTop, settings.CropBottom))
+        {
+            log($"Source crop: manual L={settings.CropLeft} R={settings.CropRight} T={settings.CropTop} B={settings.CropBottom}");
+        }
+        else if (settings.SourceCropMode == ShortSourceCropMode.None)
+        {
+            log("Source crop: none");
+        }
+        else
+        {
+            log("Source crop: centered 4:3");
+        }
+
+        return BuildSourceCropFilter(settings, detected);
+    }
+
+    private async Task<string?> DetectHorizontalCropAsync(
+        ToolPaths tools, RenderSettings settings, Action<string> log, CancellationToken token)
+    {
+        string input = settings.InputFiles[0];
+        List<string> args = SourceCropFilters.BuildHorizontalCropDetectArguments(
+            input, FormatTimestamp(settings.TrimStart), 4);
+
+        string output = await _runner.RunAsync(tools.Ffmpeg, args, log, null, token, allowFailure: true);
+        string? filter = SourceCropFilters.TryBuildAutoHorizontalFilter(output);
+        if (filter is null)
+            return null;
+
+        log($"Source crop: {filter} (auto left/right black crop)");
+        return filter;
+    }
+
     private static string EscapeConcat(string path) => path.Replace("'", "'\\''");
     private static string F(double value) => value.ToString("0.###", CultureInfo.InvariantCulture);
 }

Services/ShortsPipeline.cs

@@ -1,7 +1,6 @@
 using System.Globalization;
 using System.IO;
 using System.Text;
-using System.Text.RegularExpressions;
 using AmiReel.Models;
 
 namespace AmiReel.Services;
@@ -13,12 +12,7 @@ namespace AmiReel.Services;
 /// </summary>
 public sealed class ShortsPipeline
 {
-    internal const string DefaultSourceCropFilter =
+    internal const string DefaultSourceCropFilter = SourceCropFilters.CenterFourByThreeFilter;
-        "crop='min(iw,ih*4/3)':'min(ih,iw*3/4)':'(iw-ow)/2':'(ih-oh)/2'";
-
-    private static readonly Regex CropSpecRegex = new(
-        @"crop=(\d+):(\d+):(\d+):(\d+)",
-        RegexOptions.CultureInvariant);
 
     private readonly ProcessRunner _runner = new();
 
@@ -421,7 +415,7 @@ public sealed class ShortsPipeline
         $"scale={SourceTargetWidth(sourceMarginX)}:-2:flags=lanczos";
 
     internal static string BuildManualCropFilter(int left, int right, int top, int bottom) =>
-        $"crop=iw-{left}-{right}:ih-{top}-{bottom}:{left}:{top}";
+        SourceCropFilters.BuildManualCropFilter(left, right, top, bottom);
 
     internal static string BuildVideoBaseFilter(string cropFilter, string scaleFilter, double blur, double opacity)
     {
@@ -430,49 +424,18 @@ public sealed class ShortsPipeline
             "color=c=black:s=1080x1920:r=50[black];" +
             $"[1:v]scale=1080:1920:force_original_aspect_ratio=increase,crop=1080:1920,setsar=1{blurFilter},format=rgba,colorchannelmixer=aa={F(opacity)}[bgvideo];" +
             "[black][bgvideo]overlay=x=0:y=0:format=auto[bg];" +
-            $"[0:v]{cropFilter},{scaleFilter},setsar=1[fg];" +
+            $"[0:v]{SourceCropFilters.Prefix(cropFilter, scaleFilter)},setsar=1[fg];" +
             "[bg][fg]overlay=x=(W-w)/2:y=(H-h)/2:format=auto[base]";
     }
 
-    internal static string? SelectMostCommonCropSpec(string ffmpegOutput)
+    internal static string? SelectMostCommonCropSpec(string ffmpegOutput) =>
-    {
+        SourceCropFilters.SelectMostCommonCropSpec(ffmpegOutput);
-        Dictionary<string, int> counts = new(StringComparer.Ordinal);
-        foreach (Match match in CropSpecRegex.Matches(ffmpegOutput))
-        {
-            string spec = match.Value;
-            counts[spec] = counts.GetValueOrDefault(spec) + 1;
-        }
 
-        return counts.Count == 0
+    internal static bool TryParseCropSpec(string spec, out int width, out int height, out int x, out int y) =>
-            ? null
+        SourceCropFilters.TryParseCropSpec(spec, out width, out height, out x, out y);
-            : counts.OrderByDescending(pair => pair.Value).ThenBy(pair => pair.Key, StringComparer.Ordinal).First().Key;
-    }
 
-    internal static bool TryParseCropSpec(string spec, out int width, out int height, out int x, out int y)
+    internal static bool TryBuildAutoHorizontalCrop(int detectedWidth, int detectedX, out int width, out int x) =>
-    {
+        SourceCropFilters.TryBuildAutoHorizontalCrop(detectedWidth, detectedX, out width, out x);
-        Match match = CropSpecRegex.Match(spec);
-        if (!match.Success)
-        {
-            width = height = x = y = 0;
-            return false;
-        }
-
-        width = int.Parse(match.Groups[1].Value, CultureInfo.InvariantCulture);
-        height = int.Parse(match.Groups[2].Value, CultureInfo.InvariantCulture);
-        x = int.Parse(match.Groups[3].Value, CultureInfo.InvariantCulture);
-        y = int.Parse(match.Groups[4].Value, CultureInfo.InvariantCulture);
-        return true;
-    }
-
-    internal static bool TryBuildAutoHorizontalCrop(int detectedWidth, int detectedX, out int width, out int x)
-    {
-        int inset = (int)(detectedWidth * 0.005 / 2) * 2;
-        width = ((detectedWidth - (2 * inset)) / 2) * 2;
-        x = ((detectedX + inset) / 2) * 2;
-        if (width < 16)
-            return false;
-        return true;
-    }
 
     private async Task<string> ResolveBaseFilterAsync(
         ToolPaths tools, ShortSettings settings, Action<string> log, CancellationToken token)
@@ -480,33 +443,36 @@ public sealed class ShortsPipeline
         if (settings.Style != ShortStyle.Video)
             return GetBaseFilter(settings.Style);
 
-        string cropFilter = DefaultSourceCropFilter;
         string scaleFilter = BuildSourceScaleFilter(settings.SourceMarginX);
-        bool hasManualCrop = settings.CropLeft > 0 || settings.CropRight > 0
+        string? detected = null;
-            || settings.CropTop > 0 || settings.CropBottom > 0;
+        if (!SourceCropFilters.HasManualCrop(settings.CropLeft, settings.CropRight, settings.CropTop, settings.CropBottom)
-
+            && settings.SourceCropMode == ShortSourceCropMode.Auto)
-        if (hasManualCrop)
-        {
-            cropFilter = BuildManualCropFilter(settings.CropLeft, settings.CropRight, settings.CropTop, settings.CropBottom);
-            log($"Source crop: manual L={settings.CropLeft} R={settings.CropRight} T={settings.CropTop} B={settings.CropBottom}");
-        }
-        else if (settings.SourceCropMode == ShortSourceCropMode.Auto)
-        {
-            string? detected = await DetectHorizontalCropAsync(tools, settings, log, token);
-            if (detected is not null)
-            {
-                cropFilter = detected;
-            }
-            else
         {
+            detected = await DetectHorizontalCropAsync(tools, settings, log, token);
+            if (detected is null)
                 log("Warning: could not auto-detect left/right source black borders; using centered 4:3 crop.");
         }
+        else if (SourceCropFilters.HasManualCrop(settings.CropLeft, settings.CropRight, settings.CropTop, settings.CropBottom))
+        {
+            log($"Source crop: manual L={settings.CropLeft} R={settings.CropRight} T={settings.CropTop} B={settings.CropBottom}");
+        }
+        else if (settings.SourceCropMode == ShortSourceCropMode.None)
+        {
+            log("Source crop: none");
         }
         else
         {
             log("Source crop: centered 4:3");
         }
 
+        string cropFilter = SourceCropFilters.Resolve(
+            settings.SourceCropMode,
+            settings.CropLeft,
+            settings.CropRight,
+            settings.CropTop,
+            settings.CropBottom,
+            detected);
+
         return BuildVideoBaseFilter(cropFilter, scaleFilter, settings.VideoBlur, settings.VideoOpacity);
     }
 
@@ -514,27 +480,16 @@ public sealed class ShortsPipeline
         ToolPaths tools, ShortSettings settings, Action<string> log, CancellationToken token)
     {
         double detectDuration = Math.Clamp(settings.DurationSeconds < 4 ? settings.DurationSeconds : 4, 0.5, 4);
-        List<string> args =
+        List<string> args = SourceCropFilters.BuildHorizontalCropDetectArguments(
-        [
+            settings.InputFile, settings.Start, detectDuration);
-            "-hide_banner",
-            "-ss", settings.Start,
-            "-t", F(detectDuration),
-            "-i", settings.InputFile,
-            "-an",
-            "-vf", "crop=iw:trunc(ih*0.70/2)*2:0:trunc(ih*0.15/2)*2,cropdetect=limit=28:round=2:reset=0",
-            "-f", "null",
-            "-",
-        ];
 
         string output = await _runner.RunAsync(tools.Ffmpeg, args, log, null, token, allowFailure: true);
-        string? spec = SelectMostCommonCropSpec(output);
+        string? filter = SourceCropFilters.TryBuildAutoHorizontalFilter(output);
-        if (spec is null || !TryParseCropSpec(spec, out int width, out _, out int x, out _))
+        if (filter is null)
-            return null;
-        if (!TryBuildAutoHorizontalCrop(width, x, out int cropWidth, out int cropX))
             return null;
 
-        log($"Source crop: w={cropWidth}, x={cropX} (auto left/right black crop)");
+        log($"Source crop: {filter} (auto left/right black crop)");
-        return $"crop={cropWidth}:ih:{cropX}:0";
+        return filter;
     }
 
     internal static string GetBaseFilter(ShortStyle style) => style switch

Services/SourceCropFilters.cs

@@ -0,0 +1,113 @@
+using System.Globalization;
+using System.Text.RegularExpressions;
+using AmiReel.Models;
+
+namespace AmiReel.Services;
+
+/// <summary>Shared FFmpeg crop filters used by both Video and Shorts pipelines.</summary>
+internal static class SourceCropFilters
+{
+    internal const string CenterFourByThreeFilter =
+        "crop='min(iw,ih*4/3)':'min(ih,iw*3/4)':'(iw-ow)/2':'(ih-oh)/2'";
+
+    private static readonly Regex CropSpecRegex = new(
+        @"crop=(\d+):(\d+):(\d+):(\d+)",
+        RegexOptions.CultureInvariant);
+
+    internal static string BuildManualCropFilter(int left, int right, int top, int bottom) =>
+        $"crop=iw-{left}-{right}:ih-{top}-{bottom}:{left}:{top}";
+
+    internal static bool HasManualCrop(int left, int right, int top, int bottom) =>
+        left > 0 || right > 0 || top > 0 || bottom > 0;
+
+    internal static string Resolve(
+        ShortSourceCropMode mode,
+        int left,
+        int right,
+        int top,
+        int bottom,
+        string? autoDetected)
+    {
+        if (HasManualCrop(left, right, top, bottom))
+            return BuildManualCropFilter(left, right, top, bottom);
+
+        return mode switch
+        {
+            ShortSourceCropMode.None => "",
+            ShortSourceCropMode.Auto when !string.IsNullOrWhiteSpace(autoDetected) => autoDetected,
+            ShortSourceCropMode.Auto => CenterFourByThreeFilter,
+            _ => CenterFourByThreeFilter,
+        };
+    }
+
+    internal static string Prefix(string cropFilter, string nextFilter) =>
+        string.IsNullOrWhiteSpace(cropFilter) ? nextFilter : $"{cropFilter},{nextFilter}";
+
+    internal static List<string> BuildHorizontalCropDetectArguments(string inputFile, string start, double durationSeconds) =>
+    [
+        "-hide_banner",
+        "-ss",
+        string.IsNullOrWhiteSpace(start) ? "00:00:00" : start,
+        "-t",
+        durationSeconds.ToString("0.###", CultureInfo.InvariantCulture),
+        "-i",
+        inputFile,
+        "-an",
+        "-vf",
+        "crop=iw:trunc(ih*0.70/2)*2:0:trunc(ih*0.15/2)*2,cropdetect=limit=28:round=2:reset=0",
+        "-f",
+        "null",
+        "-",
+    ];
+
+    internal static string? SelectMostCommonCropSpec(string ffmpegOutput)
+    {
+        Dictionary<string, int> counts = new(StringComparer.Ordinal);
+        foreach (Match match in CropSpecRegex.Matches(ffmpegOutput))
+        {
+            string spec = match.Value;
+            counts[spec] = counts.GetValueOrDefault(spec) + 1;
+        }
+
+        return counts.Count == 0
+            ? null
+            : counts.OrderByDescending(pair => pair.Value).ThenBy(pair => pair.Key, StringComparer.Ordinal).First().Key;
+    }
+
+    internal static bool TryParseCropSpec(string spec, out int width, out int height, out int x, out int y)
+    {
+        Match match = CropSpecRegex.Match(spec);
+        if (!match.Success)
+        {
+            width = height = x = y = 0;
+            return false;
+        }
+
+        width = int.Parse(match.Groups[1].Value, CultureInfo.InvariantCulture);
+        height = int.Parse(match.Groups[2].Value, CultureInfo.InvariantCulture);
+        x = int.Parse(match.Groups[3].Value, CultureInfo.InvariantCulture);
+        y = int.Parse(match.Groups[4].Value, CultureInfo.InvariantCulture);
+        return true;
+    }
+
+    internal static bool TryBuildAutoHorizontalCrop(int detectedWidth, int detectedX, out int width, out int x)
+    {
+        int inset = (int)(detectedWidth * 0.005 / 2) * 2;
+        width = ((detectedWidth - (2 * inset)) / 2) * 2;
+        x = ((detectedX + inset) / 2) * 2;
+        if (width < 16)
+            return false;
+        return true;
+    }
+
+    internal static string? TryBuildAutoHorizontalFilter(string ffmpegOutput)
+    {
+        string? spec = SelectMostCommonCropSpec(ffmpegOutput);
+        if (spec is null || !TryParseCropSpec(spec, out int width, out _, out int x, out _))
+            return null;
+        if (!TryBuildAutoHorizontalCrop(width, x, out int cropWidth, out int cropX))
+            return null;
+
+        return $"crop={cropWidth}:ih:{cropX}:0";
+    }
+}

Services/SourceRecordingFinder.cs

@@ -0,0 +1,42 @@
+namespace AmiReel.Services;
+
+/// <summary>
+/// Locates sequential WinUAE-style recordings: output.avi, output_1.avi, output_2.avi, ...
+/// Stopping at the first missing name.
+/// </summary>
+public static class SourceRecordingFinder
+{
+    public const string BaseFileName = "output";
+    public const string FileExtension = ".avi";
+    public const int MaximumFiles = 500;
+
+    /// <summary>
+    /// Returns existing sequential recordings in <paramref name="folder"/>, or an empty
+    /// list when the folder is missing or <c>output.avi</c> is not present.
+    /// </summary>
+    public static IReadOnlyList<string> FindSequentialOutputs(string? folder)
+    {
+        if (string.IsNullOrWhiteSpace(folder) || !Directory.Exists(folder))
+            return [];
+
+        string directory = Path.GetFullPath(folder);
+        List<string> found = [];
+
+        string first = Path.Combine(directory, BaseFileName + FileExtension);
+        if (!File.Exists(first))
+            return found;
+
+        found.Add(first);
+
+        for (int index = 1; index < MaximumFiles; index++)
+        {
+            string next = Path.Combine(directory, $"{BaseFileName}_{index}{FileExtension}");
+            if (!File.Exists(next))
+                break;
+
+            found.Add(next);
+        }
+
+        return found;
+    }
+}