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Show MKV progress window for multi-track files (#12193) #12197

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Merged
niksedk merged 1 commit into from
Jul 5, 2026
+148 −51
Merged

Show MKV progress window for multi-track files (#12193) #12197

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199 changes: 148 additions & 51 deletions src/ui/Features/Shared/PickMatroskaTrack/PickMatroskaTrackViewModel.cs
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
using Nikse.SubtitleEdit.UiLogic.Export;
using Avalonia.Controls;
using Avalonia.Input;
using Avalonia.Media.Imaging;
using Avalonia.Threading;
using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
Expand All @@ -19,6 +20,7 @@
using System.Collections.ObjectModel;
using System.IO;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace Nikse.SubtitleEdit.Features.Shared.PickMatroskaTrack;
Expand All @@ -43,6 +45,18 @@ public partial class PickMatroskaTrackViewModel : ObservableObject
private MatroskaFile? _matroskaFile;
private string _fileName;

// MatroskaFile is not thread-safe (single shared FileStream), so preview parsing must be
// serialized. The token lets a newer selection discard a stale preview still queued behind it.
private readonly SemaphoreSlim _previewLock = new(1, 1);
private int _trackChangeToken;

// GetSubtitle reads (and caches) the whole cluster data on its first call; that is the only
// slow part, so the progress window is only shown until that initial read has completed.
private bool _clusterLoaded;

// Only bother with the progress window for files large enough that the read is noticeable.
private const long MatroskaProgressWindowMinFileSize = 25 * 1024 * 1024; // 25 MB

public PickMatroskaTrackViewModel(IFileHelper fileHelper, IWindowService windowService)
{
_fileHelper = fileHelper;
Expand Down Expand Up @@ -212,100 +226,183 @@ internal void OnKeyDownHandler(object? sender, KeyEventArgs e)

internal void DataGridTracksSelectionChanged(object? sender, SelectionChangedEventArgs e)
{
TrackChanged();
_ = TrackChangedAsync();
}

private bool TrackChanged()
/// <summary>
/// Builds the preview for the selected track. The actual parsing (which, on the first call,
/// reads the whole file's cluster data) runs off the UI thread with a progress window so the
/// dialog no longer freezes when picking a track in a large multi-subtitle file (#12193).
/// </summary>
private async Task TrackChangedAsync()
{
var selectedTrack = SelectedTrack;
if (selectedTrack == null || selectedTrack.MatroskaTrackInfo == null)
var trackInfo = SelectedTrack?.MatroskaTrackInfo;
var matroskaFile = _matroskaFile;
var token = ++_trackChangeToken;

Rows.Clear();
if (trackInfo == null || matroskaFile == null)
{
SubtitleCountText = string.Empty;
return false;
return;
}

Rows.Clear();
var count = 0;
var trackInfo = selectedTrack.MatroskaTrackInfo!;
var subtitles = _matroskaFile?.GetSubtitle(trackInfo.TrackNumber, null);
if (trackInfo.CodecId == MatroskaTrackType.SubRip && subtitles != null)
await _previewLock.WaitAsync();
try
{
count = AddTextContent(trackInfo, subtitles, new SubRip());
// A newer selection arrived while we were waiting for the previous preview to finish;
// let that newer call build the preview instead.
if (token != _trackChangeToken)
{
return;
}

PleaseWaitViewModel? pleaseWaitVm = null;
if (!_clusterLoaded)
{
long fileSize = 0;
try
{
fileSize = new FileInfo(matroskaFile.Path).Length;
}
catch
{
// ignore - just means no size-based gating
}

if (fileSize >= MatroskaProgressWindowMinFileSize && Window != null)
{
pleaseWaitVm = _windowService.ShowWindow<PleaseWaitWindow, PleaseWaitViewModel>(Window);
pleaseWaitVm.StatusText = Se.Language.Main.ParsingMatroskaFile;
}
}

try
{
var vm = pleaseWaitVm;
var preview = await Task.Run(() => BuildPreview(trackInfo, matroskaFile, vm));
_clusterLoaded = true;

// Discard the result if the user moved on to another track meanwhile.
if (token != _trackChangeToken)
{
return;
}

foreach (var cue in preview.Cues)
{
Rows.Add(new MatroskaSubtitleCueDisplay
{
Number = cue.Number,
Show = cue.Show,
Duration = cue.Duration,
Text = cue.Text ?? string.Empty,
Image = cue.Image != null ? new Image { Source = cue.Image } : null,
});
}

SubtitleCountText = string.Format(Se.Language.File.Import.NumberOfSubtitlesX, preview.Count);
}
catch (Exception exception)
{
Se.LogError(exception, "Error building Matroska track preview");
SubtitleCountText = string.Empty;
}
finally
{
pleaseWaitVm?.Close();
}
}
else if (trackInfo.CodecId is MatroskaTrackType.SubStationAlpha or MatroskaTrackType.SubStationAlpha2 && subtitles != null)
finally
{
count = AddTextContent(trackInfo, subtitles, new SubStationAlpha());
_previewLock.Release();
}
else if (trackInfo.CodecId is MatroskaTrackType.AdvancedSubStationAlpha or MatroskaTrackType.AdvancedSubStationAlpha2 && subtitles != null)
}

/// <summary>
/// Parses the selected track into plain preview data. Runs on a background thread, so it must
/// not touch any UI controls - the Avalonia <see cref="Bitmap"/> objects it creates are decoded
/// here, but the <see cref="Image"/> controls that host them are built on the UI thread.
/// </summary>
private static PreviewResult BuildPreview(MatroskaTrackInfo trackInfo, MatroskaFile matroskaFile, PleaseWaitViewModel? pleaseWaitVm)
{
var cues = new List<PreviewCueData>();
var count = 0;

MatroskaFile.LoadMatroskaCallback? callback =
pleaseWaitVm != null ? (position, total) => pleaseWaitVm.ReportProgress(position, total) : null;
var subtitles = matroskaFile.GetSubtitle(trackInfo.TrackNumber, callback);
if (subtitles == null)
{
count = AddTextContent(trackInfo, subtitles, new AdvancedSubStationAlpha());
return new PreviewResult(0, cues);
}
else if (trackInfo.CodecId is MatroskaTrackType.WebVTT or MatroskaTrackType.WebVTT2 && subtitles != null)

if (trackInfo.CodecId is MatroskaTrackType.SubRip
or MatroskaTrackType.SubStationAlpha or MatroskaTrackType.SubStationAlpha2
or MatroskaTrackType.AdvancedSubStationAlpha or MatroskaTrackType.AdvancedSubStationAlpha2
or MatroskaTrackType.WebVTT or MatroskaTrackType.WebVTT2)
{
count = AddTextContent(trackInfo, subtitles, new WebVTT());
var sub = new Subtitle();
Utilities.LoadMatroskaTextSubtitle(trackInfo, matroskaFile, subtitles, sub);
count = sub.Paragraphs.Count;
foreach (var p in sub.Paragraphs)
{
cues.Add(new PreviewCueData
{
Number = p.Number,
Text = p.Text,
Show = TimeSpan.FromMilliseconds(p.StartTime.TotalMilliseconds),
Duration = TimeSpan.FromMilliseconds(p.EndTime.TotalMilliseconds - p.StartTime.TotalMilliseconds),
});
}
}
else if (trackInfo.CodecId == MatroskaTrackType.BluRay && subtitles != null && _matroskaFile != null)
else if (trackInfo.CodecId == MatroskaTrackType.BluRay)
{
var pcsData = BluRaySupParser.ParseBluRaySupFromMatroska(trackInfo, _matroskaFile);
var pcsData = BluRaySupParser.ParseBluRaySupFromMatroska(trackInfo, matroskaFile);
count = pcsData.Count;
for (var i = 0; i < 20 && i < pcsData.Count; i++)
{
var item = pcsData[i];
var bitmap = item.GetBitmap();
var cue = new MatroskaSubtitleCueDisplay()
cues.Add(new PreviewCueData
{
Number = i + 1,
Show = TimeSpan.FromMilliseconds(item.StartTimeCode.TotalMilliseconds),
Duration = TimeSpan.FromMilliseconds(item.EndTimeCode.TotalMilliseconds - item.StartTimeCode.TotalMilliseconds),
Image = new Image { Source = bitmap.ToAvaloniaBitmap() },
};
Rows.Add(cue);
Image = item.GetBitmap().ToAvaloniaBitmap(),
});
}
}
else if (trackInfo.CodecId == MatroskaTrackType.TextSt && subtitles != null && _matroskaFile != null)
else if (trackInfo.CodecId == MatroskaTrackType.TextSt)
{
var subtitle = new Subtitle();
Utilities.LoadMatroskaTextSubtitle(trackInfo, _matroskaFile, subtitles, subtitle);
Utilities.LoadMatroskaTextSubtitle(trackInfo, matroskaFile, subtitles, subtitle);
Utilities.ParseMatroskaTextSt(trackInfo, subtitles, subtitle);

count = subtitle.Paragraphs.Count;
for (var i = 0; i < 20 && i < subtitle.Paragraphs.Count; i++)
{
var item = subtitle.Paragraphs[i];
var cue = new MatroskaSubtitleCueDisplay()
cues.Add(new PreviewCueData
{
Number = i + 1,
Show = item.StartTime.TimeSpan,
Duration = TimeSpan.FromMilliseconds(item.EndTime.TotalMilliseconds - item.StartTime.TotalMilliseconds),
Text = item.Text,
};
Rows.Add(cue);
});
}
}

SubtitleCountText = string.Format(Se.Language.File.Import.NumberOfSubtitlesX, count);
return true;
return new PreviewResult(count, cues);
}

private int AddTextContent(MatroskaTrackInfo trackInfo, List<MatroskaSubtitle> subtitles, SubtitleFormat format)
{
var sub = new Subtitle();
Utilities.LoadMatroskaTextSubtitle(trackInfo, _matroskaFile, subtitles, sub);
var raw = format.ToText(sub, string.Empty);
for (var i = 0; i < sub.Paragraphs.Count; i++)
{
var p = sub.Paragraphs[i];
var cue = new MatroskaSubtitleCueDisplay()
{
Number = p.Number,
Text = p.Text,
Show = TimeSpan.FromMilliseconds(p.StartTime.TotalMilliseconds),
Duration = TimeSpan.FromMilliseconds(p.EndTime.TotalMilliseconds - p.StartTime.TotalMilliseconds),
};
Rows.Add(cue);
}
private sealed record PreviewResult(int Count, List<PreviewCueData> Cues);

return sub.Paragraphs.Count;
private sealed class PreviewCueData
{
public int Number { get; init; }
public TimeSpan Show { get; init; }
public TimeSpan Duration { get; init; }
public string? Text { get; init; }
public Bitmap? Image { get; init; }
}

internal void SelectAndScrollToRow(int index)
Expand All @@ -319,7 +416,7 @@ internal void SelectAndScrollToRow(int index)
{
TracksGrid.SelectedIndex = index;
TracksGrid.ScrollIntoView(TracksGrid.SelectedItem, null);
TrackChanged();
_ = TrackChangedAsync();
}, DispatcherPriority.Background);
}
}