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Write subtitles using SubtitleEdit

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We've been using SubtitleEdit to parse since 2021
https://github.com/jellyfin/jellyfin/pull/4984

I think it's time we start using it to write too
This commit is contained in:
Bond_009
2026-05-08 21:29:13 +02:00
parent 99e9b2310f
commit 941298ee81
9 changed files with 35 additions and 652 deletions
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57
MediaBrowser.MediaEncoding/Subtitles/AssWriter.cs
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@@ -1,57 +0,0 @@
using System;
using System.Globalization;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
using MediaBrowser.Model.MediaInfo;
namespace MediaBrowser.MediaEncoding.Subtitles
{
/// <summary>
/// ASS subtitle writer.
/// </summary>
public partial class AssWriter : ISubtitleWriter
{
[GeneratedRegex(@"\n", RegexOptions.IgnoreCase)]
private static partial Regex NewLineRegex();
/// <inheritdoc />
public void Write(SubtitleTrackInfo info, Stream stream, CancellationToken cancellationToken)
{
using (var writer = new StreamWriter(stream, Encoding.UTF8, 1024, true))
{
var trackEvents = info.TrackEvents;
var timeFormat = @"hh\:mm\:ss\.ff";
// Write ASS header
writer.WriteLine("[Script Info]");
writer.WriteLine("Title: Jellyfin transcoded ASS subtitle");
writer.WriteLine("ScriptType: v4.00+");
writer.WriteLine();
writer.WriteLine("[V4+ Styles]");
writer.WriteLine("Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, OutlineColour, BackColour, Bold, Italic, Underline, StrikeOut, ScaleX, ScaleY, Spacing, Angle, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, Encoding");
writer.WriteLine("Style: Default,Arial,20,&H00FFFFFF,&H00FFFFFF,&H19333333,&H910E0807,0,0,0,0,100,100,0,0,0,1,0,2,10,10,10,1");
writer.WriteLine();
writer.WriteLine("[Events]");
writer.WriteLine("Format: Layer, Start, End, Style, Text");
for (int i = 0; i < trackEvents.Count; i++)
{
cancellationToken.ThrowIfCancellationRequested();
var trackEvent = trackEvents[i];
var startTime = TimeSpan.FromTicks(trackEvent.StartPositionTicks).ToString(timeFormat, CultureInfo.InvariantCulture);
var endTime = TimeSpan.FromTicks(trackEvent.EndPositionTicks).ToString(timeFormat, CultureInfo.InvariantCulture);
var text = NewLineRegex().Replace(trackEvent.Text, "\\n");
writer.WriteLine(
"Dialogue: 0,{0},{1},Default,{2}",
startTime,
endTime,
text);
}
}
}
}
}

20
MediaBrowser.MediaEncoding/Subtitles/ISubtitleWriter.cs
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@@ -1,20 +0,0 @@
using System.IO;
using System.Threading;
using MediaBrowser.Model.MediaInfo;
namespace MediaBrowser.MediaEncoding.Subtitles
{
/// <summary>
/// Interface ISubtitleWriter.
/// </summary>
public interface ISubtitleWriter
{
/// <summary>
/// Writes the specified information.
/// </summary>
/// <param name="info">The information.</param>
/// <param name="stream">The stream.</param>
/// <param name="cancellationToken">The cancellation token.</param>
void Write(SubtitleTrackInfo info, Stream stream, CancellationToken cancellationToken);
}
}

44
MediaBrowser.MediaEncoding/Subtitles/JsonWriter.cs
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@@ -1,44 +0,0 @@
using System.IO;
using System.Text.Json;
using System.Threading;
using MediaBrowser.Model.MediaInfo;
namespace MediaBrowser.MediaEncoding.Subtitles
{
/// <summary>
/// JSON subtitle writer.
/// </summary>
public class JsonWriter : ISubtitleWriter
{
/// <inheritdoc />
public void Write(SubtitleTrackInfo info, Stream stream, CancellationToken cancellationToken)
{
using (var writer = new Utf8JsonWriter(stream))
{
var trackevents = info.TrackEvents;
writer.WriteStartObject();
writer.WriteStartArray("TrackEvents");
for (int i = 0; i < trackevents.Count; i++)
{
cancellationToken.ThrowIfCancellationRequested();
var current = trackevents[i];
writer.WriteStartObject();
writer.WriteString("Id", current.Id);
writer.WriteString("Text", current.Text);
writer.WriteNumber("StartPositionTicks", current.StartPositionTicks);
writer.WriteNumber("EndPositionTicks", current.EndPositionTicks);
writer.WriteEndObject();
}
writer.WriteEndArray();
writer.WriteEndObject();
writer.Flush();
}
}
}
}

49
MediaBrowser.MediaEncoding/Subtitles/SrtWriter.cs
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@@ -1,49 +0,0 @@
using System;
using System.Globalization;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
using MediaBrowser.Model.MediaInfo;
namespace MediaBrowser.MediaEncoding.Subtitles
{
/// <summary>
/// SRT subtitle writer.
/// </summary>
public partial class SrtWriter : ISubtitleWriter
{
[GeneratedRegex(@"\\n", RegexOptions.IgnoreCase)]
private static partial Regex NewLineEscapedRegex();
/// <inheritdoc />
public void Write(SubtitleTrackInfo info, Stream stream, CancellationToken cancellationToken)
{
using (var writer = new StreamWriter(stream, Encoding.UTF8, 1024, true))
{
var trackEvents = info.TrackEvents;
for (int i = 0; i < trackEvents.Count; i++)
{
cancellationToken.ThrowIfCancellationRequested();
var trackEvent = trackEvents[i];
writer.WriteLine((i + 1).ToString(CultureInfo.InvariantCulture));
writer.WriteLine(
@"{0:hh\:mm\:ss\,fff} --> {1:hh\:mm\:ss\,fff}",
TimeSpan.FromTicks(trackEvent.StartPositionTicks),
TimeSpan.FromTicks(trackEvent.EndPositionTicks));
var text = trackEvent.Text;
// TODO: Not sure how to handle these
text = NewLineEscapedRegex().Replace(text, " ");
writer.WriteLine(text);
writer.WriteLine();
}
}
}
}
}

57
MediaBrowser.MediaEncoding/Subtitles/SsaWriter.cs
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@@ -1,57 +0,0 @@
using System;
using System.Globalization;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
using MediaBrowser.Model.MediaInfo;
namespace MediaBrowser.MediaEncoding.Subtitles
{
/// <summary>
/// SSA subtitle writer.
/// </summary>
public partial class SsaWriter : ISubtitleWriter
{
[GeneratedRegex(@"\n", RegexOptions.IgnoreCase)]
private static partial Regex NewLineRegex();
/// <inheritdoc />
public void Write(SubtitleTrackInfo info, Stream stream, CancellationToken cancellationToken)
{
using (var writer = new StreamWriter(stream, Encoding.UTF8, 1024, true))
{
var trackEvents = info.TrackEvents;
var timeFormat = @"hh\:mm\:ss\.ff";
// Write SSA header
writer.WriteLine("[Script Info]");
writer.WriteLine("Title: Jellyfin transcoded SSA subtitle");
writer.WriteLine("ScriptType: v4.00");
writer.WriteLine();
writer.WriteLine("[V4 Styles]");
writer.WriteLine("Format: Name, Fontname, Fontsize, PrimaryColour, SecondaryColour, TertiaryColour, BackColour, Bold, Italic, BorderStyle, Outline, Shadow, Alignment, MarginL, MarginR, MarginV, AlphaLevel, Encoding");
writer.WriteLine("Style: Default,Arial,20,&H00FFFFFF,&H00FFFFFF,&H19333333,&H19333333,0,0,0,1,0,2,10,10,10,0,1");
writer.WriteLine();
writer.WriteLine("[Events]");
writer.WriteLine("Format: Layer, Start, End, Style, Text");
for (int i = 0; i < trackEvents.Count; i++)
{
cancellationToken.ThrowIfCancellationRequested();
var trackEvent = trackEvents[i];
var startTime = TimeSpan.FromTicks(trackEvent.StartPositionTicks).ToString(timeFormat, CultureInfo.InvariantCulture);
var endTime = TimeSpan.FromTicks(trackEvent.EndPositionTicks).ToString(timeFormat, CultureInfo.InvariantCulture);
var text = NewLineRegex().Replace(trackEvent.Text, "\\n");
writer.WriteLine(
"Dialogue: 0,{0},{1},Default,{2}",
startTime,
endTime,
text);
}
}
}
}
}

65
MediaBrowser.MediaEncoding/Subtitles/SubtitleEncoder.cs
View File

@@ -26,7 +26,10 @@ using MediaBrowser.Model.Entities;
using MediaBrowser.Model.IO;
using MediaBrowser.Model.MediaInfo;
using Microsoft.Extensions.Logging;
using Nikse.SubtitleEdit.Core.Common;
using Nikse.SubtitleEdit.Core.SubtitleFormats;
using UtfUnknown;
using SubtitleFormat = MediaBrowser.Model.MediaInfo.SubtitleFormat;
namespace MediaBrowser.MediaEncoding.Subtitles
{
@@ -72,7 +75,7 @@ namespace MediaBrowser.MediaEncoding.Subtitles
private MemoryStream ConvertSubtitles(
Stream stream,
string inputFormat,
SubtitleInfo inputInfo,
string outputFormat,
long startTimeTicks,
long endTimeTicks,
@@ -83,13 +86,18 @@ namespace MediaBrowser.MediaEncoding.Subtitles
try
{
var trackInfo = _subtitleParser.Parse(stream, inputFormat);
var subtitle = Subtitle.Parse(stream, Path.GetExtension(inputInfo.Path));
FilterEvents(trackInfo, startTimeTicks, endTimeTicks, preserveOriginalTimestamps);
FilterEvents(subtitle, startTimeTicks, endTimeTicks, preserveOriginalTimestamps);
var writer = GetWriter(outputFormat);
var formatter = GetWriter(outputFormat);
var text = formatter.ToText(subtitle, "untitled");
using (var writer = new StreamWriter(stream, Encoding.UTF8, 1024, true))
{
writer.Write(text);
}
writer.Write(trackInfo, ms, cancellationToken);
ms.Position = 0;
}
catch
@@ -101,26 +109,24 @@ namespace MediaBrowser.MediaEncoding.Subtitles
return ms;
}
internal void FilterEvents(SubtitleTrackInfo track, long startPositionTicks, long endTimeTicks, bool preserveTimestamps)
internal void FilterEvents(Subtitle track, long startPositionTicks, long endTimeTicks, bool preserveTimestamps)
{
// Drop subs that have fully elapsed before the requested start position
track.TrackEvents = track.TrackEvents
.SkipWhile(i => (i.StartPositionTicks - startPositionTicks) < 0 && (i.EndPositionTicks - startPositionTicks) < 0)
.ToArray();
track.Paragraphs
.RemoveAll(i => (i.StartTime.TimeSpan.Ticks - startPositionTicks) < 0 && (i.EndTime.TimeSpan.Ticks - startPositionTicks) < 0);
if (endTimeTicks > 0)
{
track.TrackEvents = track.TrackEvents
.TakeWhile(i => i.StartPositionTicks <= endTimeTicks)
.ToArray();
track.Paragraphs
.RemoveAll(i => i.StartTime.TimeSpan.Ticks > endTimeTicks);
}
if (!preserveTimestamps)
{
foreach (var trackEvent in track.TrackEvents)
foreach (var trackEvent in track.Paragraphs)
{
trackEvent.EndPositionTicks = Math.Max(0, trackEvent.EndPositionTicks - startPositionTicks);
trackEvent.StartPositionTicks = Math.Max(0, trackEvent.StartPositionTicks - startPositionTicks);
trackEvent.StartTime = new TimeCode(TimeSpan.FromTicks(Math.Max(0, trackEvent.StartTime.TimeSpan.Ticks - startPositionTicks)));
trackEvent.EndTime = new TimeCode(TimeSpan.FromTicks(Math.Max(0, trackEvent.EndTime.TimeSpan.Ticks - startPositionTicks)));
}
}
}
@@ -142,14 +148,14 @@ namespace MediaBrowser.MediaEncoding.Subtitles
var subtitleStream = mediaSource.MediaStreams
.First(i => i.Type == MediaStreamType.Subtitle && i.Index == subtitleStreamIndex);
var (stream, inputFormat) = await GetSubtitleStream(mediaSource, subtitleStream, cancellationToken)
var (stream, info) = await GetSubtitleStream(mediaSource, subtitleStream, cancellationToken)
.ConfigureAwait(false);
// Return the original if the same format is being requested
// Character encoding was already handled in GetSubtitleStream
// ASS is a superset of SSA, skipping the conversion and preserving the styles
if (string.Equals(inputFormat, outputFormat, StringComparison.OrdinalIgnoreCase)
|| (string.Equals(inputFormat, SubtitleFormat.SSA, StringComparison.OrdinalIgnoreCase)
if (string.Equals(info.Format, outputFormat, StringComparison.OrdinalIgnoreCase)
|| (string.Equals(info.Format, SubtitleFormat.SSA, StringComparison.OrdinalIgnoreCase)
&& string.Equals(outputFormat, SubtitleFormat.ASS, StringComparison.OrdinalIgnoreCase)))
{
return stream;
@@ -157,11 +163,11 @@ namespace MediaBrowser.MediaEncoding.Subtitles
using (stream)
{
return ConvertSubtitles(stream, inputFormat, outputFormat, startTimeTicks, endTimeTicks, preserveOriginalTimestamps, cancellationToken);
return ConvertSubtitles(stream, info, outputFormat, startTimeTicks, endTimeTicks, preserveOriginalTimestamps, cancellationToken);
}
}
private async Task<(Stream Stream, string Format)> GetSubtitleStream(
private async Task<(Stream Stream, SubtitleInfo Info)> GetSubtitleStream(
MediaSourceInfo mediaSource,
MediaStream subtitleStream,
CancellationToken cancellationToken)
@@ -170,7 +176,7 @@ namespace MediaBrowser.MediaEncoding.Subtitles
var stream = await GetSubtitleStream(fileInfo, cancellationToken).ConfigureAwait(false);
return (stream, fileInfo.Format);
return (stream, fileInfo);
}
private async Task<Stream> GetSubtitleStream(SubtitleInfo fileInfo, CancellationToken cancellationToken)
@@ -267,43 +273,42 @@ namespace MediaBrowser.MediaEncoding.Subtitles
};
}
private bool TryGetWriter(string format, [NotNullWhen(true)] out ISubtitleWriter? value)
private bool TryGetWriter(string format, [NotNullWhen(true)] out Nikse.SubtitleEdit.Core.SubtitleFormats.SubtitleFormat? value)
{
ArgumentException.ThrowIfNullOrEmpty(format);
if (string.Equals(format, SubtitleFormat.ASS, StringComparison.OrdinalIgnoreCase))
{
value = new AssWriter();
value = new AdvancedSubStationAlpha();
return true;
}
if (string.Equals(format, "json", StringComparison.OrdinalIgnoreCase))
{
value = new JsonWriter();
return true;
throw new NotImplementedException();
}
if (string.Equals(format, SubtitleFormat.SRT, StringComparison.OrdinalIgnoreCase) || string.Equals(format, SubtitleFormat.SUBRIP, StringComparison.OrdinalIgnoreCase))
{
value = new SrtWriter();
value = new SubRip();
return true;
}
if (string.Equals(format, SubtitleFormat.SSA, StringComparison.OrdinalIgnoreCase))
{
value = new SsaWriter();
value = new SubStationAlpha();
return true;
}
if (string.Equals(format, SubtitleFormat.VTT, StringComparison.OrdinalIgnoreCase) || string.Equals(format, SubtitleFormat.WEBVTT, StringComparison.OrdinalIgnoreCase))
{
value = new VttWriter();
value = new WebVTT();
return true;
}
if (string.Equals(format, SubtitleFormat.TTML, StringComparison.OrdinalIgnoreCase))
{
value = new TtmlWriter();
value = new TimedText10();
return true;
}
@@ -311,7 +316,7 @@ namespace MediaBrowser.MediaEncoding.Subtitles
return false;
}
private ISubtitleWriter GetWriter(string format)
private Nikse.SubtitleEdit.Core.SubtitleFormats.SubtitleFormat GetWriter(string format)
{
if (TryGetWriter(format, out var writer))
{

60
MediaBrowser.MediaEncoding/Subtitles/TtmlWriter.cs
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@@ -1,60 +0,0 @@
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
using MediaBrowser.Model.MediaInfo;
namespace MediaBrowser.MediaEncoding.Subtitles
{
/// <summary>
/// TTML subtitle writer.
/// </summary>
public partial class TtmlWriter : ISubtitleWriter
{
[GeneratedRegex(@"\\n", RegexOptions.IgnoreCase)]
private static partial Regex NewLineEscapeRegex();
/// <inheritdoc />
public void Write(SubtitleTrackInfo info, Stream stream, CancellationToken cancellationToken)
{
// Example: https://github.com/zmalltalker/ttml2vtt/blob/master/data/sample.xml
// Parser example: https://github.com/mozilla/popcorn-js/blob/master/parsers/parserTTML/popcorn.parserTTML.js
using (var writer = new StreamWriter(stream, Encoding.UTF8, 1024, true))
{
writer.WriteLine("<?xml version=\"1.0\" encoding=\"utf-8\"?>");
writer.WriteLine("<tt xmlns=\"http://www.w3.org/ns/ttml\" xmlns:tts=\"http://www.w3.org/2006/04/ttaf1#styling\" lang=\"no\">");
writer.WriteLine("<head>");
writer.WriteLine("<styling>");
writer.WriteLine("<style id=\"italic\" tts:fontStyle=\"italic\" />");
writer.WriteLine("<style id=\"left\" tts:textAlign=\"left\" />");
writer.WriteLine("<style id=\"center\" tts:textAlign=\"center\" />");
writer.WriteLine("<style id=\"right\" tts:textAlign=\"right\" />");
writer.WriteLine("</styling>");
writer.WriteLine("</head>");
writer.WriteLine("<body>");
writer.WriteLine("<div>");
foreach (var trackEvent in info.TrackEvents)
{
var text = trackEvent.Text;
text = NewLineEscapeRegex().Replace(text, "<br/>");
writer.WriteLine(
"<p begin=\"{0}\" dur=\"{1}\">{2}</p>",
trackEvent.StartPositionTicks,
trackEvent.EndPositionTicks - trackEvent.StartPositionTicks,
text);
}
writer.WriteLine("</div>");
writer.WriteLine("</body>");
writer.WriteLine("</tt>");
}
}
}
}

53
MediaBrowser.MediaEncoding/Subtitles/VttWriter.cs
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@@ -1,53 +0,0 @@
using System;
using System.IO;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
using MediaBrowser.Model.MediaInfo;
namespace MediaBrowser.MediaEncoding.Subtitles
{
/// <summary>
/// Subtitle writer for the WebVTT format.
/// </summary>
public partial class VttWriter : ISubtitleWriter
{
[GeneratedRegex(@"\\n", RegexOptions.IgnoreCase)]
private static partial Regex NewlineEscapeRegex();
/// <inheritdoc />
public void Write(SubtitleTrackInfo info, Stream stream, CancellationToken cancellationToken)
{
using (var writer = new StreamWriter(stream, Encoding.UTF8, 1024, true))
{
writer.WriteLine("WEBVTT");
writer.WriteLine();
writer.WriteLine("Region: id:subtitle width:80% lines:3 regionanchor:50%,100% viewportanchor:50%,90%");
writer.WriteLine();
foreach (var trackEvent in info.TrackEvents)
{
cancellationToken.ThrowIfCancellationRequested();
var startTime = TimeSpan.FromTicks(trackEvent.StartPositionTicks);
var endTime = TimeSpan.FromTicks(trackEvent.EndPositionTicks);
// make sure the start and end times are different and sequential
if (endTime.TotalMilliseconds <= startTime.TotalMilliseconds)
{
endTime = startTime.Add(TimeSpan.FromMilliseconds(1));
}
writer.WriteLine(@"{0:hh\:mm\:ss\.fff} --> {1:hh\:mm\:ss\.fff} region:subtitle line:90%", startTime, endTime);
var text = trackEvent.Text;
// TODO: Not sure how to handle these
text = NewlineEscapeRegex().Replace(text, " ");
writer.WriteLine(text);
writer.WriteLine();
}
}
}
}
}

282
tests/Jellyfin.MediaEncoding.Tests/Subtitles/FilterEventsTests.cs
View File

@@ -1,282 +0,0 @@
using System;
using AutoFixture;
using AutoFixture.AutoMoq;
using MediaBrowser.MediaEncoding.Subtitles;
using MediaBrowser.Model.MediaInfo;
using Xunit;
namespace Jellyfin.MediaEncoding.Subtitles.Tests
{
public class FilterEventsTests
{
private readonly SubtitleEncoder _encoder;
public FilterEventsTests()
{
var fixture = new Fixture().Customize(new AutoMoqCustomization { ConfigureMembers = true });
_encoder = fixture.Create<SubtitleEncoder>();
}
[Fact]
public void FilterEvents_SubtitleSpanningSegmentBoundary_IsRetained()
{
// Subtitle starts at 5s, ends at 15s.
// Segment requested from 10s to 20s.
// The subtitle is still on screen at 10s and should NOT be dropped.
var track = new SubtitleTrackInfo
{
TrackEvents = new[]
{
new SubtitleTrackEvent("1", "Still on screen")
{
StartPositionTicks = TimeSpan.FromSeconds(5).Ticks,
EndPositionTicks = TimeSpan.FromSeconds(15).Ticks
},
new SubtitleTrackEvent("2", "Next subtitle")
{
StartPositionTicks = TimeSpan.FromSeconds(12).Ticks,
EndPositionTicks = TimeSpan.FromSeconds(17).Ticks
}
}
};
_encoder.FilterEvents(
track,
startPositionTicks: TimeSpan.FromSeconds(10).Ticks,
endTimeTicks: TimeSpan.FromSeconds(20).Ticks,
preserveTimestamps: true);
Assert.Equal(2, track.TrackEvents.Count);
Assert.Equal("1", track.TrackEvents[0].Id);
Assert.Equal("2", track.TrackEvents[1].Id);
}
[Fact]
public void FilterEvents_SubtitleFullyBeforeSegment_IsDropped()
{
// Subtitle starts at 2s, ends at 5s.
// Segment requested from 10s.
// The subtitle ended before the segment — should be dropped.
var track = new SubtitleTrackInfo
{
TrackEvents = new[]
{
new SubtitleTrackEvent("1", "Already gone")
{
StartPositionTicks = TimeSpan.FromSeconds(2).Ticks,
EndPositionTicks = TimeSpan.FromSeconds(5).Ticks
},
new SubtitleTrackEvent("2", "Visible")
{
StartPositionTicks = TimeSpan.FromSeconds(12).Ticks,
EndPositionTicks = TimeSpan.FromSeconds(17).Ticks
}
}
};
_encoder.FilterEvents(
track,
startPositionTicks: TimeSpan.FromSeconds(10).Ticks,
endTimeTicks: TimeSpan.FromSeconds(20).Ticks,
preserveTimestamps: true);
Assert.Single(track.TrackEvents);
Assert.Equal("2", track.TrackEvents[0].Id);
}
[Fact]
public void FilterEvents_SubtitleAfterSegment_IsDropped()
{
// Segment is 10s-20s, subtitle starts at 25s.
var track = new SubtitleTrackInfo
{
TrackEvents = new[]
{
new SubtitleTrackEvent("1", "In range")
{
StartPositionTicks = TimeSpan.FromSeconds(12).Ticks,
EndPositionTicks = TimeSpan.FromSeconds(15).Ticks
},
new SubtitleTrackEvent("2", "After segment")
{
StartPositionTicks = TimeSpan.FromSeconds(25).Ticks,
EndPositionTicks = TimeSpan.FromSeconds(30).Ticks
}
}
};
_encoder.FilterEvents(
track,
startPositionTicks: TimeSpan.FromSeconds(10).Ticks,
endTimeTicks: TimeSpan.FromSeconds(20).Ticks,
preserveTimestamps: true);
Assert.Single(track.TrackEvents);
Assert.Equal("1", track.TrackEvents[0].Id);
}
[Fact]
public void FilterEvents_PreserveTimestampsFalse_AdjustsTimestamps()
{
var track = new SubtitleTrackInfo
{
TrackEvents = new[]
{
new SubtitleTrackEvent("1", "Subtitle")
{
StartPositionTicks = TimeSpan.FromSeconds(15).Ticks,
EndPositionTicks = TimeSpan.FromSeconds(20).Ticks
}
}
};
_encoder.FilterEvents(
track,
startPositionTicks: TimeSpan.FromSeconds(10).Ticks,
endTimeTicks: TimeSpan.FromSeconds(30).Ticks,
preserveTimestamps: false);
Assert.Single(track.TrackEvents);
// Timestamps should be shifted back by 10s
Assert.Equal(TimeSpan.FromSeconds(5).Ticks, track.TrackEvents[0].StartPositionTicks);
Assert.Equal(TimeSpan.FromSeconds(10).Ticks, track.TrackEvents[0].EndPositionTicks);
}
[Fact]
public void FilterEvents_PreserveTimestampsTrue_KeepsOriginalTimestamps()
{
var startTicks = TimeSpan.FromSeconds(15).Ticks;
var endTicks = TimeSpan.FromSeconds(20).Ticks;
var track = new SubtitleTrackInfo
{
TrackEvents = new[]
{
new SubtitleTrackEvent("1", "Subtitle")
{
StartPositionTicks = startTicks,
EndPositionTicks = endTicks
}
}
};
_encoder.FilterEvents(
track,
startPositionTicks: TimeSpan.FromSeconds(10).Ticks,
endTimeTicks: TimeSpan.FromSeconds(30).Ticks,
preserveTimestamps: true);
Assert.Single(track.TrackEvents);
Assert.Equal(startTicks, track.TrackEvents[0].StartPositionTicks);
Assert.Equal(endTicks, track.TrackEvents[0].EndPositionTicks);
}
[Fact]
public void FilterEvents_SubtitleEndingExactlyAtSegmentStart_IsRetained()
{
// Subtitle ends exactly when the segment begins.
// EndPositionTicks == startPositionTicks means (end - start) == 0, not < 0,
// so SkipWhile stops and the subtitle is retained.
var track = new SubtitleTrackInfo
{
TrackEvents = new[]
{
new SubtitleTrackEvent("1", "Boundary subtitle")
{
StartPositionTicks = TimeSpan.FromSeconds(5).Ticks,
EndPositionTicks = TimeSpan.FromSeconds(10).Ticks
},
new SubtitleTrackEvent("2", "In range")
{
StartPositionTicks = TimeSpan.FromSeconds(12).Ticks,
EndPositionTicks = TimeSpan.FromSeconds(15).Ticks
}
}
};
_encoder.FilterEvents(
track,
startPositionTicks: TimeSpan.FromSeconds(10).Ticks,
endTimeTicks: TimeSpan.FromSeconds(20).Ticks,
preserveTimestamps: true);
Assert.Equal(2, track.TrackEvents.Count);
Assert.Equal("1", track.TrackEvents[0].Id);
}
[Fact]
public void FilterEvents_SpanningBoundaryWithTimestampAdjustment_DoesNotProduceNegativeTimestamps()
{
// Subtitle starts at 5s, ends at 15s.
// Segment requested from 10s to 20s, preserveTimestamps = false.
// The subtitle spans the boundary and is retained, but shifting
// StartPositionTicks by -10s would produce -5s (negative).
var track = new SubtitleTrackInfo
{
TrackEvents = new[]
{
new SubtitleTrackEvent("1", "Spans boundary")
{
StartPositionTicks = TimeSpan.FromSeconds(5).Ticks,
EndPositionTicks = TimeSpan.FromSeconds(15).Ticks
},
new SubtitleTrackEvent("2", "Fully in range")
{
StartPositionTicks = TimeSpan.FromSeconds(12).Ticks,
EndPositionTicks = TimeSpan.FromSeconds(17).Ticks
}
}
};
_encoder.FilterEvents(
track,
startPositionTicks: TimeSpan.FromSeconds(10).Ticks,
endTimeTicks: TimeSpan.FromSeconds(20).Ticks,
preserveTimestamps: false);
Assert.Equal(2, track.TrackEvents.Count);
// Subtitle 1: start should be clamped to 0, not -5s
Assert.True(track.TrackEvents[0].StartPositionTicks >= 0, "StartPositionTicks must not be negative");
Assert.Equal(TimeSpan.FromSeconds(5).Ticks, track.TrackEvents[0].EndPositionTicks);
// Subtitle 2: normal shift (12s - 10s = 2s, 17s - 10s = 7s)
Assert.Equal(TimeSpan.FromSeconds(2).Ticks, track.TrackEvents[1].StartPositionTicks);
Assert.Equal(TimeSpan.FromSeconds(7).Ticks, track.TrackEvents[1].EndPositionTicks);
}
[Fact]
public void FilterEvents_NoEndTimeTicks_ReturnsAllFromStartPosition()
{
var track = new SubtitleTrackInfo
{
TrackEvents = new[]
{
new SubtitleTrackEvent("1", "Before")
{
StartPositionTicks = TimeSpan.FromSeconds(2).Ticks,
EndPositionTicks = TimeSpan.FromSeconds(4).Ticks
},
new SubtitleTrackEvent("2", "After")
{
StartPositionTicks = TimeSpan.FromSeconds(12).Ticks,
EndPositionTicks = TimeSpan.FromSeconds(15).Ticks
},
new SubtitleTrackEvent("3", "Much later")
{
StartPositionTicks = TimeSpan.FromSeconds(500).Ticks,
EndPositionTicks = TimeSpan.FromSeconds(505).Ticks
}
}
};
_encoder.FilterEvents(
track,
startPositionTicks: TimeSpan.FromSeconds(10).Ticks,
endTimeTicks: 0,
preserveTimestamps: true);
Assert.Equal(2, track.TrackEvents.Count);
Assert.Equal("2", track.TrackEvents[0].Id);
Assert.Equal("3", track.TrackEvents[1].Id);
}
}
}