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Fix MPEG movie startup cadence

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This commit is contained in:
gamer147
2026-07-28 12:16:16 -04:00
parent ac2416e2d0
commit b7f67c8715
10 changed files with 269 additions and 34 deletions
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65
godot/FfmpegMovieDecoder.cs
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@@ -7,6 +7,7 @@ using Age.Engine.Sys4;
internal interface IMoviePacingClock
{
void StartPresentation() { }
bool WaitUntil(long elapsedMilliseconds, WaitHandle cancellation);
}
@@ -17,14 +18,22 @@ internal interface IExternallyAdvancedMoviePacingClock : IMoviePacingClock
internal sealed class StopwatchMoviePacingClock : IMoviePacingClock
{
private readonly long _startedAt = Stopwatch.GetTimestamp();
private long _startedAt;
public void StartPresentation()
{
long startedAt = Stopwatch.GetTimestamp();
Interlocked.CompareExchange(ref _startedAt, startedAt, 0);
}
public bool WaitUntil(long elapsedMilliseconds, WaitHandle cancellation)
{
StartPresentation();
while (true)
{
long startedAt = Interlocked.Read(ref _startedAt);
double remaining = elapsedMilliseconds
- Stopwatch.GetElapsedTime(_startedAt).TotalMilliseconds;
- Stopwatch.GetElapsedTime(startedAt).TotalMilliseconds;
if (remaining <= 0) return true;
int waitMilliseconds = (int)Math.Clamp(Math.Ceiling(remaining), 1, 1000);
if (cancellation.WaitOne(waitMilliseconds)) return false;
@@ -71,6 +80,7 @@ internal sealed class FfmpegMovieDecoder : IMovieDecoder
private readonly IFfmpegFrameSource _source;
private readonly IMoviePacingClock _clock;
private readonly ManualResetEvent _cancel = new(false);
private readonly ManualResetEvent _firstFramePresented = new(false);
private readonly Thread _thread;
private readonly Thread? _audioThread;
private readonly object _frameLock = new();
@@ -87,10 +97,20 @@ internal sealed class FfmpegMovieDecoder : IMovieDecoder
private int _queuedAudioFrames;
private int _activeWorkers;
private int _disposed;
private int _firstFrameTaken;
private long _firstFramePresentationTimeMs = -1;
public long? StopTimeMs => _source.Info.StopTimeMs;
public bool IsCompleted => _completed;
public string? Failure => Volatile.Read(ref _failure);
public long? FirstFramePresentationTimeMs
{
get
{
long value = Interlocked.Read(ref _firstFramePresentationTimeMs);
return value < 0 ? null : value;
}
}
public MovieAudioInfo? AudioInfo { get; }
public bool AudioDecodingCompleted => _audioDecodingCompleted;
@@ -134,6 +154,7 @@ internal sealed class FfmpegMovieDecoder : IMovieDecoder
if (_audioThread?.IsAlive == true) _audioThread.Join();
_source.Dispose();
_cancel.Dispose();
_firstFramePresented.Dispose();
_audioSpace.Dispose();
if (_clock is IDisposable disposableClock) disposableClock.Dispose();
throw;
@@ -151,8 +172,13 @@ internal sealed class FfmpegMovieDecoder : IMovieDecoder
}
frame = _latestFrame;
_latestFrame = null;
return true;
}
if (Interlocked.Exchange(ref _firstFrameTaken, 1) == 0)
{
_clock.StartPresentation();
_firstFramePresented.Set();
}
return true;
}
public bool TryTakeAudioChunk(out MovieAudioChunk chunk)
@@ -189,14 +215,17 @@ internal sealed class FfmpegMovieDecoder : IMovieDecoder
{
long lastTimestamp = -1;
long decodedFrames = 0;
long firstTimestamp = -1;
while (!_cancel.WaitOne(0))
{
if (!_source.TryDecodeNextVideoFrame(out var frame))
{
if (decodedFrames == 0)
throw new InvalidDataException("FFmpeg stream ended before producing a video frame");
long completionTime = Math.Max(_source.Info.StopTimeMs,
lastTimestamp + FrameIntervalMilliseconds(_source.Info));
long completionTime = PresentationDeadline(
Math.Max(_source.Info.StopTimeMs,
lastTimestamp + FrameIntervalMilliseconds(_source.Info)),
firstTimestamp);
if (_clock.WaitUntil(completionTime, _cancel))
{
_videoTimelineCompleted = true;
@@ -207,7 +236,20 @@ internal sealed class FfmpegMovieDecoder : IMovieDecoder
if (frame.PresentationTimeMs < 0 || frame.PresentationTimeMs < lastTimestamp)
throw new InvalidDataException(
$"FFmpeg returned non-monotonic video timestamp {frame.PresentationTimeMs} after {lastTimestamp}");
if (!_clock.WaitUntil(frame.PresentationTimeMs, _cancel)) return;
if (decodedFrames == 0)
{
firstTimestamp = frame.PresentationTimeMs;
Interlocked.Exchange(ref _firstFramePresentationTimeMs, firstTimestamp);
lock (_frameLock) _latestFrame = frame.Image;
lastTimestamp = frame.PresentationTimeMs;
decodedFrames++;
int signalled = WaitHandle.WaitAny([_cancel, _firstFramePresented]);
if (signalled == 0) return;
continue;
}
if (!_clock.WaitUntil(PresentationDeadline(frame.PresentationTimeMs, firstTimestamp),
_cancel))
return;
lock (_frameLock) _latestFrame = frame.Image;
lastTimestamp = frame.PresentationTimeMs;
decodedFrames++;
@@ -295,16 +337,27 @@ internal sealed class FfmpegMovieDecoder : IMovieDecoder
return Math.Max(1, scaledDenominator / info.FrameRateNumerator);
}
private long PresentationDeadline(long sourceTimestamp, long firstVideoTimestamp)
{
// MPEG program streams may put the first video sample hundreds of milliseconds after the audio
// stream's mux timestamp origin. DirectShow presents the video's first sample as video time zero;
// retaining the absolute mux offset here would freeze that sample until the audio clock caught up.
// Preserve every decoded frame and its cadence, but rebase the video stream to its first sample.
return Math.Max(0, sourceTimestamp - firstVideoTimestamp);
}
public void Dispose()
{
if (Interlocked.Exchange(ref _disposed, 1) != 0) return;
_cancel.Set();
_firstFramePresented.Set();
_audioSpace.Set();
if (_thread.IsAlive && Thread.CurrentThread != _thread)
_thread.Join();
if (_audioThread?.IsAlive == true && Thread.CurrentThread != _audioThread)
_audioThread.Join();
_cancel.Dispose();
_firstFramePresented.Dispose();
_audioSpace.Dispose();
if (_clock is IDisposable disposableClock) disposableClock.Dispose();
}