Files
OpenMaidEngine/engine/Age.Engine.Frontend/FfmpegMovieDecoder.cs
2026-08-03 11:33:38 -04:00

472 lines
17 KiB
C#

using System;
using System.Diagnostics;
using System.IO;
using System.Collections.Generic;
using System.Threading;
using Age.Engine.Model;
using Age.Engine.Sys4;
internal interface IMoviePacingClock
{
void StartPresentation() { }
bool WaitUntil(long elapsedMilliseconds, WaitHandle cancellation);
}
internal interface IExternallyAdvancedMoviePacingClock : IMoviePacingClock
{
void AdvanceTo(long elapsedMilliseconds);
}
internal sealed class StopwatchMoviePacingClock : IMoviePacingClock
{
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;
if (remaining <= 0) return true;
int waitMilliseconds = (int)Math.Clamp(Math.Ceiling(remaining), 1, 1000);
if (cancellation.WaitOne(waitMilliseconds)) return false;
}
}
}
internal sealed class ExternallyAdvancedMoviePacingClock : IExternallyAdvancedMoviePacingClock, IDisposable
{
private readonly AutoResetEvent _advanced = new(false);
private long _now;
public bool WaitUntil(long elapsedMilliseconds, WaitHandle cancellation)
{
while (Interlocked.Read(ref _now) < elapsedMilliseconds)
{
int signalled = WaitHandle.WaitAny([cancellation, _advanced]);
if (signalled == 0) return false;
}
return true;
}
public void AdvanceTo(long elapsedMilliseconds)
{
long current;
do
{
current = Interlocked.Read(ref _now);
if (elapsedMilliseconds <= current) return;
}
while (Interlocked.CompareExchange(ref _now, elapsedMilliseconds, current) != current);
_advanced.Set();
}
public void Dispose() => _advanced.Dispose();
}
/// <summary>
/// Timestamp-paced FFmpeg delivery. Video-only streams retain monotonic stopwatch pacing. Audio-bearing
/// streams decode PCM into a bounded queue and advance video against the sound-device clock supplied by Godot.
/// </summary>
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();
private readonly object _audioLock = new();
private readonly Queue<MovieAudioChunk> _audioChunks = new();
private readonly AutoResetEvent _audioSpace = new(false);
private readonly int _maximumQueuedAudioFrames;
private readonly long _initialPositionMs;
private readonly long? _presentationDurationMs;
private RgbaImage? _latestFrame;
private volatile bool _completed;
private volatile bool _videoTimelineCompleted;
private volatile bool _audioDecodingCompleted;
private volatile bool _audioSubmitted;
private string? _failure;
private int _queuedAudioFrames;
private int _activeWorkers;
private int _disposed;
private int _firstFrameTaken;
private long _firstFramePresentationTimeMs = -1;
public long? StopTimeMs => _source.Info.StopTimeMs;
public long InitialPositionMs => _initialPositionMs;
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;
public FfmpegMovieDecoder(
MoviePayload movie, long initialPositionMs = 0, long? presentationDurationMs = null)
: this(new FfmpegMovieSession(movie), null, initialPositionMs, presentationDurationMs) { }
internal FfmpegMovieDecoder(IFfmpegFrameSource source, IMoviePacingClock? clock,
long initialPositionMs = 0, long? presentationDurationMs = null)
{
_source = source ?? throw new ArgumentNullException(nameof(source));
_initialPositionMs = Math.Clamp(
initialPositionMs,
0,
Math.Max(0, source.Info.StopTimeMs - 1));
_presentationDurationMs = presentationDurationMs is >= 0
? Math.Max(0, presentationDurationMs.Value)
: null;
try
{
if (_initialPositionMs > 0)
source.Seek(_initialPositionMs);
}
catch
{
source.Dispose();
throw;
}
_clock = clock ?? (source.Info.HasAudio
? new ExternallyAdvancedMoviePacingClock()
: new StopwatchMoviePacingClock());
if (source.Info.HasAudio)
{
AudioInfo = new MovieAudioInfo(source.Info.AudioSampleRate, source.Info.AudioChannels);
_maximumQueuedAudioFrames = Math.Max(source.Info.AudioSampleRate / 2,
source.Info.AudioFrameSamples * 2);
}
_thread = new Thread(DecodeThread)
{
IsBackground = true,
Name = "AGE FFmpeg movie video",
};
_audioThread = source.Info.HasAudio
? new Thread(AudioDecodeThread)
{
IsBackground = true,
Name = "AGE FFmpeg movie audio",
}
: null;
_activeWorkers = _audioThread == null ? 1 : 2;
try
{
_thread.Start();
_audioThread?.Start();
}
catch
{
_cancel.Set();
if (_thread.IsAlive) _thread.Join();
if (_audioThread?.IsAlive == true) _audioThread.Join();
_source.Dispose();
_cancel.Dispose();
_firstFramePresented.Dispose();
_audioSpace.Dispose();
if (_clock is IDisposable disposableClock) disposableClock.Dispose();
throw;
}
}
public bool TryTakeFrame(out RgbaImage frame)
{
lock (_frameLock)
{
if (_latestFrame == null)
{
frame = default!;
return false;
}
frame = _latestFrame;
_latestFrame = null;
}
if (Interlocked.Exchange(ref _firstFrameTaken, 1) == 0)
{
_clock.StartPresentation();
_firstFramePresented.Set();
}
return true;
}
public bool TryTakeAudioChunk(out MovieAudioChunk chunk)
{
lock (_audioLock)
{
if (_audioChunks.Count == 0)
{
chunk = default!;
return false;
}
chunk = _audioChunks.Dequeue();
_queuedAudioFrames -= chunk.FrameCount;
}
_audioSpace.Set();
return true;
}
public void AdvancePlaybackClock(long elapsedMilliseconds)
{
if (_clock is IExternallyAdvancedMoviePacingClock external)
external.AdvanceTo(Math.Max(0, elapsedMilliseconds));
}
public void MarkAudioSubmitted()
{
_audioSubmitted = true;
UpdateCompletion();
}
private void DecodeThread()
{
try
{
long lastTimestamp = -1;
long decodedFrames = 0;
long firstTimestamp = -1;
FfmpegVideoFrame? selectedSeekFrame = null;
FfmpegVideoFrame? pendingAfterSeek = null;
if (_initialPositionMs > 0)
selectedSeekFrame = SelectFrameAtInitialPosition(out pendingAfterSeek);
while (!_cancel.WaitOne(0))
{
FfmpegVideoFrame frame;
if (selectedSeekFrame != null)
{
frame = selectedSeekFrame;
selectedSeekFrame = null;
}
else if (pendingAfterSeek != null)
{
frame = pendingAfterSeek;
pendingAfterSeek = null;
}
else if (!_source.TryDecodeNextVideoFrame(out frame))
{
if (decodedFrames == 0)
throw new InvalidDataException("FFmpeg stream ended before producing a video frame");
long completionTime = _presentationDurationMs
?? PresentationDeadline(
Math.Max(_source.Info.StopTimeMs,
lastTimestamp + FrameIntervalMilliseconds(_source.Info)),
firstTimestamp);
if (_clock.WaitUntil(completionTime, _cancel))
{
_videoTimelineCompleted = true;
UpdateCompletion();
}
return;
}
if (frame.PresentationTimeMs < 0 || frame.PresentationTimeMs < lastTimestamp)
throw new InvalidDataException(
$"FFmpeg returned non-monotonic video timestamp {frame.PresentationTimeMs} after {lastTimestamp}");
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++;
}
}
catch (Exception error)
{
Fail(error);
}
finally
{
WorkerCompleted();
}
}
private FfmpegVideoFrame? SelectFrameAtInitialPosition(out FfmpegVideoFrame? pending)
{
pending = null;
FfmpegVideoFrame? candidate = null;
long priorTimestamp = -1;
while (!_cancel.WaitOne(0) && _source.TryDecodeNextVideoFrame(out FfmpegVideoFrame frame))
{
if (frame.PresentationTimeMs < 0 || frame.PresentationTimeMs < priorTimestamp)
throw new InvalidDataException(
$"FFmpeg returned non-monotonic video timestamp {frame.PresentationTimeMs} " +
$"after {priorTimestamp} during seek preroll");
priorTimestamp = frame.PresentationTimeMs;
if (frame.PresentationTimeMs <= _initialPositionMs)
{
candidate = frame;
continue;
}
if (candidate == null)
return frame;
pending = frame;
return candidate;
}
return candidate;
}
private void AudioDecodeThread()
{
try
{
long priorSourceTimestamp = -1;
long priorRebasedTimestamp = -1;
while (!_cancel.WaitOne(0))
{
while (Volatile.Read(ref _queuedAudioFrames) >= _maximumQueuedAudioFrames)
{
int signalled = WaitHandle.WaitAny([_cancel, _audioSpace]);
if (signalled == 0) return;
}
if (!_source.TryDecodeNextAudioChunk(out FfmpegAudioChunk decoded))
{
_audioDecodingCompleted = true;
UpdateCompletion();
return;
}
if (decoded.FrameCount <= 0
|| decoded.InterleavedStereo.Length != checked(decoded.FrameCount * 2)
|| decoded.PresentationTimeMs < 0
|| decoded.PresentationTimeMs < priorSourceTimestamp)
throw new InvalidDataException(
$"FFmpeg returned invalid audio block {decoded.FrameCount}f " +
$"at {decoded.PresentationTimeMs} ms after {priorSourceTimestamp} ms");
priorSourceTimestamp = decoded.PresentationTimeMs;
MovieAudioChunk? chunk = RebaseAudioChunk(decoded);
if (chunk == null) continue;
if (chunk.PresentationTimeMs < priorRebasedTimestamp)
throw new InvalidDataException(
$"FFmpeg seek produced non-monotonic rebased audio timestamp " +
$"{chunk.PresentationTimeMs} after {priorRebasedTimestamp} ms");
lock (_audioLock)
{
_audioChunks.Enqueue(chunk);
_queuedAudioFrames += chunk.FrameCount;
}
priorRebasedTimestamp = chunk.PresentationTimeMs;
}
}
catch (Exception error)
{
Fail(error);
}
finally
{
WorkerCompleted();
}
}
private MovieAudioChunk? RebaseAudioChunk(FfmpegAudioChunk decoded)
{
int trimFrames = 0;
if (_initialPositionMs > decoded.PresentationTimeMs)
{
long deltaMs = _initialPositionMs - decoded.PresentationTimeMs;
long required = checked(
(deltaMs * (long)_source.Info.AudioSampleRate + 999) / 1000);
trimFrames = checked((int)Math.Min(decoded.FrameCount, required));
}
if (trimFrames >= decoded.FrameCount) return null;
float[] samples = decoded.InterleavedStereo;
int frameCount = decoded.FrameCount - trimFrames;
if (trimFrames > 0)
{
var trimmed = new float[checked(frameCount * 2)];
Array.Copy(samples, checked(trimFrames * 2), trimmed, 0, trimmed.Length);
samples = trimmed;
}
long trimmedTimestamp = decoded.PresentationTimeMs
+ trimFrames * 1000L / _source.Info.AudioSampleRate;
long rebasedTimestamp = Math.Max(0, trimmedTimestamp - _initialPositionMs);
return new MovieAudioChunk(samples, frameCount, rebasedTimestamp);
}
private void Fail(Exception error)
{
Interlocked.CompareExchange(ref _failure, error.Message, null);
_completed = true; // decode failure must never strand an AGE movie wait
_cancel.Set();
_audioSpace.Set();
}
private void UpdateCompletion()
{
if (_failure != null || !_videoTimelineCompleted) return;
if (AudioInfo != null && (!_audioDecodingCompleted || !_audioSubmitted)) return;
_completed = true;
}
private void WorkerCompleted()
{
if (Interlocked.Decrement(ref _activeWorkers) == 0) _source.Dispose();
}
private static long FrameIntervalMilliseconds(FfmpegMovieInfo info)
{
if (info.FrameRateNumerator <= 0 || info.FrameRateDenominator <= 0) return 0;
long scaledDenominator = checked((long)info.FrameRateDenominator * 1000);
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.
long sourceElapsed = Math.Max(0, sourceTimestamp - firstVideoTimestamp);
if (_presentationDurationMs is not { } duration
|| _source.Info.StopTimeMs <= 0)
return sourceElapsed;
return checked(sourceElapsed * duration / _source.Info.StopTimeMs);
}
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();
}
}
internal sealed class FfmpegMovieDecoderFactory : IMovieDecoderFactory
{
public IMovieDecoder Open(
MoviePayload movie, long initialPositionMs = 0, long? presentationDurationMs = null)
=> new FfmpegMovieDecoder(movie, initialPositionMs, presentationDurationMs);
}