Implement decoder draining - fixes an issue where last frames were dr…

…opped (closes #72)

FFMediaToolkit/Common/Internal/MediaPacket.cs

@@ -56,6 +56,20 @@ public static MediaPacket AllocateEmpty()
  return new MediaPacket(packet);
  }
 
+ /// <summary>
+ /// Creates a flush packet.
+ /// </summary>
+ /// <param name="streamIndex">The stream index.</param>
+ /// <returns>The flush packet.</returns>
+ public static MediaPacket CreateFlushPacket(int streamIndex)
+ {
+ var packet = ffmpeg.av_packet_alloc();
+ packet->stream_index = streamIndex;
+ packet->data = null;
+ packet->size = 0;
+ return new MediaPacket(packet);
+ }
+
  /// <summary>
  /// Sets valid PTS/DTS values. Used only in encoding.
  /// </summary>

FFMediaToolkit/Decoding/Internal/Decoder.cs

@@ -2,6 +2,7 @@
 {
  using System;
  using System.Collections.Generic;
+ using System.IO;
  using FFMediaToolkit.Common;
  using FFMediaToolkit.Common.Internal;
  using FFMediaToolkit.Helpers;
@@ -15,6 +16,7 @@ internal unsafe class Decoder : Wrapper<AVCodecContext>
  private readonly int bufferLimit;
  private int bufferSize = 0;
  private bool reuseLastPacket;
+ private bool flushing = false;
  private MediaPacket packet;
 
  /// <summary>
@@ -114,6 +116,8 @@ public void SkipFrames(long targetTs)
  /// </summary>
  public void DiscardBufferedData()
  {
+ ffmpeg.avcodec_flush_buffers(Pointer);
+
  foreach (var packet in BufferedPackets)
  {
  packet.Wipe();
@@ -122,18 +126,13 @@ public void DiscardBufferedData()
 
  BufferedPackets.Clear();
  bufferSize = 0;
+ flushing = false;
  }
 
- /// <summary>
- /// Flushes the codec buffers.
- /// </summary>
- public void FlushUnmanagedBuffers() => ffmpeg.avcodec_flush_buffers(Pointer);
-
  /// <inheritdoc/>
  protected override void OnDisposing()
  {
  RecentlyDecodedFrame.Dispose();
- FlushUnmanagedBuffers();
  ffmpeg.avcodec_close(Pointer);
  }
 
@@ -144,10 +143,20 @@ private void ReadNextFrame()
 
  do
  {
- DecodePacket(); // Gets the next packet and sends it to the decoder
+ if (!flushing)
+ {
+ DecodePacket(); // Gets the next packet and sends it to the decoder
+ }
+
  error = ffmpeg.avcodec_receive_frame(Pointer, RecentlyDecodedFrame.Pointer); // Tries to decode frame from the packets.
  }
  while (error == ffmpeg.AVERROR(ffmpeg.EAGAIN) || error == -35); // The EAGAIN code means that the frame decoding has not been completed and more packets are needed.
+
+ if (error == ffmpeg.AVERROR_EOF)
+ {
+ throw new EndOfStreamException("End of file.");
+ }
+
  error.ThrowIfError("An error occurred while decoding the frame.");
  }
 
@@ -156,23 +165,24 @@ private void DecodePacket()
  if (!reuseLastPacket)
  {
  if (IsBufferEmpty)
- OwnerFile.GetPacketFromStream(Info.Index);
+ {
+ flushing = !OwnerFile.GetPacketFromStream(Info.Index);
+ }
+
  packet = BufferedPackets.Dequeue();
  bufferSize -= packet.Pointer->size;
  }
 
  // Sends the packet to the decoder.
  var result = ffmpeg.avcodec_send_packet(Pointer, packet);
 
- if (result == ffmpeg.AVERROR(ffmpeg.EAGAIN))
- {
- reuseLastPacket = true;
- }
- else
+ reuseLastPacket = result == ffmpeg.AVERROR(ffmpeg.EAGAIN);
+
+ if (!reuseLastPacket)
  {
- reuseLastPacket = false;
- result.ThrowIfError("Cannot send a packet to the decoder.");
  packet.Wipe();
+ packet.Dispose();
+ result.ThrowIfError("Cannot send a packet to the decoder.");
  }
  }
  }

FFMediaToolkit/Decoding/Internal/InputContainer.cs

@@ -71,20 +71,28 @@ public void SeekFile(long targetTs, int streamIndex)
  {
  ffmpeg.av_seek_frame(Pointer, streamIndex, targetTs, ffmpeg.AVSEEK_FLAG_BACKWARD).ThrowIfError($"Seek to {targetTs} failed.");
 
- Decoders[streamIndex].FlushUnmanagedBuffers();
- GetPacketFromStream(streamIndex);
+ foreach (var decoder in Decoders)
+ {
+ decoder?.DiscardBufferedData();
+ }
  }
 
  /// <summary>
  /// Reads a packet from the specified stream index and buffers it in the respective codec.
  /// </summary>
  /// <param name="streamIndex">Index of the stream to read from.</param>
- public void GetPacketFromStream(int streamIndex)
+ /// <returns>True if the requested packet was read, false if EOF ocurred and a flush packet was send to the buffer.</returns>
+ public bool GetPacketFromStream(int streamIndex)
  {
  MediaPacket packet;
  do
  {
- packet = ReadPacket();
+ if (!TryReadNextPacket(out packet))
+ {
+ Decoders[streamIndex].BufferPacket(MediaPacket.CreateFlushPacket(streamIndex));
+ return false;
+ }
+
  var stream = Decoders[packet.StreamIndex];
  if (stream == null)
  {
@@ -98,6 +106,7 @@ public void GetPacketFromStream(int streamIndex)
  }
  }
  while (packet?.StreamIndex != streamIndex);
+ return true;
  }
 
  /// <inheritdoc/>
@@ -190,22 +199,26 @@ private void OpenStreams(MediaOptions options)
  /// <summary>
  /// Reads the next packet from this file.
  /// </summary>
- private MediaPacket ReadPacket()
+ private bool TryReadNextPacket(out MediaPacket packet)
  {
- var pkt = MediaPacket.AllocateEmpty();
- var result = ffmpeg.av_read_frame(Pointer, pkt.Pointer); // Gets the next packet from the file.
+ packet = MediaPacket.AllocateEmpty();
+ var result = ffmpeg.av_read_frame(Pointer, packet.Pointer); // Gets the next packet from the file.
 
  // Check if the end of file error occurred
- if (result == ffmpeg.AVERROR_EOF)
+ if (result < 0)
  {
- throw new EndOfStreamException("End of the file.");
- }
- else
- {
- result.ThrowIfError("Cannot read next packet from the file");
+ packet.Dispose();
+ if (result == ffmpeg.AVERROR_EOF)
+ {
+ return false;
+ }
+ else
+ {
+ result.ThrowIfError("Cannot read next packet from the file");
+ }
  }
 
- return pkt;
+ return true;
  }
  }
 }

FFMediaToolkit/Decoding/MediaStream.cs

@@ -50,12 +50,13 @@ internal MediaStream(Decoder stream, MediaOptions options)
  /// <summary>
  /// Discards all buffered frame data associated with this stream.
  /// </summary>
+ [Obsolete("Do not call this method. Buffered data is automatically discarded when required")]
  public void DiscardBufferedData() => Stream.DiscardBufferedData();
 
  /// <inheritdoc/>
  public virtual void Dispose()
  {
- DiscardBufferedData();
+ Stream.DiscardBufferedData();
  Stream.Dispose();
  }