Fix Decoder Invalid Packet Handling

Util/FFmpeg/FFmpegNativeDecoder.cs

@@ -191,6 +191,13 @@ internal sealed unsafe class FFmpegNativeDecoder : IDisposable
     private bool _isOpened;
     private bool _disposed;
     private bool _isDraining;
+
+    /// <summary>Number of video packets skipped because the decoder rejected them as invalid data.</summary>
+    private int _skippedPacketCount;
+
+    /// <summary>Number of skipped packets for which a warning is logged.</summary>
+    private const int MaxLoggedSkippedPackets = 5;
+
     private readonly object _lock = new();
 
     // Fields to detect SwsContext updates
@@ -371,6 +378,16 @@ internal sealed unsafe class FFmpegNativeDecoder : IDisposable
                 if (_videoStreamIndex == -1)
                     throw new Exception("Failed to find video stream.");
 
+                // Only the video stream is used. The demuxer does not need to return the packets of the other streams
+                // (audio, subtitles, ...) once they are marked as discarded.
+                // Reference: AVStream.discard - "Selects which packets can be discarded at will and do not need to be demuxed."
+                // https://ffmpeg.org/doxygen/trunk/structAVStream.html
+                for (int i = 0; i < _pFormatContext->nb_streams; i++)
+                {
+                    if (i != _videoStreamIndex)
+                        _pFormatContext->streams[i]->discard = AVDiscard.AVDISCARD_ALL;
+                }
+
                 var stream = _pFormatContext->streams[_videoStreamIndex];
                 _timeBase = stream->time_base;
 
@@ -441,9 +458,13 @@ internal sealed unsafe class FFmpegNativeDecoder : IDisposable
                     TotalFrames = 0;
                 }
 
-                Duration = _pFormatContext->duration > 0
-                    ? _pFormatContext->duration / (double)ffmpeg.AV_TIME_BASE
-                    : (stream->duration > 0 ? stream->duration * ffmpeg.av_q2d(stream->time_base) : 0);
+                // Duration of the video stream (AVStream.duration, in the stream time base).
+                // When the stream does not carry a duration, the container duration (AVFormatContext.duration,
+                // in AV_TIME_BASE units, the longest of all streams) is used.
+                // Reference: https://ffmpeg.org/doxygen/trunk/structAVStream.html, https://ffmpeg.org/doxygen/trunk/structAVFormatContext.html
+                Duration = stream->duration > 0
+                    ? stream->duration * ffmpeg.av_q2d(stream->time_base)
+                    : _pFormatContext->duration > 0 ? _pFormatContext->duration / (double)ffmpeg.AV_TIME_BASE : 0;
 
                 // 9. Allocate frame and packet buffers
                 // Reference: https://ffmpeg.org/doxygen/trunk/group__lavu__frame.html
@@ -655,6 +676,8 @@ internal sealed unsafe class FFmpegNativeDecoder : IDisposable
     /// <summary>
     /// Reads packets from the container until a packet belonging to the video stream is found,
     /// then sends it to the decoder via <c>avcodec_send_packet</c>.
+    /// A packet that the decoder rejects as invalid data (<c>AVERROR_INVALIDDATA</c>, e.g. a damaged packet)
+    /// is skipped and the next packet is read. Any other decoder error is thrown.
     /// Reference: https://ffmpeg.org/doxygen/trunk/group__lavc__encdec.html
     /// </summary>
     /// <returns>True if a video packet was sent; false on EOF.</returns>
@@ -670,6 +693,18 @@ internal sealed unsafe class FFmpegNativeDecoder : IDisposable
             {
                 ret = ffmpeg.avcodec_send_packet(_pCodecContext, _pPacket);
                 ffmpeg.av_packet_unref(_pPacket);
+
+                if (ret == ffmpeg.AVERROR_INVALIDDATA)
+                {
+                    // The warning is logged for the first few packets only (a damaged file can have many).
+                    _skippedPacketCount++;
+                    if (_skippedPacketCount <= MaxLoggedSkippedPackets)
+                    {
+                        Melon<RenderMod>.Logger.Warning($"[FFmpegNativeDecoder] Skipped an invalid video packet ({_skippedPacketCount}): {GetFFmpegErrorString(ret)}");
+                    }
+                    continue;
+                }
+
                 if (ret < 0)
                 {
                     throw new Exception($"Error sending packet to decoder: {GetFFmpegErrorString(ret)}");