Fix Zero Duration Of Last Video Frame

Util/FFmpeg/FFmpegNativeEncoder.cs

@@ -1594,6 +1594,16 @@ namespace ADOFAIRenderer.Util.FFmpeg
                     if (response < 0)
                         throw new Exception($"Error occurred while receiving packet from encoder: {GetFFmpegErrorString(response)} (Code: {response})");
 
+                    // Packet duration: 1 tick of the codec time base (1 / framerate), the display time of one frame
+                    // at the constant frame rate of the output. Applied when the encoder leaves it unknown (0).
+                    // The encoders output 0 here because libavcodec clears the frame duration
+                    // unless AV_CODEC_FLAG_FRAME_DURATION is set.
+                    // The mp4/mov muxer takes the length of the last sample from the duration of the last packet;
+                    // with 0 the last frame has no display time and the edit list ends before it.
+                    // Reference: https://github.com/FFmpeg/FFmpeg/blob/release/8.0/libavcodec/encode.c (encode_send_frame_internal: frame duration)
+                    // Reference: https://github.com/FFmpeg/FFmpeg/blob/release/8.0/libavformat/movenc.c (ff_mov_write_packet: track_duration)
+                    if (_pPacket->duration <= 0)
+                        _pPacket->duration = 1;
                     // Convert PTS/DTS from codec timebase → stream timebase
                     ffmpeg.av_packet_rescale_ts(_pPacket, _pCodecContext->time_base, _pVideoStream->time_base);
                     _pPacket->stream_index = _pVideoStream->index;