Styjun

I'm using an QOpenGL widget to draw frames. However, I'm struggling to get frames by using avcodec_receive_frame. It ended within the block else if (ret == AVERROR(EAGAIN)) and returned -11. I have no idea what made this happen. Also I checked that codecs were fine, so I guess the problem wasn't caused by codecs.

MyDemux.cpp

AVPacket* MyDemux::allocatePacket()

 AVPacket* packet = av_packet_alloc();
 return packet;


AVFrame* MyDemux::allocateFrame()

 AVFrame* frame = av_frame_alloc();
 return frame;


int MyDemux::readFrame(AVPacket* packet)

 mux.lock();
 if (!formatCtx) 
 std::cout << "formaetCtx is null" << std::endl;
 mux.unlock();
 return -1;
 
 int ret = av_read_frame(formatCtx, packet);
 if (ret == AVERROR_EOF) 
 return -2;
 
 if (ret != 0) 
 mux.unlock();
 av_packet_free(&packet);
 return -1;
 
 media_type = packet->stream_index;
 mux.unlock();
 return 0;

MyDecode.cpp

void MyDecode::decode(AVFrame* frame, AVPacket* packet)

 int ret;
 ret = avcodec_send_packet(codecCtx, packet); // this returned 0
 while (ret == 0) 
 ret = avcodec_receive_frame(codecCtx, frame); // this returned -11
 if (ret == AVERROR(EINVAL)) 
 std::cout << "codec issue" << std::endl;
 av_frame_free(&frame);
 return;
 
 else if (ret == AVERROR(EAGAIN)) // program ends here
 std::cout << "output is not available this state" << std::endl;
 av_frame_free(&frame);
 return;
 
 else if (ret == AVERROR(EINVAL)) 
 std::cout << "no more frames" << std::endl;
 av_frame_free(&frame);
 return;
 
 

main.cpp

class MyThread : public QThread

public:

 MyDemux demux;
 MyDecode video_decode;
 myDecode audio_decode;
 MyVideoWidget* videoWidget;
 AVPacket* packet;
 AVFrame* frame;

 void initThread()
 
 char* url = "demo.mp4";
 demux.openFile(url);
 video_decode.openCodec(demux.copy_video_codec_par());
 audio_decode.openCodec(demux.copy_audio_codec_par());
 packet = demux.allocatePacket();
 frame = demux.allocateFrame();
 
 void run()
 
 while (demux.readFrame(packet) != -2) 
 if (demux.get_media_type() == 0) 
 video_decode.decode(frame, packet);
 videoWidget->paintFrame(frame);
 
 else if (demux.get_media_type() == 1) 
 
 
 video_decode.decode(frame, nullptr);
 demux.clear();
 demux.close();
 
;

There is a delay between sending and receiving a frame. When receive returns EAGAIN, you should call send with the next encoded frame, then call receive again.