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• error in hls play video streaming with ffmpeg real time manipulation

  4 août 2019, par Mohsen Rahnamaei

  I am using fluent ffmpeg to write something on video streaming real-time
  means that I am using this tool to write text on every ts file which server wants to serve in order to response the hls request from client :
  in server iam using this code :

  res.setHeader('Content-Type', CONTENT_TYPE.SEGMENT)
  
  res.statusCode = 200
  
  var proc = ffmpeg(req.filePath).videoFilters({
  
        filter: 'drawtext',
  
        options: {
  
          text: 'VERY LONG TEXT VERY VERY VERY VERY LOL!!!',
  
          fontsize: 36,
  
          fontcolor: 'white',
  
          x: '(main_w/2-text_w/2)',
  
          y: '(text_h/2)+15',
  
          shadowcolor: 'black',
  
          shadowx: 2,
  
          shadowy: 2
  
        }
  
      }
  
  
  
    )
  
  
  
  
  
    .videoCodec('libx264')
  
  
  
    .audioCodec('aac')
  
  
  
  
  
    .format('mpegts')
  
  
  
    .on('end', function (stdout, stderr) {
  
  
  
      console.log('Transcoding succeeded !', req.filePath);
  
  
  
    })
  
  
  
    .on('error', function (err) {
  
      console.log('an error happened: ' + err.message);
  
    }).pipe(res, {
  
      end: true
  
    })

  but in client just play first ts file and after that, I get this log in the console :

  [log] > AVC:6798 ms overlapping between fragments detected
  
  blob:http://demo.jwp…a8dc-56b513684988:1 
  
  [log] > Video/PTS/DTS adjusted: 6798/6798,delta:-6798 ms
  
  blob:http://demo.jwp…a8dc-56b513684988:1 

  and a bunch of this log :

  [warn] > Dropping 1 audio frame @ 6.805s due to 6797 ms overlap.

  what should I do ?????

• FFmpeg - avcodec_receive_frame returns 0 but frames are invalid

  9 juillet 2019, par Jinx

  I’ve been trying to extract images from videos, but not those with PNG codec. My code works fine with those with JPEG. avcodec_receive_frame worked successfully but the data of the frames was like trash ? Do I have to do something special to demuxing when dealing with PNG ?

  Exception thrown at 0x00007FFF7DF34B9A (msvcrt.dll) in Program.exe : 0xC0000005 : Access violation reading location 0x00000000000003F0 when calling avcodec_send_frame in my saveImage function, which means I was accessing invalid or unalloacted memory I guess. How this happened ?

  

  Just suppose all the function calls returned 0 until exception thrown.

  Decoding :

  bool ImageExtractor::decode() {
  
      // some other code here
  
      ret = avcodec_send_packet(codec_ctx, packet); // returned 0
  
      ret = avcodec_receive_frame(codec_ctx, frame); // returned 0
  
      if (ret == 0) {
  
          if (count >= target_frame) {
  
              snprintf(buf, sizeof(buf), "%s/%d.png", destination.toLocal8Bit().data(), count);
  
              saveImage(frame, buf); // a function that writes images on disk 
  
         }
  
      // some other code here
  
  }
  
  
  
  
  
  bool ImageExtractor::saveImage(AVFrame *frame, char *destination) {
  
       AVFormatContext *imgFmtCtx = avformat_alloc_context();
  
       pFormatCtx->oformat = av_guess_format("mjpeg", NULL, NULL);
  
  
  
       // some other code here
  
  
  
      if (!frame)
  
          std::cout << "invalid frame \n";
  
  
  
      if (!imgCodecCtx) // AV_CODEC_ID_MJPEG(7)
  
          std::cout << "invalid codec ctx \n";
  
  
  
      ret = avcodec_send_frame(imgCodecCtx, frame); // everything stopped here
  
  }

  Demuxing :

  avformat_open_input(&format_ctx, source.toLocal8Bit(), nullptr, nullptr);
  
  vsi = av_find_best_stream(format_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, nullptr, 0);
  
  codec_par = avcodec_parameters_alloc();
  
  avcodec_parameters_copy(codec_par, format_ctx->streams[vsi]->codecpar);
  
  
  
  AVCodec* codec = avcodec_find_decoder(codec_par->codec_id); // AV_CODEC_ID_PNG(61)
  
  codec_ctx = avcodec_alloc_context3(codec);
  
  avcodec_parameters_to_context(codec_ctx, codec_par);
  
  avcodec_parameters_free(&codec_par);
  
  avcodec_open2(codec_ctx, codec, 0);

• Using ffmpeg's avcodec_receive_frame() and why do I get these vertical lines in the decodec image sometimes

  7 juillet 2019, par Lucas Zanella

  I’m using the modern ffmpeg API which instructs me to use avcodec_send_packet and avcodec_receive_frame. There are literally no examples of usage in github so I couldn’t compare with other code.

  My code kinda works, but sometimes, for less than a second or two, the video gets decoded like this :

  

  I thought it was a buffer size problem, so I increased from

  const size_t bufferSize = 408304;

  to

  const size_t bufferSize = 10408304;

  Just to see but the problem persists.

  (the video size is 1920x1080 and this happens even when there’s little motion in the screen)

  Here’s my decoder class which sends the decoded data to OpenGL in the line
  this->frameUpdater->updateData(avFrame->data, avFrame->width, avFrame->height);

      void  FfmpegDecoder::decodeFrame(uint8_t* frameBuffer, int frameLength)
  
  {
  
      if (frameLength <= 0) return;
  
  
  
      int frameFinished = 0;
  
  
  
      AVPacket* avPacket = av_packet_alloc();
  
      if (!avPacket) std::cout << "av packet error" << std::endl;
  
  
  
      avPacket->size = frameLength;
  
      avPacket->data = frameBuffer;
  
  
  
      //Disable ffmpeg annoying output
  
      av_log_set_level(AV_LOG_QUIET); 
  
  
  
      int sendPacketResult = avcodec_send_packet(avCodecContext, avPacket);
  
      if (!sendPacketResult) {
  
          int receiveFrameResult = avcodec_receive_frame(avCodecContext, avFrame);
  
          if (!receiveFrameResult) {
  
              this->frameUpdater->updateData(avFrame->data, avFrame->width, avFrame->height);
  
          } else if ((receiveFrameResult < 0) && (receiveFrameResult != AVERROR(EAGAIN)) && (receiveFrameResult != AVERROR_EOF)) {
  
              std::cout << "avcodec_receive_frame returned error " << receiveFrameResult /*<< *av_err2str(result).c_str()*/ << std::endl;
  
          } else {
  
              switch (receiveFrameResult) {
  
                  //Not exactly an error, we just have to wait for more data
  
                  case AVERROR(EAGAIN):
  
                      break;
  
                  //To be done: what does this error mean? I think it's literally the end of an mp4 file
  
                  case AVERROR_EOF:
  
                      std::cout << "avcodec_receive_frame AVERROR_EOF" << std::endl;
  
                      break;
  
                  //To be done: describe what error is this in std cout before stopping
  
                  default:
  
                      std::cout << "avcodec_receive_frame returned error, stopping..." << receiveFrameResult /*<< av_err2str(result).c_str()*/ << std::endl;
  
                      break;
  
                  //Error happened, should break anyway
  
                  break;
  
              }
  
          }
  
      } else {
  
          switch (sendPacketResult) {
  
              case AVERROR(EAGAIN):
  
                  std::cout << "avcodec_send_packet EAGAIN" << std::endl;
  
                  break;
  
              case AVERROR_EOF:
  
                  std::cout << "avcodec_send_packet AVERROR_EOF" << std::endl;
  
                  break;
  
              default:
  
                  break;
  
          }
  
      }
  
  
  
  }

  I think that people who knows how decoding works might know instantly why the image gets decoded like this. It’d be very helpful to know why. Thanks !