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• Get a specific frame from a video using javascript

  25 mars 2016, par Sebi55

  Is there the possibility to somehow get a specified frame from a video using javascript ?
  Most of the questions I found always talked about getting the current frame of a video which is of course no problem but is there a way to get a frame of a video which is not the current one ?
  It would be much easier I think then using ffmpeg from my point of view.
  I actually didn’t find anything about this topic online but I think it is just not possible but maybe someone got an idea.

• P frame dependencies and NAL value

  15 février 2018, par MSD Paul

  Can anyone please tell me what is the difference between this two encoded outputs (N.B. the inputs are same, and the parameters I used while encoding are also same) ?

  For the first set I am getting the NAL value =2 for P frame. for 2nd set I am getting the NAL value for P frames = 0.

  Can anyone tell me which one is possibly cumulatively encoded and which one is directly encoded means P frames only dependent on I frame not on previous P frames.

  output set1 :

  x264 [debug]: frame=   0 QP=28.71 NAL=3 Slice:I Poc:0   I:32768 P:0    SKIP:0    size=335621 bytes
  
  x264 [debug]: frame=   1 QP=29.62 NAL=2 Slice:P Poc:2   I:1028 P:14500 SKIP:17240 size=60797 bytes
  
  x264 [debug]: frame=   2 QP=30.29 NAL=2 Slice:P Poc:4   I:962  P:13307 SKIP:18499 size=61788 bytes
  
  x264 [debug]: frame=   3 QP=30.30 NAL=2 Slice:P Poc:6   I:905  P:13260 SKIP:18603 size=62136 bytes
  
  x264 [debug]: frame=   4 QP=26.45 NAL=3 Slice:I Poc:0   I:32768 P:0    SKIP:0    size=435864 bytes

  output set2 :

  x264 [debug]: frame=   0 QP=28.70 NAL=3 Slice:I Poc:0   I:32768 P:0    SKIP:0    size=335363 bytes
  
  x264 [debug]: frame=   1 QP=33.38 NAL=0 Slice:P Poc:2   I:924  P:11507 SKIP:20337 size=37314 bytes
  
  x264 [debug]: frame=   2 QP=33.28 NAL=0 Slice:P Poc:4   I:1518 P:13596 SKIP:17654 size=55535 bytes
  
  x264 [debug]: frame=   3 QP=33.27 NAL=0 Slice:P Poc:6   I:2211 P:14007 SKIP:16550 size=70488 bytes
  
  x264 [debug]: frame=   4 QP=26.45 NAL=3 Slice:I Poc:0   I:32768 P:0    SKIP:0    size=436369 bytes

• c++ ffmpeg : always the same frame ?

  28 février 2016, par 3DExtended

  I have a code, that (should) give me another frame for each call using ffmpeg. My problem is, that it is always the same frame, that I decode...

  Could someone tell me, what I´m missing here ?

  bool nextFrameFound = false;
  
  while(!nextFrameFound)
  
  {
  
      AVPacket pkt;
  
  
  
      int err = av_read_frame(ctx, &pkt);
  
      if (err < 0)
  
      {
  
          break;
  
          system("Pause");
  
          exit(2);
  
      }
  
  
  
      if (pkt.stream_index == strm)
  
      {
  
          int got = 0;
  
          AVFrame * frame = av_frame_alloc();
  
          int videoFrameBytes = avcodec_decode_video2(codecCtx, frame, &got, &pkt);
  
  
  
          if (got)
  
          {
  
              AVFrame * rgbFrame = av_frame_alloc();
  
  
  
              avpicture_alloc((AVPicture *)rgbFrame, AV_PIX_FMT_RGB24, codecCtx->width, codecCtx->height);
  
              sws_scale(swCtx, frame->data, frame->linesize, 0, frame->height, rgbFrame->data, rgbFrame->linesize);
  
  
  
              for (int i = 0; i < codecCtx->height; i++)
  
              {
  
                  char * data = (char*)rgbFrame->data[0] + i*rgbFrame->linesize[0];
  
                  //process data
  
  
  
              }
  
              nextFrameFound = true;
  
              avcodec_close(codecCtx);
  
  
  
          }
  
  
  
          av_free_packet(&pkt);
  
      }
  
  }
  
  avformat_network_deinit();

  I guess, it is a missunderstanding in using ffmpeg but I can’t help myself :(

  Thanks for your help !