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• iOS video streaming to server using websockets

  6 septembre 2013, par user1516711

  Is it any way possible to stream video frames live from iOS SDK using AVCaptureSession to a remote server using WebSocket like SocketRocket ? What are pros and cons if it is possible ?

• Correct Use Of avcodec_encode_video2() Flush

  5 février 2016, par mFeinstein

  I have a camera sending pictures to a callback function and I want to make a movie with this pictures using FFmpeg. I have followed the decoding_encoding example here but am not sure how to use the got_output for flushing the encoder and getting the delayed frames.

  1. Shoud I encode all my camera’s pictures when they arrive, and later when I want to stop capturing and close the video, I do the flush loop ?

  Or

  2. Should I do the flush periodically, let’s say, every 100 pictures received ?

  My video capture program could be running for hours, so I am worried about how this delayed frames work in memory consumption, if they stack up there until the flush, this could take all my memory.

  ---

  This is the encoding performed by the example, it makes 25 dummy Frames for 1 second of video, and later, in the end, it loop through avcodec_encode_video2() looking for got_output for delayed frames :

  /////  Prepare the Frame, CodecContext and some aditional logic.....
  
  
  
  /* encode 1 second of video */
  
  for (i = 0; i < 25; i++) {
  
      av_init_packet(&pkt);
  
      pkt.data = NULL;    // packet data will be allocated by the encoder
  
      pkt.size = 0;
  
      fflush(stdout);
  
      /* prepare a dummy image */
  
      /* Y */
  
      for (y = 0; y < c->height; y++) {
  
          for (x = 0; x < c->width; x++) {
  
              frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
  
          }
  
      }
  
      /* Cb and Cr */
  
      for (y = 0; y < c->height/2; y++) {
  
          for (x = 0; x < c->width/2; x++) {
  
              frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;
  
              frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;
  
          }
  
      }
  
      frame->pts = i;
  
      /* encode the image */
  
      ret = avcodec_encode_video2(c, &pkt, frame, &got_output);
  
      if (ret < 0) {
  
          fprintf(stderr, "Error encoding frame\n");
  
          exit(1);
  
      }
  
      if (got_output) {
  
          printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
          fwrite(pkt.data, 1, pkt.size, f);
  
          av_free_packet(&pkt);
  
      }
  
  }
  
  /* get the delayed frames */
  
  for (got_output = 1; got_output; i++) {
  
      fflush(stdout);
  
      ret = avcodec_encode_video2(c, &pkt, NULL, &got_output);
  
      if (ret < 0) {
  
          fprintf(stderr, "Error encoding frame\n");
  
          exit(1);
  
      }
  
      if (got_output) {
  
          printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
          fwrite(pkt.data, 1, pkt.size, f);
  
          av_free_packet(&pkt);
  
      }
  
  }
  
  
  
  /////  Closes the file and finishes.....

• Can I specify unique pts for each frame in commandline ? [closed]

  24 septembre 2024, par postscripter

  I have a bunch of jpeg pictures, say four : 01.jpg, 05jpg, 12.jpg and 13.jpg. Can I create an mjpeg/mp4 with variable framerate, consisting of exactly four frames with pts = 01 sec, 05 sec, 12 sec and 13 sec respectively ? Without duplicating or looping them ? I believe it can be done with ffmpeg API, but I'm limited to cmd only.