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• Revision 97d1f1aaae : Rework scan order fetch logic for decoder Save redundant call for getting predi

  7 juillet 2015, par Jingning Han

  Changed Paths :
   Modify /vp9/decoder/vp9_decodeframe.c

  
   Modify /vp9/decoder/vp9_detokenize.c

  
   Modify /vp9/decoder/vp9_detokenize.h

  
  
  Rework scan order fetch logic for decoder

  Save redundant call for getting prediction mode to obtain scan
  order for detokenization.

  Change-Id : I0683ef119f1579d1261ed5d59052a1745b68ef6f

• C++, FFmpeg, save AVPacket infomation into videostate structure in ffplay.c

  28 mai 2015, par Yoohoo

  I am currently working on a project that tests video streaming. In the project, video stream is encoded with H.264 before send and decoded after receive, using FFmpeg codec and functions.

  I can encode video stream by

  init_video_encode(AV_CODEC_ID_H264);

  where

  static void init_video_encode(AVCodecID codec_id){
  
  codec = avcodec_find_encoder(codec_id);
  
  if (!codec) {
  
      fprintf(stderr, "Codec not found\n");
  
      exit(1);
  
  }
  
  
  
  c = avcodec_alloc_context3(codec);
  
  if (!c) {
  
      fprintf(stderr, "Could not allocate video codec context\n");
  
      exit(1);
  
  }
  
  
  
  /* put sample parameters */
  
  c->bit_rate = 400000;
  
  /* resolution must be a multiple of two */
  
  c->width = 640;
  
  c->height = 480;
  
  /* frames per second */
  
  c->time_base= (AVRational){1,25};
  
  c->gop_size = 10; /* emit one intra frame every ten frames */
  
  c->max_b_frames=max_f;
  
  c->pix_fmt = AV_PIX_FMT_YUV420P;
  
  
  
  if(codec_id == AV_CODEC_ID_H264)
  
      av_opt_set(c->priv_data, "preset", "slow", 0);
  
  
  
  /* open it */
  
  if (avcodec_open2(c, codec, NULL) < 0) {
  
      fprintf(stderr, "Could not open codec\n");
  
      exit(1);
  
  }
  
  
  
  frame = avcodec_alloc_frame();
  
  if (!frame) {
  
      fprintf(stderr, "Could not allocate video frame\n");
  
      exit(1);
  
  }
  
  frame->format = c->pix_fmt;
  
  frame->width  = c->width;
  
  frame->height = c->height;
  
  
  
  /* the image can be allocated by any means and av_image_alloc() is
  
   * just the most convenient way if av_malloc() is to be used */
  
  ret = av_image_alloc(frame->data, frame->linesize, c->width, c->height,
  
                       c->pix_fmt, 32);
  
  
  
  /* get the delayed frames */
  
  if (ret < 0) {
  
      fprintf(stderr, "Could not allocate raw picture buffer\n");
  
      exit(1);
  
  }
  
      av_init_packet(&pkt);
  
  
  
  //}
  
  
  
      pkt.data = NULL;    // packet data will be allocated by the encoder
  
      pkt.size = 0;
  
      //cout<<"\nBefore YUV\n";
  
      if(count == 0)
  
      read_yuv420(frame->data[0]);
  
      count ++;
  
     // cout<<"\nAfter YUV\n";
  
      if(count == SUBSITY) {
  
      count = 0;
  
      }
  
  
  
      frame->pts = i++;
  
  
  
      /* encode the image */
  
      ret = avcodec_encode_video2(c, &pkt, frame, &got_output);
  
      if (ret < 0) {
  
           fprintf(stderr, "Error encoding frame\n");
  
           return -1;
  
      }
  
      //cout<<"\nRecord the Video\n";
  
      if (got_output) {
  
           //printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
           //cout<<"\nBefore Memcpy\n\n\n";
  
  
  
           memcpy(inbufout+totalSize,pkt.data,pkt.size);
  
           //cout<<"\nAfter Memcpy\n\n\n";
  
           totalSize+=pkt.size;

  The video encoder works very well, if I write the encoded packet into a .h264 file, it can be played. But at the decoder side, I cannot decode the received packet with :

      codec = avcodec_find_decoder(AV_CODEC_ID_H264);
  
      if (!codec) {
  
          fprintf(stderr, "Codec not found\n");
  
          exit(1);
  
      }
  
  
  
      c = avcodec_alloc_context3(codec);
  
      if (!c) {
  
          fprintf(stderr, "Could not allocate video codec context\n");
  
          exit(1);
  
      }
  
  
  
      if(codec->capabilities&CODEC_CAP_TRUNCATED)
  
          c->flags|= CODEC_FLAG_TRUNCATED; 
  
  
  
      /* open it */
  
      if (avcodec_open2(c, codec, NULL) < 0) {
  
          fprintf(stderr, "Could not open codec\n");
  
          exit(1);
  
      }
  
  
  
      frame = avcodec_alloc_frame();
  
      if (!frame) {
  
          fprintf(stderr, "Could not allocate video frame\n");
  
          exit(1);
  
      }
  
  len = avcodec_decode_video2(avctx, frame, &got_frame, pkt);
  
      if (len < 0) {
  
          fprintf(stderr, "Error while decoding frame %d\n", *frame_count);
  
          return len;
  
      }

  The reason of failure is lacking parser, I have tried to build a parser but failed......

  Therefore I am wondering using ffplay.c as a header file in my receiver program so that I can use it as the decoder and player.

  I have took a look at ffplay.c, it actually fetch file into a videostate structure and processing it. The fetching part is from line 3188 of ffplay.c :

  VideoState *is;
  
  
  
      is = av_mallocz(sizeof(VideoState));
  
      if (!is)
  
          return NULL;
  
      av_strlcpy(is->filename, filename, sizeof(is->filename));
  
      is->iformat = iformat;
  
      is->ytop    = 0;
  
      is->xleft   = 0;
  
  
  
      /* start video display */
  
      if (frame_queue_init(&is->pictq, &is->videoq, VIDEO_PICTURE_QUEUE_SIZE, 1) < 0)
  
          goto fail;
  
      if (frame_queue_init(&is->subpq, &is->subtitleq, SUBPICTURE_QUEUE_SIZE, 0) < 0)
  
          goto fail;
  
      if (frame_queue_init(&is->sampq, &is->audioq, SAMPLE_QUEUE_SIZE, 1) < 0)
  
          goto fail;
  
  
  
      packet_queue_init(&is->videoq);
  
      packet_queue_init(&is->audioq);
  
      packet_queue_init(&is->subtitleq);
  
  
  
      is->continue_read_thread = SDL_CreateCond();
  
  
  
      init_clock(&is->vidclk, &is->videoq.serial);
  
      init_clock(&is->audclk, &is->audioq.serial);
  
      init_clock(&is->extclk, &is->extclk.serial);
  
      is->audio_clock_serial = -1;
  
      is->av_sync_type = av_sync_type;
  
      is->read_tid     = SDL_CreateThread(read_thread, is);
  
      if (!is->read_tid) {
  
  fail:
  
          stream_close(is);
  
          return NULL;
  
      }

  Now instead of fetching file, I want to modify ffplay.c code so that let it fetch the received packet, I can save received packet to AVPacket by

  static AVPacket avpkt;
  
  avpkt.data = inbuf;

  My question is : how to put AVPacket information into videostate structure ?

• FFMpeg - Save JPGs From Stream

  14 janvier 2018, par user1149620

  I have a multicast UDP video stream. I am trying to write an FFMPEG script that will capture that to JPGs, ideally at the framerate the video is broadcast at (25fps).

  Would someone be able to help let me know the kind of command I need to do this. (I can find commands to update a single JPG, but I would like a continuous stream of JPGs to be saved).

  Thanks