Recherche avancée

Sur d’autres sites (5974)

• libavcodec video decoding not working

  5 février 2013, par Imran

  I am trying to decode video encoded with H264. I am sending AVPacket's data and its size to decoder code. there I am trying to decode the frame and display it on a GUI. problem is when I am decoding the frame it is returning same number of frame byte as the size of packet means it is not decompressing the data. Can any one tell what will be the problem. My encoding program is working fine.

  here is code for encoding

    static struct SwsContext *img_convert_ctx;
  
    pkt.data = NULL;   
  
    pkt.size = 0; 
  
  
  
  
  
    avpicture_fill((AVPicture *)srcFrame, frame,AV_PIX_FMT_BGR24, 640, 480);
  
   if(img_convert_ctx == NULL) {
  
    int w = 640;
  
    int h = 480;
  
    img_convert_ctx = sws_getContext(w, h, 
  
        AV_PIX_FMT_BGR24, c->width, c->height, PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);
  
     if(img_convert_ctx == NULL) {
  
      fprintf(stderr, "Cannot initialize the conversion context!\n");
  
    }
  
  }
  
    sws_scale(img_convert_ctx, srcFrame->data, srcFrame->linesize, 0,480,picture->data, picture->linesize);
  
  
  
  
  
    fflush(stdout);
  
  
  
    picture->pts=counter;
  
  
  
  
  
    ret = avcodec_encode_video2(c, &pkt, picture, &got_output);
  
      if (ret < 0) {
  
          fprintf(stderr, "Error encoding frame\n");
  
      }
  
  
  
      if (got_output) {
  
  
  
          vdec.decode_frame(pkt.data ,pkt.size);
  
  
  
          av_free_packet(&pkt);
  
      }

  decoder code...

      int len ,got_frame;
  
  
  
  avpkt.size = data_length;
  
  
  
  avpkt.data = frame_buffer;
  
  
  
  if(!frame_buffer){
  
  
  
  return "frame buffer empty\n";
  
  
  
  }
  
  
  
  len = avcodec_decode_video2(avctx ,frame ,&got_frame ,&avpkt);
  
  
  
  if( len < 0){
  
  
  
      return "error while decoding\n";
  
  
  
  }
  
  
  
  if( got_frame ){
  
  
  
  static struct SwsContext *img_convert_ctx;  
  
  
  
   if(img_convert_ctx == NULL) {
  
  
  
    img_convert_ctx = sws_getContext(w, h, 
  
        PIX_FMT_YUV420P, avctx->width,
  
        avctx->height, PIX_FMT_BGR24, 
  
        SWS_BICUBIC, NULL, NULL, NULL);
  
  
  
     if(img_convert_ctx == NULL) {
  
  
  
      return  "Cannot initialize the conversion context!\n";
  
  
  
    }
  
  
  
  }
  
  
  
  j=sws_scale(img_convert_ctx, 
  
      frame->data , frame->linesize ,
  
      0, h ,picture->data,
  
      picture->linesize );
  
  
  
  if(j==0){
  
  
  
  exit(1);
  
  
  
  }

  I am initializing all other code like AVCodecContext and Codec into other method.

  Please help me to find the solution.

• avcodec/mpegpicture : Don't copy unnecessarily, fix race

  8 août 2022, par Andreas Rheinhardt

  avcodec/mpegpicture : Don't copy unnecessarily, fix race
  mpegvideo uses an array of Pictures and when it is done with using
  
  them, it only unreferences them incompletely : Some buffers are kept
  
  so that they can be reused lateron if the same slot in the Picture
  
  array is reused, making this a sort of a bufferpool.
  
  (Basically, a Picture is considered used if the AVFrame's buf is set.)
  
  Yet given that other pieces of the decoder may have a reference to
  
  these buffers, they need not be writable and are made writable using
  
  av_buffer_make_writable() when preparing a new Picture. This involves
  
  reading the buffer's data, although the old content of the buffer
  
  need not be retained.
  Worse, this read can be racy, because the buffer can be used by another
  
  thread at the same time. This happens for Real Video 3 and 4.
  This commit fixes this race by no longer copying the data ;
  
  instead the old buffer is replaced by a new, zero-allocated buffer.
  (Here are the details of what happens with three or more decoding threads
  
  when decoding rv30.rm from the FATE-suite as happens in the rv30 test :
  
  The first decoding thread uses the first slot of its picture array
  
  to store its current pic ; update_thread_context copies this for the
  
  second thread that decodes a P-frame. It uses the second slot in its
  
  Picture array to store its P-frame. This arrangement is then copied
  
  to the third decode thread, which decodes a B-frame. It uses the third
  
  slot in its Picture array for its current frame.
  
  update_thread_context copies this to the next thread. It unreferences
  
  the third slot containing the other B-frame and then it reuses this
  
  slot for its current frame. Because the pic array slots are only
  
  incompletely unreferenced, the buffers of the previous B-frame are
  
  still in there and they are not writable ; in fact the previous
  
  thread is concurrently writing to them, causing races when making
  
  the buffer writable.)
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/mpegpicture.c

• flac/metaflac : Limit the size of metadata blocks

  1er mai 2016, par Erik de Castro Lopo

  flac/metaflac : Limit the size of metadata blocks
  Limit allow image file size to slightly less than 2^24 bytes so that
  
  the file size plus extra house keeping data is strictly less that
  
  2^24 bytes in size.
  Patch-from : lvqcl <lvqcl.mail@gmail.com>
  

  • [DH] src/libFLAC/metadata_object.c
  • [DH] src/share/grabbag/picture.c