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• libav* incorrect decode

  21 janvier 2012, par jjSunny

  Use libav to save frames from a video.

  The problem is that if you call the function decode a few times, then 2nd and then not correctly handled.

  1st time such a conclusion (all works fine) :

  [swscaler @ 0x8b48510]No accelerated colorspace conversion found from yuv420p to bgra.
  
  good

  2nd (can not find stream, but these are the same) :

  [mp3 @ 0x8ae5800]Header missing
  
  Last message repeated 223 times
  
  [mp3 @ 0x8af31c0]Could not find codec parameters (Audio: mp1, 0 channels, s16)
  
  [mp3 @ 0x8af31c0]Estimating duration from bitrate, this may be inaccurate
  
  av_find_stream_info

  Can you please tell where the error occurred.

  main.cpp

  avcodec_init();
  
  avcodec_register_all();
  
  av_register_all();
  
  char *data;
  
  int size;
  
  //fill data and size
  
  ...
  
  decode(data, size);
  
  decode(data, size);

  video.cpp

  int f_offset = 0;
  
  int f_length = 0;
  
  char *f_data = 0;
  
  
  
  int64_t seekp(void *opaque, int64_t offset, int whence)
  
  {
  
      switch (whence)
  
      {
  
      case SEEK_SET:
  
          if (offset > f_length || offset < 0)
  
              return -1;
  
          f_offset = offset;
  
          return f_offset;
  
      case SEEK_CUR:
  
          if (f_offset + offset > f_length || f_offset + offset < 0)
  
              return -1;
  
          f_offset += offset;
  
          return f_offset;
  
      case SEEK_END:
  
          if (offset > 0 || f_length + offset < 0)
  
              return -1;
  
          f_offset = f_length + offset;
  
          return f_offset;
  
      case AVSEEK_SIZE:
  
          return f_length;
  
      }
  
  
  
      return -1;
  
  }
  
  int readp(void *opaque, uint8_t *buf, int buf_size)
  
  {
  
      if (f_offset == f_length)
  
          return 0;
  
  
  
      int length = buf_size <= (f_length - f_offset) ? buf_size : (f_length - f_offset);
  
  
  
      memcpy(buf, f_data + f_offset, length);
  
      f_offset += length;
  
  
  
      return length;
  
  }
  
  
  
  bool decode(char *data, int length)
  
  {
  
      f_offset = 0;
  
      f_length = length;
  
      f_data = data;
  
  
  
      int buffer_read_size = FF_MIN_BUFFER_SIZE;
  
      uchar *buffer_read = (uchar *) av_mallocz(buffer_read_size + FF_INPUT_BUFFER_PADDING_SIZE);
  
  
  
      AVProbeData pd;
  
      pd.filename = "";
  
      pd.buf_size = 4096 < f_length ? 4096 : f_length;
  
      pd.buf = (uchar *) av_mallocz(pd.buf_size + AVPROBE_PADDING_SIZE);
  
      memcpy(pd.buf, f_data, pd.buf_size);
  
  
  
      AVInputFormat *pAVInputFormat = av_probe_input_format(&pd, 1);
  
      if (pAVInputFormat == NULL)
  
      {
  
          std::cerr << "AVIF";
  
          return false;
  
      }
  
      pAVInputFormat->flags |= AVFMT_NOFILE;
  
  
  
      ByteIOContext ByteIOCtx;
  
      if (init_put_byte(&ByteIOCtx, buffer_read, buffer_read_size, 0, NULL, readp, NULL, seekp) < 0)
  
      {
  
          std::cerr << "init_put_byte";
  
          return false;
  
      }
  
  
  
      AVFormatContext *pFormatCtx;
  
      if (av_open_input_stream(&pFormatCtx, &ByteIOCtx, "", pAVInputFormat, NULL) < 0)
  
      {
  
          std::cerr << "av_open_stream";
  
          return false;
  
      }
  
  
  
      if (av_find_stream_info(pFormatCtx) < 0)
  
      {
  
          std::cerr << "av_find_stream_info";
  
          return false;
  
      }
  
  
  
      int video_stream;
  
      video_stream = -1;
  
      for (uint i = 0; i < pFormatCtx->nb_streams; ++i)
  
          if (pFormatCtx->streams[i]->codec->codec_type == CODEC_TYPE_VIDEO)
  
          {
  
              video_stream = i;
  
              break;
  
          }
  
      if (video_stream == -1)
  
      {
  
          std::cerr << "video_stream == -1";
  
          return false;
  
      }
  
  
  
      AVCodecContext *pCodecCtx;
  
      pCodecCtx = pFormatCtx->streams[video_stream]->codec;
  
  
  
      AVCodec *pCodec;
  
      pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
  
      if (pCodec == NULL)
  
      {
  
          std::cerr << "pCodec == NULL";
  
          return false;
  
      }
  
  
  
      if (avcodec_open(pCodecCtx, pCodec) < 0)
  
      {
  
          std::cerr << "avcodec_open";
  
          return false;
  
      }
  
  
  
      AVFrame *pFrame;
  
      pFrame = avcodec_alloc_frame();
  
      if (pFrame == NULL)
  
      {
  
          std::cerr << "pFrame == NULL";
  
          return false;
  
      }
  
      AVFrame *pFrameRGB;
  
      pFrameRGB = avcodec_alloc_frame();
  
      if (pFrameRGB == NULL)
  
      {
  
          std::cerr << "pFrameRGB == NULL";
  
          return false;
  
      }
  
  
  
      int numBytes;
  
      numBytes = avpicture_get_size(PIX_FMT_RGB32, pCodecCtx->width, pCodecCtx->height);
  
      uint8_t *buffer;
  
      buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));
  
      if (buffer == NULL)
  
      {
  
          std::cerr << "buffer == NULL";
  
          return false;
  
      }
  
  
  
      // Assign appropriate parts of buffer to image planes in pFrameRGB
  
      // Note that pFrameRGB is an AVFrame, but AVFrame is a superset
  
      // of AVPicture
  
      avpicture_fill((AVPicture *) pFrameRGB, buffer, PIX_FMT_RGB32, pCodecCtx->width, pCodecCtx->height);
  
  
  
      SwsContext *swsctx;
  
      swsctx = sws_getContext(
  
                  pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
  
                  pCodecCtx->width, pCodecCtx->height, PIX_FMT_RGB32,
  
                  SWS_BILINEAR, NULL, NULL, NULL);
  
      if (swsctx == NULL)
  
      {
  
          std::cerr << "swsctx == NULL";
  
          return false;
  
      }
  
  
  
      AVPacket packet;
  
      while (av_read_frame(pFormatCtx, &packet) >= 0)
  
      {
  
          if (packet.stream_index == video_stream)
  
          {
  
              int frame_finished;
  
              avcodec_decode_video2(pCodecCtx, pFrame, &frame_finished, &packet);
  
  
  
              if (frame_finished)
  
              {
  
                  sws_scale(swsctx, pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);
  
  
  
                  std::cerr << "good";
  
                  av_close_input_stream(pFormatCtx);
  
  
  
                  return true;
  
              }
  
              else
  
                  std::cerr << "frame_finished == 0";
  
          }
  
      }
  
  
  
      std::cerr << "av_read_frame < 0";
  
      return false;
  
  }

  ffmpeg -version

  FFmpeg 0.6.2-4:0.6.2-1ubuntu1
  
  libavutil     50.15. 1 / 50.15. 1
  
  libavcodec    52.72. 2 / 52.72. 2
  
  libavformat   52.64. 2 / 52.64. 2
  
  libavdevice   52. 2. 0 / 52. 2. 0
  
  libavfilter    1.19. 0 /  1.19. 0
  
  libswscale     0.11. 0 /  0.11. 0
  
  libpostproc   51. 2. 0 / 51. 2. 0

• How to get correct video dimensions

  21 septembre 2011, par David542

  I've been using ffmpeg -i and mediainfo (CLI) to get the dimensions of a video. Unfortunately, neither have been very good at returning the correct dimensions. This is especially true if the video has been modified since its initial export.

  What is the best way to get the correct dimensions of a video file ?

• Anomalie #2374 (Fermé) : request url too long

  17 octobre 2011, par Ben .

  la solution : define(’_CACHE_CONTEXTES_AJAX’,true) ; dans le mes_options.php duplicate #2123