func: static int wc3_read_header(AVFormatContext *s,
  
                             AVFormatParameters *ap)
  
  {
  
      Wc3DemuxContext *wc3 = s->priv_data;
  
      ByteIOContext *pb = s->pb;
  
      unsigned int fourcc_tag;
  
      unsigned int size;
  
      AVStream *st;
  
      unsigned char preamble[WC3_PREAMBLE_SIZE];
  
      int ret = 0;
  
      int current_palette = 0;
  
      int bytes_to_read;
  
      int i;
  
      unsigned char rotate;
  
  
  
      /* default context members */
  
      wc3->width = WC3_DEFAULT_WIDTH;
  
      wc3->height = WC3_DEFAULT_HEIGHT;
  
      wc3->palettes = NULL;
  
      wc3->palette_count = 0;
  
      wc3->pts = 0;
  
      wc3->video_stream_index = wc3->audio_stream_index = 0;
  
  
  
      /* skip the first 3 32-bit numbers */
  
      url_fseek(pb, 12, SEEK_CUR);
  
  
  
      /* traverse through the chunks and load the header information before
  
       * the first BRCH tag */
  
      if ((ret = get_buffer(pb, preamble, WC3_PREAMBLE_SIZE)) !=
  
          WC3_PREAMBLE_SIZE)
  
          return AVERROR(EIO);
  
      fourcc_tag = AV_RL32(&preamble[0]);
  
      size = (AV_RB32(&preamble[4]) + 1) & (~1);
  
  
  
      do {
  
          switch (fourcc_tag) {
  
  
  
          case SOND_TAG:
  
          case INDX_TAG:
  
              /* SOND unknown, INDX unnecessary; ignore both */
  
              url_fseek(pb, size, SEEK_CUR);
  
              break;
  
  
  
          case _PC__TAG:
  
              /* need the number of palettes */
  
              url_fseek(pb, 8, SEEK_CUR);
  
              if ((ret = get_buffer(pb, preamble, 4)) != 4)
  
                  return AVERROR(EIO);
  
              wc3->palette_count = AV_RL32(&preamble[0]);
  
              if((unsigned)wc3->palette_count >= UINT_MAX / PALETTE_SIZE){
  
                  wc3->palette_count= 0;
  
                  return -1;
  
              }
  
              wc3->palettes = av_malloc(wc3->palette_count * PALETTE_SIZE);
  
              break;
  
  
  
          case BNAM_TAG:
  
              /* load up the name */
  
              if ((unsigned)size < 512)
  
                  bytes_to_read = size;
  
              else
  
                  bytes_to_read = 512;
  
              if ((ret = get_buffer(pb, s->title, bytes_to_read)) != bytes_to_read)
  
                  return AVERROR(EIO);
  
              break;
  
  
  
          case SIZE_TAG:
  
              /* video resolution override */
  
              if ((ret = get_buffer(pb, preamble, WC3_PREAMBLE_SIZE)) !=
  
                  WC3_PREAMBLE_SIZE)
  
                  return AVERROR(EIO);
  
              wc3->width = AV_RL32(&preamble[0]);
  
              wc3->height = AV_RL32(&preamble[4]);
  
              break;
  
  
  
          case PALT_TAG:
  
              /* one of several palettes */
  
              if ((unsigned)current_palette >= wc3->palette_count)
  
                  return AVERROR_INVALIDDATA;
  
              if ((ret = get_buffer(pb,
  
                  &wc3->palettes[current_palette * PALETTE_SIZE],
  
                  PALETTE_SIZE)) != PALETTE_SIZE)
  
                  return AVERROR(EIO);
  
  
  
              /* transform the current palette in place */
  
              for (i = current_palette * PALETTE_SIZE;
  
                   i < (current_palette + 1) * PALETTE_SIZE; i++) {
  
                  /* rotate each palette component left by 2 and use the result
  
                   * as an index into the color component table */
  
                  rotate = ((wc3->palettes[i] << 2) & 0xFF) |
  
                           ((wc3->palettes[i] >> 6) & 0xFF);
  
                  wc3->palettes[i] = wc3_pal_lookup[rotate];
  
              }
  
              current_palette++;
  
              break;
  
  
  
          default:
  
              av_log(s, AV_LOG_ERROR, "  unrecognized WC3 chunk: %c%c%c%c (0x%02X%02X%02X%02X)\n",
  
                  preamble[0], preamble[1], preamble[2], preamble[3],
  
                  preamble[0], preamble[1], preamble[2], preamble[3]);
  
              return AVERROR_INVALIDDATA;
  
              break;
  
          }
  
  
  
          if ((ret = get_buffer(pb, preamble, WC3_PREAMBLE_SIZE)) !=
  
              WC3_PREAMBLE_SIZE)
  
              return AVERROR(EIO);
  
          fourcc_tag = AV_RL32(&preamble[0]);
  
          /* chunk sizes are 16-bit aligned */
  
          size = (AV_RB32(&preamble[4]) + 1) & (~1);
  
  
  
      } while (fourcc_tag != BRCH_TAG);
  
  
  
      /* initialize the decoder streams */
  
      st = av_new_stream(s, 0);
  
      if (!st)
  
          return AVERROR(ENOMEM);
  
      av_set_pts_info(st, 33, 1, 90000);
  
      wc3->video_stream_index = st->index;
  
      st->codec->codec_type = CODEC_TYPE_VIDEO;
  
      st->codec->codec_id = CODEC_ID_XAN_WC3;
  
      st->codec->codec_tag = 0;  /* no fourcc */
  
      st->codec->width = wc3->width;
  
      st->codec->height = wc3->height;
  
  
  
      /* palette considerations */
  
      st->codec->palctrl = &wc3->palette_control;
  
  
  
      st = av_new_stream(s, 0);
  
      if (!st)
  
          return AVERROR(ENOMEM);
  
      av_set_pts_info(st, 33, 1, 90000);
  
      wc3->audio_stream_index = st->index;
  
      st->codec->codec_type = CODEC_TYPE_AUDIO;
  
      st->codec->codec_id = CODEC_ID_PCM_S16LE;
  
      st->codec->codec_tag = 1;
  
      st->codec->channels = WC3_AUDIO_CHANNELS;
  
      st->codec->bits_per_sample = WC3_AUDIO_BITS;
  
      st->codec->sample_rate = WC3_SAMPLE_RATE;
  
      st->codec->bit_rate = st->codec->channels * st->codec->sample_rate *
  
          st->codec->bits_per_sample;
  
      st->codec->block_align = WC3_AUDIO_BITS * WC3_AUDIO_CHANNELS;
  
  
  
      return 0;
  
  }
  