Function vp3_decode_init

libavcodec/vp3.c:2356–2500

}

static av_cold int vp3_decode_init(AVCodecContext *avctx)
{
    static AVOnce init_static_once = AV_ONCE_INIT;
    Vp3DecodeContext *s = avctx->priv_data;
    int ret;
    int c_width;
    int c_height;
    int y_fragment_count, c_fragment_count;

    if (avctx->codec_tag == MKTAG('V', 'P', '4', '0')) {
        s->version = 3;
#if !CONFIG_VP4_DECODER
        av_log(avctx, AV_LOG_ERROR, "This build does not support decoding VP4.\n");
        return AVERROR_DECODER_NOT_FOUND;
#endif
    } else if (avctx->codec_tag == MKTAG('V', 'P', '3', '0'))
        s->version = 0;
    else
        s->version = 1;

    s->avctx  = avctx;
    s->width  = FFALIGN(avctx->coded_width, 16);
    s->height = FFALIGN(avctx->coded_height, 16);
    if (s->width < 18)
        return AVERROR_PATCHWELCOME;
    if (avctx->codec_id != AV_CODEC_ID_THEORA)
        avctx->pix_fmt = AV_PIX_FMT_YUV420P;
    avctx->chroma_sample_location = AVCHROMA_LOC_CENTER;
    ff_hpeldsp_init(&s->hdsp, avctx->flags | AV_CODEC_FLAG_BITEXACT);
    ff_videodsp_init(&s->vdsp, 8);
    ff_vp3dsp_init(&s->vp3dsp);

    for (int i = 0; i < 64; i++) {
#define TRANSPOSE(x) (((x) >> 3) | (((x) & 7) << 3))
        s->idct_permutation[i] = TRANSPOSE(i);
        s->idct_scantable[i]   = TRANSPOSE(ff_zigzag_direct[i]);
#undef TRANSPOSE
    }

    /* initialize to an impossible value which will force a recalculation
     * in the first frame decode */
    for (int i = 0; i < 3; i++)
        s->qps[i] = -1;

    ret = av_pix_fmt_get_chroma_sub_sample(avctx->pix_fmt, &s->chroma_x_shift, &s->chroma_y_shift);
    if (ret)
        return ret;

    s->y_superblock_width  = (s->width  + 31) / 32;
    s->y_superblock_height = (s->height + 31) / 32;
    s->y_superblock_count  = s->y_superblock_width * s->y_superblock_height;

    /* work out the dimensions for the C planes */
    c_width                = s->width >> s->chroma_x_shift;
    c_height               = s->height >> s->chroma_y_shift;
    s->c_superblock_width  = (c_width  + 31) / 32;
    s->c_superblock_height = (c_height + 31) / 32;
    s->c_superblock_count  = s->c_superblock_width * s->c_superblock_height;