avctx->width = s->width; avctx->height = s->height;
avctx->width  = -((-s->width )>>avctx->lowres); avctx->height = -((-s->height)>>avctx->lowres);
static int av_mpeg4_decode_header(AVCodecParserContext *s1,                                   AVCodecContext *avctx,                                  const uint8_t *buf, int buf_size){    ParseContext1 *pc = s1->priv_data;    MpegEncContext *s = pc->enc;    GetBitContext gb1, *gb = &gb1;    int ret;    s->avctx = avctx;    s->current_picture_ptr = &s->current_picture;    if (avctx->extradata_size && pc->first_picture){        init_get_bits(gb, avctx->extradata, avctx->extradata_size*8);        ret = ff_mpeg4_decode_picture_header(s, gb);    }    init_get_bits(gb, buf, 8 * buf_size);    ret = ff_mpeg4_decode_picture_header(s, gb);    if (s->width) {        avctx->width = s->width;        avctx->height = s->height;    }    pc->first_picture = 0;    return ret;}