return -1;   if (!s->slice_height && (s->pict_type != I_TYPE))
static int h263_decode_frame(AVCodecContext *avctx,                              void *data, int *data_size,                             UINT8 *buf, int buf_size){    MpegEncContext *s = avctx->priv_data;    int ret;    AVPicture *pict = data; #ifdef DEBUG    printf("*****frame %d size=%d\n", avctx->frame_number, buf_size);    printf("bytes=%x %x %x %x\n", buf[0], buf[1], buf[2], buf[3]);#endif    /* no supplementary picture */    if (buf_size == 0) {        *data_size = 0;        return 0;    }    init_get_bits(&s->gb, buf, buf_size);    /* let's go :-) */    if (s->h263_msmpeg4) {        ret = msmpeg4_decode_picture_header(s);    } else if (s->h263_pred) {        ret = mpeg4_decode_picture_header(s);    } else if (s->h263_intel) {        ret = intel_h263_decode_picture_header(s);    } else {        ret = h263_decode_picture_header(s);    }    if (ret < 0)        return -1;    /* make sure we start with an I-Frame */    if (!s->slice_height && (s->pict_type != I_TYPE))        return -1;    MPV_frame_start(s);#ifdef DEBUG    printf("qscale=%d\n", s->qscale);#endif    /* decode each macroblock */    for(s->mb_y=0; s->mb_y < s->mb_height; s->mb_y++) {        for(s->mb_x=0; s->mb_x < s->mb_width; s->mb_x++) {#ifdef DEBUG            printf("**mb x=%d y=%d\n", s->mb_x, s->mb_y);#endif            /* DCT & quantize */            if (s->h263_msmpeg4) {                msmpeg4_dc_scale(s);            } else if (s->h263_pred) {                h263_dc_scale(s);            } else {                /* default quantization values */                s->y_dc_scale = 8;                s->c_dc_scale = 8;            }            memset(s->block, 0, sizeof(s->block));            s->mv_dir = MV_DIR_FORWARD;            s->mv_type = MV_TYPE_16X16;             if (s->h263_msmpeg4) {                if (msmpeg4_decode_mb(s, s->block) < 0)                    return -1;            } else {                if (h263_decode_mb(s, s->block) < 0)                    return -1;            }            MPV_decode_mb(s, s->block);        }    }    MPV_frame_end(s);        pict->data[0] = s->current_picture[0];    pict->data[1] = s->current_picture[1];    pict->data[2] = s->current_picture[2];    pict->linesize[0] = s->linesize;    pict->linesize[1] = s->linesize / 2;    pict->linesize[2] = s->linesize / 2;    avctx->quality = s->qscale;    *data_size = sizeof(AVPicture);    return buf_size;}