int ff_h264_check_intra_pred_mode(H264Context *h, int mode){ MpegEncContext * const s = &h->s; static const int8_t top [7]= {LEFT_DC_PRED8x8, 1,-1,-1}; static const int8_t left[7]= { TOP_DC_PRED8x8,-1, 2,-1,DC_128_PRED8x8}; if(mode > 6U) { av_log(h->s.avctx, AV_LOG_ERROR, "out of range intra chroma pred mode at %d %d\n", s->mb_x, s->mb_y); return -1; } if(!(h->top_samples_available&0x8000)){ mode= top[ mode ]; if(mode<0){ av_log(h->s.avctx, AV_LOG_ERROR, "top block unavailable for requested intra mode at %d %d\n", s->mb_x, s->mb_y); return -1; } } if((h->left_samples_available&0x8080) != 0x8080){ mode= left[ mode ]; if(h->left_samples_available&0x8080){ //mad cow disease mode, aka MBAFF + constrained_intra_pred mode= ALZHEIMER_DC_L0T_PRED8x8 + (!(h->left_samples_available&0x8000)) + 2*(mode == DC_128_PRED8x8); } if(mode<0){ av_log(h->s.avctx, AV_LOG_ERROR, "left block unavailable for requested intra mode at %d %d\n", s->mb_x, s->mb_y); return -1; } } return mode; }