static inline int mdec_decode_block_intra(MDECContext *a, int16_t *block, int n) { int level, diff, i, j, run; int component; RLTable *rl = &ff_rl_mpeg1; uint8_t * const scantable = a->scantable.permutated; const uint16_t *quant_matrix = ff_mpeg1_default_intra_matrix; const int qscale = a->qscale; /* DC coefficient */ if (a->version == 2) { block[0] = 2 * get_sbits(&a->gb, 10) + 1024; } else { component = (n <= 3 ? 0 : n - 4 + 1); diff = decode_dc(&a->gb, component); if (diff >= 0xffff) return AVERROR_INVALIDDATA; a->last_dc[component] += diff; block[0] = a->last_dc[component] << 3; } i = 0; { OPEN_READER(re, &a->gb); /* now quantify & encode AC coefficients */ for (;;) { UPDATE_CACHE(re, &a->gb); GET_RL_VLC(level, run, re, &a->gb, rl->rl_vlc[0], TEX_VLC_BITS, 2, 0); if (level == 127) { break; } else if (level != 0) { i += run; if (i > 63) { av_log(a->avctx, AV_LOG_ERROR, "ac-tex damaged at %d %d\n", a->mb_x, a->mb_y); return AVERROR_INVALIDDATA; } j = scantable[i]; level = (level * qscale * quant_matrix[j]) >> 3; level = (level ^ SHOW_SBITS(re, &a->gb, 1)) - SHOW_SBITS(re, &a->gb, 1); LAST_SKIP_BITS(re, &a->gb, 1); } else { /* escape */ run = SHOW_UBITS(re, &a->gb, 6)+1; LAST_SKIP_BITS(re, &a->gb, 6); UPDATE_CACHE(re, &a->gb); level = SHOW_SBITS(re, &a->gb, 10); SKIP_BITS(re, &a->gb, 10); i += run; if (i > 63) { av_log(a->avctx, AV_LOG_ERROR, "ac-tex damaged at %d %d\n", a->mb_x, a->mb_y); return AVERROR_INVALIDDATA; } j = scantable[i]; if (level < 0) { level = -level; level = (level * qscale * quant_matrix[j]) >> 3; level = (level - 1) | 1; level = -level; } else { level = (level * qscale * quant_matrix[j]) >> 3; level = (level - 1) | 1; } } block[j] = level; } CLOSE_READER(re, &a->gb); } a->block_last_index[n] = i; return 0; }