static int xan_decode_chroma(AVCodecContext *avctx, unsigned chroma_off) { XanContext *s = avctx->priv_data; uint8_t *U, *V; int val, uval, vval; int i, j; const uint8_t *src, *src_end; const uint8_t *table; int mode, offset, dec_size; if (!chroma_off) return 0; if (chroma_off + 4 >= bytestream2_get_bytes_left(&s->gb)) { av_log(avctx, AV_LOG_ERROR, "Invalid chroma block position\n"); return -1; } bytestream2_seek(&s->gb, chroma_off + 4, SEEK_SET); mode = bytestream2_get_le16(&s->gb); table = s->gb.buffer; offset = bytestream2_get_le16(&s->gb) * 2; if (offset >= bytestream2_get_bytes_left(&s->gb)) { av_log(avctx, AV_LOG_ERROR, "Invalid chroma block offset\n"); return -1; } bytestream2_skip(&s->gb, offset); memset(s->scratch_buffer, 0, s->buffer_size); dec_size = xan_unpack(s, s->scratch_buffer, s->buffer_size); if (dec_size < 0) { av_log(avctx, AV_LOG_ERROR, "Chroma unpacking failed\n"); return -1; } U = s->pic.data[1]; V = s->pic.data[2]; src = s->scratch_buffer; src_end = src + dec_size; if (mode) { for (j = 0; j < avctx->height >> 1; j++) { for (i = 0; i < avctx->width >> 1; i++) { val = *src++; if (val) { val = AV_RL16(table + (val << 1)); uval = (val >> 3) & 0xF8; vval = (val >> 8) & 0xF8; U[i] = uval | (uval >> 5); V[i] = vval | (vval >> 5); } if (src == src_end) return 0; } U += s->pic.linesize[1]; V += s->pic.linesize[2]; } } else { uint8_t *U2 = U + s->pic.linesize[1]; uint8_t *V2 = V + s->pic.linesize[2]; for (j = 0; j < avctx->height >> 2; j++) { for (i = 0; i < avctx->width >> 1; i += 2) { val = *src++; if (val) { val = AV_RL16(table + (val << 1)); uval = (val >> 3) & 0xF8; vval = (val >> 8) & 0xF8; U[i] = U[i+1] = U2[i] = U2[i+1] = uval | (uval >> 5); V[i] = V[i+1] = V2[i] = V2[i+1] = vval | (vval >> 5); } } U += s->pic.linesize[1] * 2; V += s->pic.linesize[2] * 2; U2 += s->pic.linesize[1] * 2; V2 += s->pic.linesize[2] * 2; } } return 0; }