From 4cfb0d871d4885a88061410ab8f3583018c1ac57 Mon Sep 17 00:00:00 2001 From: Kostya Shishkov Date: Tue, 17 Jul 2012 18:12:41 +0200 Subject: tscc2: do not add/subtract 128 bias during DCT It turns out that the reference decoder subtracts 128 from DC during block decode but adds it back during reordering block with zigzag pattern. Transforming block with incorrect DC caused heavy visual artifacts for many quantisers. --- libavcodec/tscc2.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'libavcodec/tscc2.c') diff --git a/libavcodec/tscc2.c b/libavcodec/tscc2.c index 91f79e249d..5248c9f4ec 100644 --- a/libavcodec/tscc2.c +++ b/libavcodec/tscc2.c @@ -95,7 +95,7 @@ static av_cold int init_vlcs(TSCC2Context *c) OP(d3, 5 * ((s0) - (s1) + (s2)) - 2 * (s3)); \ #define COL_OP(a, b) a = b -#define ROW_OP(a, b) a = (((b) + 0x20) >> 6) + 0x80 +#define ROW_OP(a, b) a = ((b) + 0x20) >> 6 static void tscc2_idct4_put(int *in, int q[3], uint8_t *dst, int stride) { @@ -158,7 +158,7 @@ static int tscc2_decode_mb(TSCC2Context *c, int *q, int vlc_set, } dc = (dc + prev_dc) & 0xFF; prev_dc = dc; - c->block[0] = dc - 0x80; + c->block[0] = dc; nc = get_vlc2(gb, c->nc_vlc[vlc_set].table, 9, 1); if (nc == -1) -- cgit v1.2.3