[FFmpeg-devel] [PATCH] avcodec/vc1: fix mquant calculation

[Jerome Borsboom]

In vc1_decode_i_blocks_adv mquant needs to be reset to its default value for
each macroblock, instead of once at the beginning of the slice.

DQPROFILE specifies which macroblocks can have an alternative quantizer step
size. When DQPROFILE specifies edges, the selection is applicable to the edges
of the picture. Slice edges are not selected by DQPROFILE.

Signed-off-by: Jerome Borsboom <jerome.borsboom at carpalis.nl>
---
 libavcodec/vc1_block.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/libavcodec/vc1_block.c b/libavcodec/vc1_block.c
index 0caa5ebb85..f59c440943 100644
--- a/libavcodec/vc1_block.c
+++ b/libavcodec/vc1_block.c
@@ -177,7 +177,7 @@ static void vc1_put_signed_blocks_clamped(VC1Context *v)
             edges = 15;                                        \
         if ((edges&1) && !s->mb_x)                             \
             mquant = -v->altpq;                                \
-        if ((edges&2) && s->first_slice_line)                  \
+        if ((edges&2) && !s->mb_y)                             \
             mquant = -v->altpq;                                \
         if ((edges&4) && s->mb_x == (s->mb_width - 1))         \
             mquant = -v->altpq;                                \
@@ -2626,7 +2626,7 @@ static void vc1_decode_i_blocks_adv(VC1Context *v)
     int cbp, val;
     uint8_t *coded_val;
     int mb_pos;
-    int mquant = v->pq;
+    int mquant;
     int mqdiff;
     GetBitContext *gb = &s->gb;
 
@@ -2671,6 +2671,7 @@ static void vc1_decode_i_blocks_adv(VC1Context *v)
         init_block_index(v);
         for (;s->mb_x < s->mb_width; s->mb_x++) {
             int16_t (*block)[64] = v->block[v->cur_blk_idx];
+            mquant = v->pq;
             ff_update_block_index(s);
             s->bdsp.clear_blocks(block[0]);
             mb_pos = s->mb_x + s->mb_y * s->mb_stride;
-- 
2.13.6