[FFmpeg-devel] [PATCH] mpeg2dec: fix decoding field pictures
Nekopanda
pianoyayaninth at yahoo.co.jp
Thu Feb 8 19:03:24 EET 2018
- Fix field selection for skipped macroblocks
For B field pictures, the spec says,
> The prediction shall be made from the field of the same parity as the field being predicted.
I did it.
- Fix motion vector rounding for chroma components
In 16x8 motion compensation, for lower 16x8 region, the input to mpeg_motion() for motion_y was "motion_y + 16", which causes wrong rounding. For 4:2:0, chroma scaling for y is dividing by two and rounding toward zero. When motion_y < 0 and motion_y + 16 > 0, the rounding direction of "motion_y" and "motion_y + 16" is different and rounding "motion_y + 16" would be incorrect.
We should input "motion_y" as is to round correctly. I add "is_16x8" flag to do that.
---
libavcodec/mpeg12dec.c | 2 ++
libavcodec/mpegvideo_motion.c | 30 ++++++++++++++++--------------
2 files changed, 18 insertions(+), 14 deletions(-)
diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
index f5f2c69..9e076e8 100644
--- a/libavcodec/mpeg12dec.c
+++ b/libavcodec/mpeg12dec.c
@@ -1969,6 +1969,8 @@ static int mpeg_decode_slice(MpegEncContext *s, int mb_y,
s->mv[0][0][1] = s->last_mv[0][0][1];
s->mv[1][0][0] = s->last_mv[1][0][0];
s->mv[1][0][1] = s->last_mv[1][0][1];
+ s->field_select[0][0] = (s->picture_structure - 1) & 1;
+ s->field_select[1][0] = (s->picture_structure - 1) & 1;
}
}
}
diff --git a/libavcodec/mpegvideo_motion.c b/libavcodec/mpegvideo_motion.c
index c913504..5624c10 100644
--- a/libavcodec/mpegvideo_motion.c
+++ b/libavcodec/mpegvideo_motion.c
@@ -239,20 +239,22 @@ void mpeg_motion_internal(MpegEncContext *s,
int motion_y,
int h,
int is_mpeg12,
+ int is_16x8,
int mb_y)
{
uint8_t *ptr_y, *ptr_cb, *ptr_cr;
int dxy, uvdxy, mx, my, src_x, src_y,
- uvsrc_x, uvsrc_y, v_edge_pos;
+ uvsrc_x, uvsrc_y, v_edge_pos, block_y_half;
ptrdiff_t uvlinesize, linesize;
v_edge_pos = s->v_edge_pos >> field_based;
linesize = s->current_picture.f->linesize[0] << field_based;
uvlinesize = s->current_picture.f->linesize[1] << field_based;
+ block_y_half = (field_based | is_16x8);
dxy = ((motion_y & 1) << 1) | (motion_x & 1);
src_x = s->mb_x * 16 + (motion_x >> 1);
- src_y = (mb_y << (4 - field_based)) + (motion_y >> 1);
+ src_y = (mb_y << (4 - block_y_half)) + (motion_y >> 1);
if (!is_mpeg12 && s->out_format == FMT_H263) {
if ((s->workaround_bugs & FF_BUG_HPEL_CHROMA) && field_based) {
@@ -260,7 +262,7 @@ void mpeg_motion_internal(MpegEncContext *s,
my = motion_y >> 1;
uvdxy = ((my & 1) << 1) | (mx & 1);
uvsrc_x = s->mb_x * 8 + (mx >> 1);
- uvsrc_y = (mb_y << (3 - field_based)) + (my >> 1);
+ uvsrc_y = (mb_y << (3 - block_y_half)) + (my >> 1);
} else {
uvdxy = dxy | (motion_y & 2) | ((motion_x & 2) >> 1);
uvsrc_x = src_x >> 1;
@@ -279,7 +281,7 @@ void mpeg_motion_internal(MpegEncContext *s,
my = motion_y / 2;
uvdxy = ((my & 1) << 1) | (mx & 1);
uvsrc_x = s->mb_x * 8 + (mx >> 1);
- uvsrc_y = (mb_y << (3 - field_based)) + (my >> 1);
+ uvsrc_y = (mb_y << (3 - block_y_half)) + (my >> 1);
} else {
if (s->chroma_x_shift) {
// Chroma422
@@ -370,18 +372,18 @@ static void mpeg_motion(MpegEncContext *s,
uint8_t *dest_y, uint8_t *dest_cb, uint8_t *dest_cr,
int field_select, uint8_t **ref_picture,
op_pixels_func (*pix_op)[4],
- int motion_x, int motion_y, int h, int mb_y)
+ int motion_x, int motion_y, int h, int is_16x8, int mb_y)
{
#if !CONFIG_SMALL
if (s->out_format == FMT_MPEG1)
mpeg_motion_internal(s, dest_y, dest_cb, dest_cr, 0, 0,
field_select, ref_picture, pix_op,
- motion_x, motion_y, h, 1, mb_y);
+ motion_x, motion_y, h, 1, is_16x8, mb_y);
else
#endif
mpeg_motion_internal(s, dest_y, dest_cb, dest_cr, 0, 0,
field_select, ref_picture, pix_op,
- motion_x, motion_y, h, 0, mb_y);
+ motion_x, motion_y, h, 0, is_16x8, mb_y);
}
static void mpeg_motion_field(MpegEncContext *s, uint8_t *dest_y,
@@ -395,12 +397,12 @@ static void mpeg_motion_field(MpegEncContext *s, uint8_t *dest_y,
if (s->out_format == FMT_MPEG1)
mpeg_motion_internal(s, dest_y, dest_cb, dest_cr, 1,
bottom_field, field_select, ref_picture, pix_op,
- motion_x, motion_y, h, 1, mb_y);
+ motion_x, motion_y, h, 1, 0, mb_y);
else
#endif
mpeg_motion_internal(s, dest_y, dest_cb, dest_cr, 1,
bottom_field, field_select, ref_picture, pix_op,
- motion_x, motion_y, h, 0, mb_y);
+ motion_x, motion_y, h, 0, 0, mb_y);
}
// FIXME: SIMDify, avg variant, 16x16 version
@@ -870,7 +872,7 @@ static av_always_inline void mpv_motion_internal(MpegEncContext *s,
} else {
mpeg_motion(s, dest_y, dest_cb, dest_cr, 0,
ref_picture, pix_op,
- s->mv[dir][0][0], s->mv[dir][0][1], 16, mb_y);
+ s->mv[dir][0][0], s->mv[dir][0][1], 16, 0, mb_y);
}
break;
case MV_TYPE_8X8:
@@ -907,7 +909,7 @@ static av_always_inline void mpv_motion_internal(MpegEncContext *s,
mpeg_motion(s, dest_y, dest_cb, dest_cr,
s->field_select[dir][0],
ref_picture, pix_op,
- s->mv[dir][0][0], s->mv[dir][0][1], 16, mb_y >> 1);
+ s->mv[dir][0][0], s->mv[dir][0][1], 16, 0, mb_y >> 1);
}
break;
case MV_TYPE_16X8:
@@ -924,8 +926,8 @@ static av_always_inline void mpv_motion_internal(MpegEncContext *s,
mpeg_motion(s, dest_y, dest_cb, dest_cr,
s->field_select[dir][i],
ref2picture, pix_op,
- s->mv[dir][i][0], s->mv[dir][i][1] + 16 * i,
- 8, mb_y >> 1);
+ s->mv[dir][i][0], s->mv[dir][i][1],
+ 8, 1, (mb_y & ~1) + i);
dest_y += 16 * s->linesize;
dest_cb += (16 >> s->chroma_y_shift) * s->uvlinesize;
@@ -952,7 +954,7 @@ static av_always_inline void mpv_motion_internal(MpegEncContext *s,
s->picture_structure != i + 1,
ref_picture, pix_op,
s->mv[dir][2 * i][0], s->mv[dir][2 * i][1],
- 16, mb_y >> 1);
+ 16, 0, mb_y >> 1);
// after put we make avg of the same block
pix_op = s->hdsp.avg_pixels_tab;
--
2.6.3.windows.1
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