On Tue, Apr 08, 2025 at 07:22:32PM +0800, Bin Peng wrote: > When decoding a bitstream with weighted-bipred enabled, > the results on ARM and x86 platforms may differ. > > The reason for the inconsistency is that the value of > STRIDE_ALIGN differs between platforms. And STRIDE_ALIGN > is set to the buffer stride of temporary buffers for U > and V components in mc_part_weighted. > > If the buffer stride is 32 or 64 (as on x86 platforms), > the U and V pixels can be interleaved row by row without > overlapping, resulting in correct output. > However, on ARM platforms where the stride is 16, > the V component will overwrite part of the U component's pixels, > leading to incorrect predicted pixels. > > The bug can be reproduced by the following bitstream. > > https://trac.ffmpeg.org/attachment/ticket/11357/inter_weighted_bipred2.264 > > And the ref/fate file is also added in this patch. > > Fixes: ticket 11357 > Signed-off-by: Bin Peng <peng...@visionular.com> > --- > libavcodec/utils.c | 4 ++-
> .../h264-conformance-weighted_bipred2.264 | 31 +++++++++++++++++++
is this supposed to be a fate test ?
if so theres something missing also the file extension is a bit misleading
and tests covering more cases is always welcome
> 2 files changed, 34 insertions(+), 1 deletion(-)
> create mode 100644 tests/ref/fate/h264-conformance-weighted_bipred2.264
>
> diff --git a/libavcodec/utils.c b/libavcodec/utils.c
> index 90867ed6b1..5d15f5c8fa 100644
> --- a/libavcodec/utils.c
> +++ b/libavcodec/utils.c
> @@ -144,6 +144,7 @@ void avcodec_align_dimensions2(AVCodecContext *s, int
> *width, int *height,
> int i;
> int w_align = 1;
> int h_align = 1;
> + int stride_align = STRIDE_ALIGN;
> AVPixFmtDescriptor const *desc = av_pix_fmt_desc_get(s->pix_fmt);
>
> if (desc) {
> @@ -339,13 +340,14 @@ void avcodec_align_dimensions2(AVCodecContext *s, int
> *width, int *height,
> // increasing witdth ensure that the temporary area is large enough,
> // the next rounded up width is 32
> *width = FFMAX(*width, 32);
> + stride_align = FFMAX(stride_align, 32);
does the following fix this too ?
diff --git a/libavcodec/h264_mb.c b/libavcodec/h264_mb.c
index 6083f7ad84f..0d6562b5830 100644
--- a/libavcodec/h264_mb.c
+++ b/libavcodec/h264_mb.c
@@ -407,7 +407,7 @@ static av_always_inline void mc_part_weighted(const
H264Context *h, H264SliceCon
/* don't optimize for luma-only case, since B-frames usually
* use implicit weights => chroma too. */
uint8_t *tmp_cb = sl->bipred_scratchpad;
- uint8_t *tmp_cr = sl->bipred_scratchpad + (16 << pixel_shift);
+ uint8_t *tmp_cr = sl->bipred_scratchpad + (8 << pixel_shift +
(chroma_idc == 3));
uint8_t *tmp_y = sl->bipred_scratchpad + 16 * sl->mb_uvlinesize;
int refn0 = sl->ref_cache[0][scan8[n]];
int refn1 = sl->ref_cache[1][scan8[n]];
[...]
--
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