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[FFmpeg-devel] avcodec/vp8: Fix wrong vpx_rac_is_end() check

Message ID 20221116084412.2537585-1-hiroh@chromium.org
State New
Headers show
Series [FFmpeg-devel] avcodec/vp8: Fix wrong vpx_rac_is_end() check | expand

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Commit Message

Hirokazu Honda Nov. 16, 2022, 8:44 a.m. UTC
The check of vpx_rac_is_end check(s) are added originally from
1afd246960202917e244c844c534e9c1e3c323f5. It causes a regression
of some vp8 stream. b6b9ac5698c8f911841b469af77199153278c55c fixes
the regression by a sort of band-aid way. This fixes the wrongness
of the original commit. vpx_rac_is_end() should be called against
the bool decoder for the vp8 headr context, not one for each
coefficient. Reference is vp8_dixie_tokens_process_row() in token.c
in spec 20.16.

Fixes: Ticket 8069
Fixes: regression of 1afd246960202917e244c844c534e9c1e3c323f5.
Fixes: b6b9ac5698c8f911841b469af77199153278c55c

Signed-off-by: Hirokazu Honda <hiroh@chromium.org>
---
 libavcodec/vp8.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Comments

Ronald S. Bultje Nov. 16, 2022, 1:20 p.m. UTC | #1
Hi,

On Wed, Nov 16, 2022 at 3:44 AM Hirokazu Honda <hiroh@chromium.org> wrote:

> The check of vpx_rac_is_end check(s) are added originally from
> 1afd246960202917e244c844c534e9c1e3c323f5. It causes a regression
> of some vp8 stream. b6b9ac5698c8f911841b469af77199153278c55c fixes
> the regression by a sort of band-aid way. This fixes the wrongness
> of the original commit. vpx_rac_is_end() should be called against
> the bool decoder for the vp8 headr context, not one for each
> coefficient. Reference is vp8_dixie_tokens_process_row() in token.c
> in spec 20.16.
>
> Fixes: Ticket 8069
> Fixes: regression of 1afd246960202917e244c844c534e9c1e3c323f5.
> Fixes: b6b9ac5698c8f911841b469af77199153278c55c
>
> Signed-off-by: Hirokazu Honda <hiroh@chromium.org>
> ---
>  libavcodec/vp8.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/libavcodec/vp8.c b/libavcodec/vp8.c
> index 67f36d8933..77f5a6b657 100644
> --- a/libavcodec/vp8.c
> +++ b/libavcodec/vp8.c
> @@ -2404,7 +2404,8 @@ static av_always_inline int
> decode_mb_row_no_filter(AVCodecContext *avctx, void
>      int num_jobs = s->num_jobs;
>      const VP8Frame *prev_frame = s->prev_frame;
>      VP8Frame *curframe = s->curframe;
> -    VPXRangeCoder *c  = &s->coeff_partition[mb_y &
> (s->num_coeff_partitions - 1)];
> +    VPXRangeCoder *coeff_c  = &s->coeff_partition[mb_y &
> (s->num_coeff_partitions - 1)];
> +
>      VP8Macroblock *mb;
>      uint8_t *dst[3] = {
>          curframe->tf.f->data[0] + 16 * mb_y * s->linesize,
> @@ -2412,7 +2413,7 @@ static av_always_inline int
> decode_mb_row_no_filter(AVCodecContext *avctx, void
>          curframe->tf.f->data[2] +  8 * mb_y * s->uvlinesize
>      };
>
> -    if (vpx_rac_is_end(c))
> +    if (vpx_rac_is_end(&s->c))
>           return AVERROR_INVALIDDATA;
>
>      if (mb_y == 0)
> @@ -2443,7 +2444,7 @@ static av_always_inline int
> decode_mb_row_no_filter(AVCodecContext *avctx, void
>      td->mv_bounds.mv_max.x = ((s->mb_width - 1) << 6) + MARGIN;
>
>      for (mb_x = 0; mb_x < s->mb_width; mb_x++, mb_xy++, mb++) {
> -        if (vpx_rac_is_end(c))
> +        if (vpx_rac_is_end(&s->c))
>              return AVERROR_INVALIDDATA;
>          // Wait for previous thread to read mb_x+2, and reach mb_y-1.
>          if (prev_td != td) {
> @@ -2471,7 +2472,7 @@ static av_always_inline int
> decode_mb_row_no_filter(AVCodecContext *avctx, void
>          prefetch_motion(s, mb, mb_x, mb_y, mb_xy, VP8_FRAME_PREVIOUS);
>
>          if (!mb->skip)
> -            decode_mb_coeffs(s, td, c, mb, s->top_nnz[mb_x],
> td->left_nnz, is_vp7);
> +            decode_mb_coeffs(s, td, coeff_c, mb, s->top_nnz[mb_x],
> td->left_nnz, is_vp7);
>
>          if (mb->mode <= MODE_I4x4)
>              intra_predict(s, td, dst, mb, mb_x, mb_y, is_vp7);
> --
> 2.38.1.431.g37b22c650d-goog
>

Thanks for the fix. So, you're transferring the truncation check from the
per-slice coef buffer to the "main" mode/mv buffer. Shouldn't we check
both? Or is one of them allowed to be truncated? (That seems unlikely, but
that appears to be what you're suggesting here, otherwise there wouldn't be
any artifacts.) If that *is* the case, this needs a comment somewhere,
otherwise we'll forget this over time.

Ronald
Ronald S. Bultje Nov. 16, 2022, 1:22 p.m. UTC | #2
Hi,

On Wed, Nov 16, 2022 at 8:20 AM Ronald S. Bultje <rsbultje@gmail.com> wrote:

> On Wed, Nov 16, 2022 at 3:44 AM Hirokazu Honda <hiroh@chromium.org> wrote:
>
>> @@ -2471,7 +2472,7 @@ static av_always_inline int
>> decode_mb_row_no_filter(AVCodecContext *avctx, void
>>          prefetch_motion(s, mb, mb_x, mb_y, mb_xy, VP8_FRAME_PREVIOUS);
>>
>>          if (!mb->skip)
>> -            decode_mb_coeffs(s, td, c, mb, s->top_nnz[mb_x],
>> td->left_nnz, is_vp7);
>> +            decode_mb_coeffs(s, td, coeff_c, mb, s->top_nnz[mb_x],
>> td->left_nnz, is_vp7);
>>
>>          if (mb->mode <= MODE_I4x4)
>>              intra_predict(s, td, dst, mb, mb_x, mb_y, is_vp7);
>> --
>> 2.38.1.431.g37b22c650d-goog
>>
>
> Thanks for the fix. So, you're transferring the truncation check from the
> per-slice coef buffer to the "main" mode/mv buffer. Shouldn't we check
> both? Or is one of them allowed to be truncated? (That seems unlikely, but
> that appears to be what you're suggesting here, otherwise there wouldn't be
> any artifacts.)
>

To clarify: I think a vpx_rac_is_end(coeff_c) in the "if (!mb->skip)"
branch here would be helpful, I think. Outside, we don't use coeff_c, so no
truncation check is needed. Assuming that still fixes the issue, then.

Ronald
diff mbox series

Patch

diff --git a/libavcodec/vp8.c b/libavcodec/vp8.c
index 67f36d8933..77f5a6b657 100644
--- a/libavcodec/vp8.c
+++ b/libavcodec/vp8.c
@@ -2404,7 +2404,8 @@  static av_always_inline int decode_mb_row_no_filter(AVCodecContext *avctx, void
     int num_jobs = s->num_jobs;
     const VP8Frame *prev_frame = s->prev_frame;
     VP8Frame *curframe = s->curframe;
-    VPXRangeCoder *c  = &s->coeff_partition[mb_y & (s->num_coeff_partitions - 1)];
+    VPXRangeCoder *coeff_c  = &s->coeff_partition[mb_y & (s->num_coeff_partitions - 1)];
+
     VP8Macroblock *mb;
     uint8_t *dst[3] = {
         curframe->tf.f->data[0] + 16 * mb_y * s->linesize,
@@ -2412,7 +2413,7 @@  static av_always_inline int decode_mb_row_no_filter(AVCodecContext *avctx, void
         curframe->tf.f->data[2] +  8 * mb_y * s->uvlinesize
     };
 
-    if (vpx_rac_is_end(c))
+    if (vpx_rac_is_end(&s->c))
          return AVERROR_INVALIDDATA;
 
     if (mb_y == 0)
@@ -2443,7 +2444,7 @@  static av_always_inline int decode_mb_row_no_filter(AVCodecContext *avctx, void
     td->mv_bounds.mv_max.x = ((s->mb_width - 1) << 6) + MARGIN;
 
     for (mb_x = 0; mb_x < s->mb_width; mb_x++, mb_xy++, mb++) {
-        if (vpx_rac_is_end(c))
+        if (vpx_rac_is_end(&s->c))
             return AVERROR_INVALIDDATA;
         // Wait for previous thread to read mb_x+2, and reach mb_y-1.
         if (prev_td != td) {
@@ -2471,7 +2472,7 @@  static av_always_inline int decode_mb_row_no_filter(AVCodecContext *avctx, void
         prefetch_motion(s, mb, mb_x, mb_y, mb_xy, VP8_FRAME_PREVIOUS);
 
         if (!mb->skip)
-            decode_mb_coeffs(s, td, c, mb, s->top_nnz[mb_x], td->left_nnz, is_vp7);
+            decode_mb_coeffs(s, td, coeff_c, mb, s->top_nnz[mb_x], td->left_nnz, is_vp7);
 
         if (mb->mode <= MODE_I4x4)
             intra_predict(s, td, dst, mb, mb_x, mb_y, is_vp7);