diff mbox

[FFmpeg-devel] avcodec/vc1_pred: properly clip interlaced motion vectors

Message ID 0310ef16-586e-c2d0-fd90-b4e481eb4e2d@carpalis.nl
State Accepted
Commit c0f154bba506e1cb609b1193632d452b89918a80
Headers show

Commit Message

Jerome Borsboom April 21, 2018, 7:05 p.m. UTC 
> Fixes #2557.
> 
> Signed-off-by: Paul B Mahol <onemda at gmail.com>
> ---
>  libavcodec/vc1_pred.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/libavcodec/vc1_pred.c b/libavcodec/vc1_pred.c
> index 54712f6b7a..9f42a930fe 100644
> --- a/libavcodec/vc1_pred.c
> +++ b/libavcodec/vc1_pred.c
> @@ -98,9 +98,9 @@ static av_always_inline int scaleforsame_y(VC1Context *v, int i, int n /* MV */,
>      }
>  
>      if (v->cur_field_type && !v->ref_field_type[dir])
> -        return av_clip(scaledvalue, -v->range_y / 2 + 1, v->range_y / 2);
> +        return av_clip(scaledvalue, -v->range_y / 2 - 1, v->range_y / 2);
>      else
> -        return av_clip(scaledvalue, -v->range_y / 2, v->range_y / 2 - 1);
> +        return av_clip(scaledvalue, -v->range_y / 2, v->range_y / 2 + 1);
>  }
>  
>  static av_always_inline int scaleforopp_x(VC1Context *v, int n /* MV */)
> -- 
> 2.11.0

scaleforsame_y references ref_field_type. Therefore, it needs to be set
before scaleforsame is called.

Signed-off-by: Jerome Borsboom <jerome.borsboom@carpalis.nl>
---
I am not sure your patch is correct. The existing implementation agrees with VC-1 spec.
See Figure 119 in 10.3.5.4.3.4.2 in particular. Please have a look if the patch below solves
the issue. ref_field_type is referenced in scaleforsame_y and needs to be set earlier in
ff_vc1_pred_mv to have the desired effect.

 libavcodec/vc1_pred.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

Comments

Carl Eugen Hoyos April 21, 2018, 7:50 p.m. UTC | #1 
2018-04-21 21:05 GMT+02:00, Jerome Borsboom <jerome.borsboom@carpalis.nl>:
>> Fixes #2557.
>>
>> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>> ---
>>  libavcodec/vc1_pred.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/libavcodec/vc1_pred.c b/libavcodec/vc1_pred.c
>> index 54712f6b7a..9f42a930fe 100644
>> --- a/libavcodec/vc1_pred.c
>> +++ b/libavcodec/vc1_pred.c
>> @@ -98,9 +98,9 @@ static av_always_inline int scaleforsame_y(VC1Context
>> *v, int i, int n /* MV */,
>>      }
>>
>>      if (v->cur_field_type && !v->ref_field_type[dir])
>> -        return av_clip(scaledvalue, -v->range_y / 2 + 1, v->range_y / 2);
>> +        return av_clip(scaledvalue, -v->range_y / 2 - 1, v->range_y / 2);
>>      else
>> -        return av_clip(scaledvalue, -v->range_y / 2, v->range_y / 2 - 1);
>> +        return av_clip(scaledvalue, -v->range_y / 2, v->range_y / 2 + 1);
>>  }
>>
>>  static av_always_inline int scaleforopp_x(VC1Context *v, int n /* MV */)
>> --
>> 2.11.0
>
> scaleforsame_y references ref_field_type. Therefore, it needs to be set
> before scaleforsame is called.

Please mention ticket #2557 in the commit message.

> Signed-off-by: Jerome Borsboom <jerome.borsboom@carpalis.nl>
> ---
> I am not sure your patch is correct. The existing implementation agrees with
> VC-1 spec.
> See Figure 119 in 10.3.5.4.3.4.2 in particular. Please have a look if the
> patch below solves
> the issue. ref_field_type is referenced in scaleforsame_y and needs to be
> set earlier in
> ff_vc1_pred_mv to have the desired effect.

This patch also fixes the issue for the given sample

Carl Eugen
diff mbox

Patch

diff --git a/libavcodec/vc1_pred.c b/libavcodec/vc1_pred.c
index 54712f6b7a..3a52a22bc6 100644
--- a/libavcodec/vc1_pred.c
+++ b/libavcodec/vc1_pred.c
@@ -341,6 +341,8 @@  void ff_vc1_pred_mv(VC1Context *v, int n, int dmv_x, int dmv_y,
     } else
         opposite = 0;
     if (opposite) {
+        v->mv_f[dir][xy + v->blocks_off] = 1;
+        v->ref_field_type[dir] = !v->cur_field_type;
         if (a_valid && !a_f) {
             field_predA[0] = scaleforopp(v, field_predA[0], 0, dir);
             field_predA[1] = scaleforopp(v, field_predA[1], 1, dir);
@@ -353,9 +355,9 @@  void ff_vc1_pred_mv(VC1Context *v, int n, int dmv_x, int dmv_y,
             field_predC[0] = scaleforopp(v, field_predC[0], 0, dir);
             field_predC[1] = scaleforopp(v, field_predC[1], 1, dir);
         }
-        v->mv_f[dir][xy + v->blocks_off] = 1;
-        v->ref_field_type[dir] = !v->cur_field_type;
     } else {
+        v->mv_f[dir][xy + v->blocks_off] = 0;
+        v->ref_field_type[dir] = v->cur_field_type;
         if (a_valid && a_f) {
             field_predA[0] = scaleforsame(v, n, field_predA[0], 0, dir);
             field_predA[1] = scaleforsame(v, n, field_predA[1], 1, dir);
@@ -368,8 +370,6 @@  void ff_vc1_pred_mv(VC1Context *v, int n, int dmv_x, int dmv_y,
             field_predC[0] = scaleforsame(v, n, field_predC[0], 0, dir);
             field_predC[1] = scaleforsame(v, n, field_predC[1], 1, dir);
         }
-        v->mv_f[dir][xy + v->blocks_off] = 0;
-        v->ref_field_type[dir] = v->cur_field_type;
     }
 
     if (a_valid) {