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

[Paul B Mahol]

On 4/21/18, Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:
> 2018-04-21 10:22 GMT+02:00, Paul B Mahol <onemda at gmail.com>:
>> 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);
>
> Makes the affected frames bit-exact, so lgtm.

This probably needs no + 1 and - 1 part, so will commit without it.