[FFmpeg-devel] [PATCH] avcodec/vc1: fix B predictor validity for 4-MV MBs

[Carl Eugen Hoyos]

2019-01-14 9:05 GMT+01:00, Jerome Borsboom <jerome.borsboom at carpalis.nl>:
> The B predictor for 4-MV MBs in interlace field pictures is not used
> for blocks 0 and 2 when the picture is 1 MB wide.
>
> Signed-off-by: Jerome Borsboom <jerome.borsboom at carpalis.nl>
> ---
> My 'shuffle calculation of MV predictor candidates' patch overlooked the
> corner case of 1 MB wide field interlace pictures. According to VC-1 spec
> and the reference decoder, the B predictor is not used for for block 0 and
> block 2 when the picture is 1 MB wide. This patch corrects this.
>
>  libavcodec/vc1_pred.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/libavcodec/vc1_pred.c b/libavcodec/vc1_pred.c
> index e1758a3817..77dda86cd0 100644
> --- a/libavcodec/vc1_pred.c
> +++ b/libavcodec/vc1_pred.c
> @@ -289,6 +289,8 @@ void ff_vc1_pred_mv(VC1Context *v, int n, int dmv_x, int
> dmv_y,
>          case 3:
>              off = -1;
>          }
> +        if (v->field_mode && s->mb_width == 1)
> +            b_valid = b_valid && c_valid;

I will push this if you don't request commit rights
but shouldn't this be "b_valid &= c_valid;"?

Carl Eugen