[vlc-devel] [PATCH] Fixed incorrect backward/forward reference ordering in vaapi deinterlacing

Victorien Le Couviour--Tuffet victorien.lecouviour.tuffet at gmail.com
Tue Jun 27 15:25:42 CEST 2017

On Tue, Jun 27, 2017 at 03:58:48PM +0300, Oliver Collyer wrote:
> After testing the Motion Adaptive deinterlacing mode and finding it produced lots of flicker/judder and not much deinterlacing I traced the error back to the below.
> Although it seems a little counter-intuitive, the "forward_refs" are actually the frames older than the current one, and the "backward_refs" are those later.
> In addition, the forward_refs (previously the backward_refs) have to be ordered such that [0] is most recent, [1] older, etc; before this patch it was the opposite.
> Just to be 100% sure, I have also cross-referenced this approach with how FFmpeg does it:
> https://github.com/FFmpeg/FFmpeg/blob/master/libavfilter/vf_deinterlace_vaapi.c <https://github.com/FFmpeg/FFmpeg/blob/master/libavfilter/vf_deinterlace_vaapi.c>
> See function deint_vaapi_filter_frame.

Oh thanks I would have never guessed that. It is indeed a bit
counter-intuitive. And obviously the VA documentation does not tell you that.
I was probably not able to see those flicker/judder by myself as on my computer
I only have one backward frame. Anyway, thanks again.
Also, LGTM.


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