[mythtv] Editor step forward by keyframe needs 2 keyclicks with nvdec in UK SD recordings

[Mark Kendall]

On Thu, 20 Feb 2020 at 09:50, Mark Kendall <mark.kendall at gmail.com> wrote:
> > nVdec with h264 is still giving decoding artefacts with static pictures,

As mentioned previously, this appears to be an issue with NVDEC as I
see the same problem on all of the other players that support NVDEC.

> > and with mpeg2video the smaller steps in the editor are often not as
> > expected.  It looks as if the most recent commits are for vaapi.
>
> I spent some time testing editing, single frame seeks etc yesterday on
> various machines. As far as I can tell, with the latest fix to the
> VAAPI deinterlacers, the behaviour is consistent across software
> decode with any deinterlacer (CPU and GLSL), VDPAU and VAAPI.
>
> NVDEC is the problem. There is a small issue, as you noted, of the
> first forward seek not being seen on screen, which should be fixable
> and is a result of the changes I made to handle stream changes. The
> bigger issue is that when NVDEC deinterlacing is enabled, short
> backwards seeks are totally innacurate. This is an issue with how we
> handle the increased framerate seen when NVDEC does the deinterlacing.
> I'm considering switching to use the cuda-yadif deinterlacing filter -
> which will eliminate the framerate issue in most cases and give us
> full control of deinterlacing. Currently we can only enable NVDEC when
> the decoder is opened.

I forgot to mention - switching off 'Prefer driver deinterlacers'
should switch it to shader deinterlacing which should also avoid the
worst of the problems. Didn't think to test this yesterday.

regards
Mark