[mythtv-users] ffmpeg vs vdpau decode for h264

[Tom Dexter]

On 5/17/19, Tom Dexter <digitalaudiorock at gmail.com> wrote:
> On 5/15/19, Tom Dexter <digitalaudiorock at gmail.com> wrote:
>> What would cause MythTV to use ffmpeg decoding as apposed to vdpau
>> when playing back h264 video? A followup question to that: Is there
>> any reason this would be happening more with version 30.0 than with
>> 29.1? It cound be coincidence but I seem to be running into that more.
>> I know there were changes related to h265, but I'm not aware of
>> anything around h264.
>>
>> Thanks!
>> Tom
>>
> Interesting. I was able to determine based on some of my older
> frontend logs, that what I'm running into here are the same vdpau
> decode errors reported here, which are causing the mythtv to revert to
> software decoding:
>
> https://code.mythtv.org/trac/ticket/13223
>
> It sounds as though that all started after one of the ffmpeg version
> bumps(?). I see that 29.1 used ffmpeg 3.2, and that issue seemed to be
> related to 3.4, and version 30.0 appears to have version 4. It also
> looks like there were major changes in avformatdecoder.cpp all the way
> around.
>
> I found one small example of a video where mythtv reverts to software
> decoding due to those errors, yet xine on my system (Gentoo
> media-libs/xine-lib-1.2.9-r2 and media-video/ffmpeg-3.4.5) plays this
> using vdpau decoding just fine. It's sample #7 under the "3 Codecs,
> Framerates and Subtitles" here:
>
> https://kodi.wiki/view/Samples
>
> That is this file:
> https://drive.google.com/file/d/0BwxFVkl63-lEbVptTVZ2NENURHM/view?usp=sharing
>
> I'd be interested to see if others find the same behavior. Most
> importantly, I'd love to see if someone running 29.1 and using vdpau
> can play this in mythtv with vdpau decoding.
>
> Thanks!
> Tom
>

I meant to mention: If anyone tests that, if you're not already aware,
the quickest way to determine what decoding is in use while playing
the video is in the menu at Playback -> Playback Data. The Codec/Dec
there will show for example "H264 vdpau" or "H264 ffmpeg".

Tom