[mythtv-users] XvMC profile group playing MPEG4 videos?

Paul Bender pebender at san.rr.com
Wed Mar 19 17:19:07 UTC 2008


Johnny Russ wrote:
> Paul Bender wrote:
>> Johnny Russ wrote:
>>   
>>> I have an old PIII 1GHz box that I use to playback SD shows and also my 
>>> kids' videos. In 0.20 I used XvMC to playback my MPEG-2 shows and the 
>>> default settings (whatever they were) on the internal player worked fine 
>>> with my MPEG-4 videos. Since updating to 0.21 I haven't been able to get 
>>> my playback profile setup such that I can playback my MPEG-2 shows and 
>>> my MPEG-4 videos satisfactorily. With my hardware I can play the videos 
>>> with ffmpeg, but using this for my TV shows starts to get a little jumpy 
>>> if anything is going on (e.g. commercial flagging). However, if I use 
>>> XvMC my TV shows are great with minimal CPU usage, but my MPEG-4 videos 
>>> have issues (hanging, audio sync, choppy). I thought that XvMC would 
>>> only be used for MPEG-2 streams 
>>> (http://www.mythtv.org/wiki/index.php/Playback_profiles)? I set up my 
>>> playback profile such that XvMC would be used first, then ffmpeg would 
>>> be used second. I thought this would cause my MPEG-2 shows to use XvMC 
>>> and then everything else would use ffmpeg. However, with this setup my 
>>> videos have issues. If I remove the XvMC or change the order of the 
>>> profile groups then the videos are fine. It seems to me like my MPEG-4 
>>> videos are using the XvMC profile group instead of falling through to 
>>> the ffmpeg profile group. Am I mistaken about XvMC will only play MPEG-2 
>>> content? Since the content all has similar resolutions, I can't make 
>>> distinctions based on that criteria. Any ideas what is going on? Is 
>>> there a way to use XvMC for only my TV shows and not for my videos?
>>>     
>> I believe that the issue is how the profiles are used. My understanding 
>> is that once it determines that the hardware supports the decoder and 
>> renderer for the specific video size, it uses it. However, if the codec 
>> does not support the selection it falls back to another selection 
>> without consulting the profile.
>>
>> In your case, when it finds that it cannot use the xvmc-blit renderer to 
>> play MPEG4, it fall back to the xv-opengl renderer. If this is your 
>> problem, then you will see messages in console output from mythfrontend. 
>> Therefore, if you run mythfrontend in a terminal window, then you will 
>> see messages say that xvmc-blit is not supported by the codec and that 
>> it is using xv-opengl instead.
>>
>> For MiniMyth, I created a patch so that xvmc-blit falls back to xv-blit 
>> (if present) and xvmc-opengl falls back to xv-opengl (if present).
>>
>> There is a ticket (#4792) about this.
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>>   
> Thanks for the feedback. I am using precompiled packages. The standard 
> decoder works good enough on most occasions so I think I will just rough 
> it until a fix trickles down my way. Or maybe I will finally have some 
> leverage to convince my wife to let me upgrade my hardware :-). I read 
> over ticket #4792. I liked two of your suggestions. It would be nice if 
> the profiles were consulted on a codec failure. That is how I understood 
> the profiles to work anyway. I also liked the idea of letting the 
> profiles be conditioned on more criteria like codec, container, etc. 
> That would make it very easy to ensure that your content was being 
> rendered with the ideal settings. Thanks again for the help.

The suggested options are Steve's not mine. I agree that extending the 
profiles would be the best option. However, as I was patching the stable 
release, I was trying to be minimally invasive. In addition, it was easier.


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