Live TV only - Audio stutters when NPVR receives H.264 transcoded stream

[craigrs84]

I don't watch a lot of live TV so this is not a major problem for me, but if I do attempt to watch live TV the audio stutters badly and it's unwatchable.

I have a transcoding HDHomerun which is sending a H.264 stream to NPVR. If I disable transcoding then the audio sounds fine.

I thought maybe it was a audio decoder issue but I don't think so anymore, I've tried both Lav and AC3Filter with the same results and my PC has plenty of remaining CPU and RAM.

The audio works fine if I watch Live TV with transcoding enabled in XBMC or in HDHomerun's QuickTV app so the problem seems localized to NPVR.

Anyways I just wanted to report the potential issue so that you are aware of it.

Thanks.

[Reddwarf]

If tou don't have a graphic card able to decode H.264 then your cpu has to do it, and that may be just a little bit too heavy for the cpu so the audio decoding suffere. What graphic card are you running, and what windows version?

[Zeb]

In NPVR Settings -> Decoders, try setting MPEG1 Audio to Disabled. The decoder settings you use in NPVR have no bearing on XBMC.

[Reddwarf]

In NPVR Settings -> Decoders, try setting MPEG1 Audio to Disabled. The decoder settings you use in NPVR have no bearing on XBMC.

If his graphic card does not decode h.264 in HW it will still load the cpu in XBMC too.

[Zeb]

He isn't complaining about the video in either app, just the audio in NPVR.

[Edit] And only with live TV, not playback. Here's an old thread: http://forums.nextpvr.com/showthread.php...lter-Graph

[johnsonx42]

in config.xml, set <ForcedLiveTVClock>AC3 Audio Renderer</ForcedLiveTVClock> in the <Renderers> section.

[mvallevand]

QAM mpeg2 is ac3 audio though, This is always the trouble, without logs everyone tries to guess.

Martin

[Reddwarf]

Martin is right that we need more information, but what I'm saying is that is the cpu is very busy decoding video tha audio will suffer, I'v seen this when I'v run npvr on single core and weak cpu systems.

[Zeb]

A hardware issue would probably affect playback, since the TS the same. We are hampered in our speculations by not owning a transcoding HDHomeRun, but if it performs a 2-channel downmix on the AC3, then the issue comes as no surprise to me. I've seen the same issue in MPEG2 watching MeTV, where the AC3 is 2-channel to begin with. I have actually used the config.xml setting suggested by johnsonx42 above ever since the year-old thread that I posted a link to above. Disabling MPEG1 in NPVR is just a little easier to implement and reverse. If you sometimes use NPVR to play files with MPEG1 audio, then the config.xml setting is the best solution - unless of course I'm completely wrong about the problem. The live TV buffer might also be worth a look.

[craigrs84]

Apologize for the delay replying back - disabling MPEG1 audio corrected the problem. Thanks for the suggestions! Sorry Zeb, I think I you suggested this already in my thread about decoders but I overlooked it and forgot about it.

EDIT: modifying config.xml as suggested by johnsonx42 also solved the problem.

So setting <ForcedLiveTVClock>AC3 Audio Renderer</ForcedLiveTVClock>value in config.xml means MPEG1 audio won't work in live tv but will work when playing back a previously saved file? Is that correct?

Thanks.