Choppy Audio Due to Possible Incorrect Filter Graph

[Zeb]

I receive MeTV as an SD QAM channel, its single audio track being "Track 1 [AC3, eng]." Nevertheless, I found that I got choppy audio if I enabled any MPEG1 Audio decoder (which I don't need personally, having no analog channels; I'm just investigating the issue reported by PVRDon). I'm using AC3Filter ver. 1.63b. In AC3Filter Properties, I tried unchecking MPEG Audio on the Systems tab, but that did not solve the issue. I then made the config change suggested earlier by johnsonx42: <ForcedLiveTVClock>AC3 Audio Renderer</ForcedLiveTVClock> I was careful to restart NPVR Service after editing config. That setting appears to have solved the choppy audio issue in my case, so perhaps PVRDon was too hasty in testing that setting. However I don't have WinTV installed, so perhaps there is also some conflict between AC3Filter and the Hauppauge decoders that PVRDon is using.

So what's unique about the audio on MeTV and a few other channels that PVRDon gets? Although muxed as AC3, I suspect that MeTV's audio is 2-channel, but have no way of testing that myself. For one thing, MeTV is devoted to reruns from the analog era, so any six-channel audio track would be an upconverted fabrication. Probably most North American members get that channel in one form or another.

[mvallevand]

It wouldn't work. The audio bitstream has to be "packed" before it can be output via HDMI/SPDIF (and yes I did try writing a filter that did just that.. passing it through that is). Otherwise, we would have had bitstreamed HD audio on day one.

Even with WSAPI?

Martin

[whurlston]

I never considered trying WASAPI. If I get the spare time, I might try that.

[Zeb]

Assuming you have no Surround Sound system, is there an easy way to determine whether a TV channel's AC3 stream is 2-channel or 6-channel, or whether it has other peculiarities? If one of you knows the answer, would you please check MeTV's AC3 stream, assuming you get that channel? It doesn't seem to matter whether it's via ATSC or QAM.

[mvallevand]

LAV and ffshow have tray icons that show you the format, not sure about ac3filter.

Martin

[mulletback]

It's 2-channel for me (ATSC).

[Zeb]

Thank you mulletback! I suspect that's also the case with other channels that caused PVRDon to post this thread.

[Edit] Found the AC3Filter setting to show tray icon, and my QAM version of MeTV is also 2-channel.

[PVRDon]

As many have suggested, AC3Filter does not appear to be the source of my problem.

So, please disregard that statement. I did, however, say "apparently" when talking about the uninstall of the AC3Filter software.

After struggling through previous versions of GB-PVR, two different Hauppauge tuners, and WinTV, I thought I sort of knew what I was doing with NextPVR and HDHomeRun.

I guess not.

If I figure out what is going on, I will come back and let everyone know.

Thanks again to those who made comments and otherwise tried to help.

Donald

[hoborg]

Hi.
Did you tryed to globally change your decoders (SAF) ?
Link below

[imilne]

It'll be interesting to see if other users with this problem see the problem go away if they uninstall AC3Filter. It'd be odd but you never know.

I wish

For me - with both mpeg and ac3 audio channels - I need to use ac3filter because it can encode the 2 channel (stereo/pro logic) mpeg to 2.0 dolby digital, which means I can leave Windows set to 5.1 audio and bitstream everything to my amp. If I just send the audio as-is, then the amp thinks it's getting 5.1 (when it's not really) so it doesn't apply any pro logic decoding and you're left with voices coming out the left/right speakers instead of the centre. Conversely, if I set Windows to 2 channel, then NPVR will still happily bitstream stuff, but programs like TotalMediaTheatre stupidly decide to not allow bitstreaming because it then thinks it's not running on a 5.1 setup.

I haven't checked for a while, but I seem to recall disabling the ac3 encoded option in ac3filter did reduce any stuttering significantly, but maybe not completely. I also find the stuttering worse on some channels than others; mainly the ones I don't watch thankfully. And the pause/resume and/or skip back trick always eliminates it completely.

Iain