No sound on LiveTV

[MSH-0]

Hi!

I revently upgraded my setup from Mythbuntu 12.04 to 14.04. I have this funny problem with sound on LiveTV. Otherwise sound works ok, on videos, music etc. Behavior is like this:

- Start LiveTV, picture is ok. Sometimes there is also sound, but as soon as the overlay information bars disappear, so goes the sound.
- Sound is there during delay, when changing channels but disappears as soon as the new channel is dialed

It looks like as if the frontend is unable to correctly select the audio stream inside the multiplex. Anyone else have this problem? Using Using Mythbuntu 14.04.1, Asus M3N78-EM motherboard w/ GeForce 8300 IGP and Hauppauge WinTV Nova TD500 2x dual DVB-T tuner.

[splurben]

Have you tried selecting an audio track while on LiveTV? Press M and go into the audio section and see what's there?

Also, after an upgrade, I'd definitely go into Setup - Audio and see which audio device is selected. Are you using analogue or HDMI audio?

[MSH-0]

I have tried selecting different audio tracks, but it doesn't help. I also did some tests with different audio setups. I had audio device ALSA:hdmi:CARD=NVidia,Dev=0 selected, but experimented a bit with different setting. So far best results were ALSA:pulse, but still it worked only couple of times with LiveTV. I'm using HDMI-audio.

[blm-ubunet]

Long shot but maybe when you record you have setup some transcoding or filtering of some audio tracks.
Is it possible your LiveTV "recordings" have different audio tracks?
You can find the liveTV recordings (before deletion) in same places as other recordings.
Can probe test with mediainfo or mythffmpeg.

The audio ELD reporting etc on the first video cards/IGP that supported HDMI output was incomplete.
Then alsa/pulse reports the incorrect audio capabilities of the attached device etc.

There is a very good (only) linux alsa HDMI audio doc available from nVidia that lists all the odd/weird behaviour to be expected of the different generations.
ftp or http://http.download.nvidia.com/XFree86 ... audio.html

I believe your IGP8300 is an[b] MCP78[/b].

You could try to limit the audio to stereo only (2ch PCM) as an expt.
Then add AC3 as pass-thru'.
I think the early nVidia IGP supported 8 ch discrete over HDMI. Check the nVidia HDMI doc .

[MSH-0]

I did some testing... watched TV, no sound on TV/Amp except if I reselected the same channel. Then sound was there for short while until OSD disappeared. Copied files created to my laptop and played them on VLC-player and sound was there. So the backend should be working ok, but there is something funny with frontend LiveTV and/or HDMI sound.

I also tried to force audio output to HDMI, using 2ch mode and AC3 pass-thru, but result is still the same. I'll try to dig into it some more when I have more time to concentrate into it...

[blm-ubunet]

Try setting the audio sync (OSD) back to zero & then exit FE & restart.

Really need to look into the log files for FE & BE during the audio cut-out.

Do you have any old legacy/deprecated VDPAU settings in the "Video filters" ?
Need Log files.

[MSH-0]

Doesn't seem to help... I tailed some logs, they are attached to this post.

As fas as I know, there are no outdated VDPAU-settings. I created new ones on top of preset values. However, I'm not sure is deinterlacing is really working as it should be.

[blm-ubunet]

Your FE log shows one deprecated VDPAU filter (colorspace); this is now a OSD GUI setting.
Studio levels also moved to GUI setting.
Not meant to use vdpaubuffers setting except in extreme circumstances.

Your BE log shows the LiveTV channel (program) is looking for PIDs that are missing in the multiplex stream.
You need to re-scan existing transports (& manually update/insert).
This problem can occur with channels that are only broadcasting for limited hours (in a day).

Running "mythtv-setup -v chanscan,siparser" & redirecting stdout into file can be very informative.

[MSH-0]

Did couple changes... I don't know why it tried to invoke colospace because custom filter properties have not been defined. However, I added vdpaucolorspace=0 to custom filter and now there are no errors in mythfrontend.log. Sound is still missing though. Also tried disabling vdpau and usinx ffmpeg/xvideo but with no effect to sound.

Errors in backend log were there because our antenna had been repositioned and re-scan had not been done at that point, so couple of channels were missing because of that. I did the re-scan and updated those channels.

[blm-ubunet]

The default vdpau filter is "vdpaucolorspace=auto".
You could try VDPAU slim (that's all your h/w can do) & check you have allocated the max system memory (>=512MB) to the on-board chipset GPU (if possible in BIOS).

You can play the offending recordings (with sound) using mythffmpeg ?

[MSH-0]

Ok, got some time to debug again...

Tried VDPAU Slim, result is the same. IGP has been allocated max memory of 512MB.

I started to watch TV, without sound again and let it be for while. Then copied the file to videos-directory and played it again using internal player and it worked flawlessly, with sound. So this is strictly isolated to Live TV for some very odd reason.

Edit: Just moment ago I applied some OC to GPU and still there's no sound when switching Live TV on, but now sound was there and at least seamed stable when changing channels. I'll have to look into it some more to confirm this though. Previously I have encountered some breaks in sound if using too heavy deinterlacing for GPU to handle, so it might be a glitch on how 14.04.1 and/or nVidia driver is using resources.

[blm-ubunet]

Is this not just a case of liveTV (trying) following too close to real-time ?
The classic soln was to try pausing playback for 2 seconds & continue..

I find the default buffering/delay-to-wall-clock to cause a unsatisfactory result.

[MSH-0]

Well yes it is! Tried pausing and playing again and sound worked without problems from there. I have never seen such thing before (been using mythbuntu since 2009)... Is there a place in frontend UI to set buffering/delay or is it in some config file?

[blm-ubunet]

No easy user adjustment that I know of..
I haven't bothered to find a programmatic soln yet because liveTV has a bad interaction with some patches I'm not willing to drop.