Mythtv, odd speeding up and stopping?

lugoteehalt · 07-07-2009, 11:04 AM

Just installed Mythtv on Debian Lenny 500 kernel 2.6.29. With live TV it gives high pitched speeded up sound for about 2 seconds, then stops, then repeats this indefinitely. It say:

Code:

2009-07-06 07:06:11.216 WriteAudio: buffer underrun
2009-07-06 07:06:11.382 NVP: prebuffering pause
2009-07-06 07:06:11.384 WriteAudio: buffer underrun
2009-07-06 07:06:12.563 WriteAudio: buffer underrun
2009-07-06 07:06:12.704 NVP: prebuffering pause
2009-07-06 07:06:12.705 WriteAudio: buffer underrun

over and over. Or laterly:

Code:

OSD Theme Dimensions W: 640 H: 480
2009-07-07 03:58:39.576 TV: Changing from None to WatchingLiveTV
2009-07-07 03:58:39.578 Realtime priority would require SUID as root.
2009-07-07 03:58:39.680 Video timing method: USleep with busy wait
2009-07-07 03:58:40.746 NVP: prebuffering pause
2009-07-07 03:58:42.016 NVP: prebuffering pause
2009-07-07 03:58:43.012 NVP: prebuffering pause
2009-07-07 03:58:44.095 NVP: prebuffering pause
2009-07-07 03:58:45.381 NVP: prebuffering pause
2009-07-07 03:58:46.481 NVP: prebuffering pause
2009-07-07 03:58:47.535 NVP: prebuffering pause
2009-07-07 03:58:48.439 NVP: prebuffering pause
2009-07-07 03:58:49.545 NVP: prebuffering pause
2009-07-07 03:58:50.585 NVP: prebuffering pause
2009-07-07 03:58:51.660 NVP: prebuffering pause
2009-07-07 03:58:52.743 NVP: prebuffering pause
2009-07-07 03:58:53.647 NVP: prebuffering pause
2009-07-07 03:58:54.687 NVP: prebuffering pause
2009-07-07 03:58:55.959 NVP: prebuffering pause
2009-07-07 03:58:57.291 NVP: prebuffering pause
2009-07-07 03:58:58.307 NVP: prebuffering pause
2009-07-07 03:58:59.642 NVP: prebuffering pause
2009-07-07 03:59:00.978 NVP: prebuffering pause

If the recording it makes automatically is played the whole thing is speeded up, but without the pauses. Trying to slow this down dissapears the sound - i.e. Mickey Mouse on helium or nothing.

If it is configured so that there is no sound then the TV picture is quite normal.

It only seems to give sound if the capture card is configured in Mythtv's mythtv-configure to use /dev/dsp1.

Possibly relevant error messages:

Code:

2009-07-07 03:58:39.091 NVR(/dev/video0): Unknown video codec.  Please go into the TV Settings, Recording Profiles and setup the four 'Software Encoders' profiles.  Assuming RTjpeg for now.
2009-07-07 03:58:39.091 NVR(/dev/video0) Error: Unknown audio codec
2009-07-07 03:58:39.097 AutoExpire: CalcParams(): Max required Free Space: 2.0 GB w/freq: 15 min
ioctl VIDIOC_G_FMT: Invalid argumen

Have no idea how to fix this nothing seems to work. Thanks any help.

pljvaldez · 07-07-2009, 12:49 PM

What type of capture card do you have? Is it analog TV or digital? Have you setup the tuners and encoding profiles?

The last error message seems like maybe your machine is using software encoders, in which case, how much RAM do you have?

lugoteehalt · 07-08-2009, 11:50 AM

Thanks.

Quote:

Originally Posted by pljvaldez

What type of capture card do you have? Is it analog TV or digital? Have you setup the tuners and encoding profiles?

The last error message seems like maybe your machine is using software encoders, in which case, how much do you have?

4GB of RAM.

PEAK DVB-T Digital TV Hybrid PCI Card 138508AGPK it is both analog and digital.

"Have you setup the tuners and encoding profiles?" Err....Told it about the capture card. Have not done anything about encoding as far as I know. If you could give me some idea how to do this it would be nice??

pljvaldez · 07-08-2009, 12:15 PM

It appears to me that card doesn't do hardware encoding, which means your CPU and RAM have to do the encoding on the fly. If this machine serves as both the backend and frontend, it has to first encode the video and then decode the video.

Here is a page listing some performance optimizations. You may also try modifying the transcoding settings for each recording profile (EP, LP, SP, etc). Your best bet may be to change each recording profile to "No Encoding" (which might be the same as SP, I forget and am not in front of my Myth box right now). That should lower the overhead on both ends, but will take up more hard disk space.

lugoteehalt · 07-09-2009, 12:41 PM

The problem is - rereading my post it may be unclear - the sound is high pitched, mickey mousey, and the picture+sound stops every second or so. Then it restarts and the cycle repeats.

Have got it to stop stopping by slowing the time stretch:

Quote:

mythfrontend -> utilities/setup -> tv settings -> playback groups -> time stretch (=75)

But it is still high pitched, but picture reasonable speed and does not keep stopping (though there is something slightly wierd about it).

Could not work out how to do your thing with the "No Encoding" but did suceed in pixelating the picture to great crudeness, with 1/2 cm pixels - so does this prove it is not a problem of processing speed? It is only sort of 15% mythbackend 5%mythfrontend 7% X at worst sort of thing, according to 'top'.

Is it a sound problem, perhaps?

Thanks again.

lugoteehalt · 07-11-2009, 04:41 AM

For the record solved the problem with:

Frontend > setup > audio [output device: /dev/dsp; passthrough: default; Stereo; Passive; check 'use internal volume controls'; mixer: /dev/mixer1; mixer controls: pcm]

It is an saa7143 capture card so set the audio rate to 32000 as one is ?instructed, even though this is not its rate. Using the alsa OSS emulation module.

Picture too noisy, ?fault of hardware.