Speeds up and stops repeatedly, mythtv?

[lugoteehalt]

Mythtv on Debian Lenny 500. Just installed.

High pitched fast speach when watching TV. Then after about 2 seconds it stops - freezes picture and sound, then it goes through the cycle again indefinitely.

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

and more recently:

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 there is no sound due to the way it's been configured then the TV picture plays correctly.

If the recording it always makes is played it just goes fast, a la Benny Hill, but without the pauses. Slowing this down dissapears the sound.

It only gives sound sound if mythtv-setup puts the capture card to /dev/dsp1.

Possibly relevant?:

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

Nothing seems to effect it. Thanks any help.

[paulkoan]

The prebuffering pause is likely to be the cause of it all, and I have found that it is usually a network speed issue - is this a separate frontend / backend?

If not, what else is the box doing, could it be taxed in some way that it prevents it decoding?

When a recording completes, do you have it set to transcode down to something smaller? If so, once this is completed, do you still see the issues?

[lugoteehalt]

The prebuffering pause is likely to be the cause of it all, and I have found that it is usually a network speed issue - is this a separate frontend / backend?

If not, what else is the box doing, could it be taxed in some way that it prevents it decoding?

When a recording completes, do you have it set to transcode down to something smaller? If so, once this is completed, do you still see the issues?

Great thanks.

1/ No the frontend / backend are on the same computer.

2/ top says, typically 20% backend 5% frontend 10%X sort of thing. The picture is all right as long as there's no sound. Totally unfamiliar with Mythtv but I did get it to pixilate the picture into a very crude state with 1/2 cm. pixels - it cannot cause to much load like this can it? - problem was unchanged Dual core AMD 64bit, 4GB RAM.

I've found a way to stop it keeping stopping - mythfrontend -> utilities/setup -> tv settings -> playback groups -> time stretch (=75) (i.e. slow it down a bit) still high pitched sound but picture reasonable speed and does not keep stopping But perhaps slightly jerky.

3/ Sorry have no idea what this means.

For what it's worth I'm wondering if it's a sound problem but am completely unable to work out how to tell it the codec to use. Better still a list of things to use for sound that could just be tried one after the other.

[paulkoan]

Ok, perhaps it is the playback profile - what do you have in TV Settings / Playback / Playback Profiles (3/9)?

I am using ffmpeg + xvideo

[lugoteehalt]

Thanks that's right I think. Have got it to work with:

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

At least I think that's what did it.

Picture a bit noisy though.