[mythtv-users] newbie audio problems

Stephen Mathezer mathezer at yahoo.com
Sun Jun 15 22:34:41 EDT 2003


* Craig Longman <craigl at begeek.com> [030615 21:03]:
> Stephen Mathezer wrote:
> 
> >I'm relatively new to mythtv, I have things sort of working but am
> >having trouble with audio quality.
> >
> >I'm running 0.9.1 on Debian with a 2.4.20 kernel and alsa 0.9.4. I have
> >a Gigabyte 7VAXP which has VIA 8235 sound built in.  My capture card is
> >a WinTV GO.
> >
> >With some screwing around I have managed to get btaudio to work with
> >analog output on /dev/dsp2. I am able to watch live tv and record. Sound
> >quality is however pretty poor no matter what I try.  There is a fair
> >bit of hissing and crackling all the time.
> >
> >If I run xawtv and do the "sox -r 480000 -c 1 -t ossdsp /dev/dsp2 -t
> >ossdsp /dev/dsp" thing then sound quality is vastly better. My question
> >is, how do I set the sample rate that high in MythTV for both live
> >watching and recording? I tried actually setting the samplerate to
> >480000 in the codecparams table manually but that caused backend
> >crashes.  If I run sox all the time, then I am getting sound output all
> >the time which also isn't good.
> >
> do you mean 48 000 here?  as opposed to 480 000 like  you wrote.
> 

Nope, I do mean 480000.  I got that from
http://lloyd.dyndns.org/index.php?MythTV%20Page by following the links
to the btaudio stuff:

http://lloyd.dyndns.org/index.php?Btaudio%20installation

It may be that I am SOL with this particular capture card and btaudio
unless I use sox to resample. For what it is worth, sox actually tells
me that the rate it ends up using is 192000.

> >I've searched through the mailing list which did help me get btaudio
> >going, but I couldn't find any solutions to the poor quality sound.
> >
> >Can anyone help me out with this?
> >
> i've heard that with btaudio you need to set 32K as the sample rate.  i 
> understood that this was all btaudio could handle, but it sounds like 
> you get it to work with higher raters, so maybe its something other than 
> btaudio that prevents >32K.
> 
> cheers,
> 
>    CraigL->Thx();
> 

I have no idea on that one. I have found btaudio rather difficult to
figure out.

So, I guess my choices are
-use sox to resample, I will play with this.
-record using the little loopback cable from my WinTV going to line in
(what to I set the record device to for this? /dev/dsp0?)
-get another card. If it costs a little bit more money to make this
work, then so be it.  What does everyone else use?  All I need is a
capture card, I have a separte video card with TV out.

thanks for any suggestions

-Steve



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