[mythtv] Re: [Fwd: Re: [mythtv-users] Your soundcard is not reporting free space correctly.]

Ann Patterson annp322 at sbcglobal.net
Tue Mar 9 22:32:54 EST 2004

On Mon, 2004-03-08 at 08:15, Ann Patterson wrote:
> -----Forwarded Message-----
> > From: Ann Patterson <annp322 at sbcglobal.net>
> > To: Discussion about mythtv <mythtv-users at mythtv.org>
> > Subject: Re: [mythtv-users] Your soundcard is not reporting free space correctly.
> > Date: Tue, 02 Mar 2004 08:02:03 -0800
> > 
> > On Sun, 2004-02-22 at 19:51, Ann Patterson wrote:
> > > I have had a myth box set up and working nicely for some time, using
> > > myth 0.14, FC1, and Jarod's instructions. Today, I put a new sound card
> > > into the box, a M-Audio Revolution 7.1 (ice1724 alsa driver). I have
> > > alsa installed, and except for mythtv, the new sound card works fine.
> > > Mythmusic, mplayer, and everything else I've tried is fine. But when I
> > > try to either watch live tv, or play recordings that I recorded before I
> > > put the new card in, I get no sound at all, and the following error
> > > repeatedly from the frontend:
> > > 
> > > Your soundcard is not reporting free space correctly. 
> > > Falling back to old method...
> > > 
> > <snip>
> > 
> > I'll respond to my own post. After doing some debugging, it turns out
> > that, indeed, my soundcard is *not* reporting free space correctly.
> > Mplayer and Xine work because both use a different method than myth for
> > syncing video and sound. The alsa folks are looking at it now. I'll post
> > again when it's fixed. 
> After even more debugging, and a reading of the OSS docs, I discovered
> that the values returned from ioctl(audio_fd, SNDCTL_DSP_GETOSPACE,
> &info) are undefined if you're not writing full fragments to the card.
> For every other card I tested, the values returned from this call were
> fine, even when writing partial fragments. But when I ran this with the
> M-Audio card, the values are all over the place. I was able to duplicate
> the problem with the alsa osstest program, writing blocks of 1000 bytes.
> When I changed the osstest program to write 4096 bytes (this card's
> fragsize), the problem went away.
> Ann P.

Here's a patch that sets the fragment size on the card to a reasonable
value, then writes the audio in full fragments. It fixes the problems
I'm having with the M-Audio card. I don't think it should hurt anything

Ann P.
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