[mythtv-users] Occasional metallic sound when recording

Eloy A. Paris peloy at chapus.net
Wed Oct 22 19:48:30 EDT 2003


"Joseph A. Caputo" <jcaputo1 at comcast.net> writes:

> I also have a CS46xx-based sound card with ALSA drivers, and have
> experienced something similar regarding the 'tinny' sound.

Oh, I am glad I am not the only one :-)

> Mostly I've noticed that if another process has the sound card open
> when I fire up either the frontend or the backend, then I get the
> metallic sound on either playback or record, respectively.

Interesting. This is a possibility, since I am running Gnome all the
time, and I have it configured for sound effects, so The Enlightened
Sound daemon (esd) is always running.

> To correct the situation I have to restart the Myth process after
> closing the 3rd program.

Well, as I mentioned in my post to alsa-devel, I found that a good
workaround (if a recording was taking place and you could not interrupt
it) was to run alsamixer and press the space bar twice while on the ADC
control. The first space bar hit cancels capturing and the second
re-enables it. After this operation the metallic sounds goes away.

If I am watching live TV, the solution is just to press the Escape key
to go back to the menu and then enter again in "Watch TV". Next time I
enter audio will be fine.

> Note that my soundcard (and probably yours, too) supports multiple
> simultaneous opens, so if another process has the sound card open it
> doesn't necessarily hang Myth as happens with other sound cards when
> people, for instance, forget to disable aRTs.

Right, our cards support hardware mixing.

> I don't know if it's a driver issue or a hardware issue, but I'll bet
> if you make sure nothing else is accessing your dsp device when you
> start Myth (or probably more accurately, before Myth does an 'open' on
> the device (like when starting a recording, playback or MythMusic
> session)), you'll probably see this problem disappear.

Ok, I'll try that. I'll make sure I log out from Gnome and leave the
server parked in a console. Nothing is touching /dev/dsp when I am not
using Gnome.

The other test I can do is to just turn off esd while in Gnome. If I
watch TV, 1 out of 10 times I'll have the metallic noise. So doing this
should be a good way of testing your theory. I'll do this and report
back.

Thanks,

Eloy.-


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