[mythtv-users] Multiple cards with different audio sample rates
lynchmv at gmail.com
Sat Jun 3 01:17:24 UTC 2006
On 6/2/06, Michael T. Dean <mtdean at thirdcontact.com> wrote:
> On 06/02/2006 03:55 PM, Michael Lynch wrote:
> > On 6/2/06, Michael T. Dean <mtdean at thirdcontact.com> wrote:
> >> On 06/02/06 00:09, Michael Lynch wrote:
> >>> The bttv card needs to have a sample rate of 48000 or the audio gets
> >>> terrible (humming) and the saa713x card needs to have a sample rate of
> >>> 32000. Herein lies my problem. With the audio sample rate set to
> >>> 48000 for the 'Live TV' recording profile, the bttv audio is perfect,
> >>> but the saa713x audio turns to chipmunks. If it change the 'Live TV'
> >>> audio sample rate to 32000 to accomodate the saa713x card, the bttv
> >>> card begins to hum.
> >> http://www.mythtv.org/wiki/index.php/DigitalSoundHowTo#Setting_up_ALSA.27s_.asoundrc.2C_Properly
> >> Fix that and you can play back the 32kHz audio without problems.
> > Does it matter if I'm not using the digital out?
> Yes, the ALSA configuration file matters if you're not using digital
> out. Or, no, it makes no difference whether you're using digital or
> analog out--without a proper ALSA configuration some streams won't play
> properly on your sound card. (Wasn't sure which question you were
> asking. :)
> Some sound cards ("software" sound cards) offload a lot of audio
> processing to the CPU. For example, the much-touted NVIDIA nForce
> SoundStorm APU is really just a pretty nice audio driver with some basic
> hardware support. Your card is one of these.
> Fortunately, ALSA means that we have a pretty nice audio driver for
> /all/ sound cards--even those with bad Windows drivers.
> > The above question aside...if I understand the wiki page correctly, I
> > can pretty much drop in that config file with minor changes.
> > I need to verify the device number for the "analog-hw" and/or
> > "digital-hw" virtual devices, and change them accordingly in the
> > config. Running aplay -l gives me card 0 with device 0 as ICH5 and
> > card 0 with device 4 as ICH5-IEC958. That being said after I change
> > the settings in the config file should I change anything else?
> > Reading on the alsa-project web page it states that the
> > .asound/asound.conf files "allow extra functionality, such as routing
> > and sample-rate conversion, through the alsa-lib layer" - I'm guessing
> > this is how the captured audio gets 'fixed' so that my playback is
> > good no matter what.
> > If I'm missing the whole point, please let me know.
> Exactly right. By my reading, you have to change one place in the
> .asoundrc--the digital-hw device should be 4. (Although, if you never
> use digital output, it won't really matter if you don't change it.)
> Then, either specify a default audio device in the ALSA configuration
> file as appropriate (the first section of the file--which currently
> specifies mixed-analog as the default), or tell Myth to use
> "ALSA:analog" or "ALSA:mixed-analog" with the mixer device "default" and
> everything will work.
> mythtv-users mailing list
> mythtv-users at mythtv.org
OK, I have set up myth to use ALSA:mixed-analog and set the mixer to
default. The Live TV recording profile specifies a sample rate of
32000 and if I understand this correctly /etc/asound.conf as listed
earlier should be doing a coversion to 48000. If I am incorrect in
that understanding please let me know.
The playback for the bttv card still gets a hum to it during live tv
but the saa7134 card sounds fine (there is more to the saa7134 card
audio, but that's for another thread). When I change the 'Live TV'
profile to a sample rate of 48000 the bttv card loses its' hum but the
saa7134 card once again sounds like chipmunks.
I seem to be getting somewhere as myth is accepting the fact that I
have an ALSA:mixed-analog 'device'. Now I think I just need to get my
sample rates corrected in the right places. Thanks for all of the
help so far and any more is welcomed...
More information about the mythtv-users