[mythtv-users] Yet another sound problem
Kevin Kuphal
kuphal at dls.net
Thu Jul 8 17:33:44 EDT 2004
David Wadler wrote:
> A few months ago, I set up Myth on my machine (2.4.x kernel on
> Gentoo) and had lots of issues with sound. Ultimately, I fixed it by
> loading the tvmixer module. I don't know why that fixed it, but as
> soon as I loaded the module and restarted mythfrontend, everything
> sounded good.
>
> I had to wipe my drive (don't ask) and am now running a 2.6.6 kernel.
> The new kernel made it very easy to get ALSA up-and-running and I'm
> using it in Xine, mplayer, XMMS, and other apps. However, when I set
> Myth to use ALSA:default, I got choppy video (lots of prebuffering
> messages) and audio that wasn't quite right. It sounds clipped. I
> played with the mixer levels, and no matter how low I go, there
> remains distortion. I switched to /dev/dsp and /dev/adsp, both of
> which work, but both of which have the same audio distortion. In
> addition to adjusting the levels with my soundcard, I also tried to
> adjust the TV-Card's mixer, by doing alsamixer -c 1. I can only
> adjust the level attached to "Capture" and changing it doesn't have
> any effect.
>
> ALSA gives me great sound in my other apps and I'm fairly confident
> that I have it set up correctly. I don't know what I'm missing in
> Myth. I'd be okay with using OSS with Myth, provided I can get clean
> sound. Any ideas?
>
> Loaded modules:
>
> Module Size Used by
> snd_pcm_oss 48932 2
> snd_mixer_oss 17344 1 snd_pcm_oss
> tvmixer 4720 1
> snd_bt87x 11204 0
> tuner 17356 0
> tvaudio 20428 0
> tda7432 6924 0
> bttv 143980 2
> video_buf 16516 1 bttv
> i2c_algo_bit 8904 1 bttv
> btcx_risc 3848 1 bttv
> i2c_core 18756 6
> tvmixer,tuner,tvaudio,tda7432,bttv,i2c_algo_bit
> snd_via82xx 22208 2
> snd_pcm 84580 3 snd_pcm_oss,snd_bt87x,snd_via82xx
> snd_timer 20996 1 snd_pcm
> snd_ac97_codec 61444 1 snd_via82xx
> snd_page_alloc 8964 3 snd_bt87x,snd_via82xx,snd_pcm
> snd_mpu401_uart 6144 1 snd_via82xx
> snd_rawmidi 20128 1 snd_mpu401_uart
> snd_seq_device 6536 1 snd_rawmidi
> snd 46564 10
> snd_pcm_oss,snd_mixer_oss,snd_bt87x,snd_via82xx,snd_pcm,snd_timer,snd_ac97_codec,snd_mpu401_uart,snd_rawmidi,snd_seq_device
>
> Thanks,
> David
What kind of audio hardware are you running and what kind of capture
card? Are you using a soundcard with the audio from your capture card
going to the line-in on your soundcard? Judging from the tvaudio being
loaded I guess you are pulling the sound directly from your capture
card. I recently had a problem with btaudio and solved it (crossing
fingers) by using the ALSA bt87x driver instead of btaudio. Perhaps if
you loaded that to pull sound from your card you might have better luck.
BTW, the native ALSA support in Myth is not ready for primetime so for
sure you should use OSS emulation on /dev/adsp. I've tried to put
together some patches to improve the ALSA support but they're a work in
progress still and not in CVS yet.
Kevin
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