[mythtv-users] Sound problems when using TV functions

[David Wadler]

Hello Fellow Mythees,

Last week, I posted about having grainy, delayed audio while watching LiveTV.  BJM offered me a very prompt response, but -- hothead that I am -- I had already wiped by box clean and cursed Fedora. :-)  I'm back up with Gentoo and have Myth up-and-running.  Video quality is substantially better than it was after my first attempt and I'll continue to try and tweak it.  There are some lingering issues with MythVideo, but they are relatively minor and I'll post another time if I can't resolve them on my own.  The audio problems, however, continue to rear their ugly heads.

Some background:
Running Gentoo 2.4.25 kernel on an Athlon XP 2400+.  Using onboard sound (Via) and have a BT878 tv-card.  The TV card's line out goes to my onboard line-in.
AlsaMixer settings:  AUX set to CAPTUR and muted; Capture set to CAPTUR with volume 80%.
Running KDE (no difference in quality whether artsd is running or not).  I am NOT using btaudio (maybe I should?).
Relevant modules loaded:

snd-pcm-oss            39524   0
snd-mixer-oss          13944   0  [snd-pcm-oss]
snd-via82xx            14112   0  (autoclean)
snd-pcm                63908   0  (autoclean) [snd-pcm-oss snd-via82xx]
snd-ac97-codec         49980   0  (autoclean) [snd-via82xx]
snd-page-alloc          6772   0  (autoclean) [snd-via82xx snd-pcm]
snd-mpu401-uart         3856   0  (autoclean) [snd-via82xx]
snd-rawmidi            14592   0  (autoclean) [snd-mpu401-uart]
snd-seq-oss            30368   0  (unused)
snd-seq-midi-event      3584   0  [snd-seq-oss]
snd-seq                39344   2  [snd-seq-oss snd-seq-midi-event]
snd-timer              15748   0  [snd-pcm snd-seq]
snd-seq-device          4336   0  [snd-rawmidi snd-seq-oss snd-seq]
snd                    34532   0  [snd-pcm-oss snd-mixer-oss snd-via82xx snd-pcm
 snd-ac97-codec snd-mpu401-uart snd-rawmidi snd-seq-oss snd-seq-midi-event snd-s
eq snd-timer snd-seq-device]
tuner                  10696   1  (autoclean)
tvaudio                14152   2  (autoclean)
tda7432                 4104   1  (autoclean)
bttv                   95904   0
soundcore               4036   6  [snd bttv]


Problem:
Watching Live TV or recording TV is near impossible because the sound is terrible.  It's grainy, clipped, and speech is difficult to comprehend.  Everything is in sync though -- which I guess is a good thing.  Also, Myth has ALSA support (I did an ldd as you suggested and came up with the following:  libasound.so.2 => /usr/lib/libasound.so.2 (0x40ca4000)), but I can only select between /dev/dsp and /dev/adsp when selecting sound options.  Furthermore, when I run mythfrontend, it states the following:

2004-05-12 15:32:25 Connecting to backend server: 127.0.0.1:6543 (try 1 of 5)
2004-05-12 15:32:26 Opening OSS audio device '/dev/dsp'.
2004-05-12 15:32:26 Using XV port 78

OSS?  I want ALSA -- or at least I thought I did.  I just want intelligible sound. :-)

Other sound oddities that may yield clues:
ALSA Mixer settings don't automatically restore themselves even though I do an alsactl store.  I don't know why this is the case.  It also seems like different applications play at different volumes; while I'm aware that some apps have their own volume controls, I don't think that's the problem.  For example, I aplay and alsaplayer play at a much lower volume than MythTV is I start them up without any config changes.  I suspect it's because one the first two are using ALSA while Myth is using OSS.

Outside of TV-related stuff, sound is excellent.  There is no way that the TV card would have sound that would be THIS bad, so I suspect I'm not doing something correctly.

Suggestions, advice, guidance, tricks, tidbits, and the like are both welcome and greatly appreciated.

David
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