[mythtv] Alsa capture support

Matthew Wire devel at mrwire.co.uk
Mon Aug 21 14:42:02 UTC 2006

> Wouldn't saa7134-alsa work with ALSA's OSS emulation (i.e. instead of 
> using an OSS audio driver module, use an ALSA audio driver module, but 
> enable ALSA's OSS emulation)?  If so, doing so does not ignore your 
> requirements ("I'd like to do it properly") since the API used by the 
> application is largely irrelevant (unless you need access to features 
> not available in one API--and Myth doesn't).
It should do shouldn't it.  In fact my oss emulation provides me
with /dev/dsp1 for this purpose - except it doesn't work :(
When I use myth to capture from /dev/dsp1 I get nothing, capturing
from /dev/dsp (with a loopback cable) also gives nothing or static -
I've read reports on the internet that myth does not correctly unmute
saa7134 based cards but I've been unable to test this (and I don't have
v4lctl to test this with).
Using tvtime I always get sound from the loopback correctly.  I've also
been able to test the saa7134-alsa module by executing 
"arecord -D hw:1,0 -r 32000 -c 2 -f s16_LE | aplay - " which allows me
to hear sound correctly.
So, I figured if mythtv supported alsa capture my problems would be
solved and it will also allow others to use alsa without oss which seems
cleaner to me!

I've been looking through the code and found audio capture code in
I think this is the only place audio is captured so effectively I should
only have to modify this file (plus configuration stuff).  Is that
What I will probably do is write a patch to replace oss support
initially, then when I get that working put oss back in and add some

Matthew Wire

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