[mythtv-users] BT848 Volume control?

[papenfuss at juneau.me.vt.edu]

	I've got some oddball BT848 card that had the same problem.  What I 
found out is that the mythbackend is hardcoded to max out the volume if it's 
lower than a threshold.  After a bunch of snooping around, I found (on line 
899 on mythtv-0.13/mythtv-0.13/libs/libmythtv/NuppelVideoRecorder.cpp):

        if ((volume == -1 && va.volume < 32768) || volume != -1)
        {
            if (volume == -1)
                va.volume = 65535;            // no more silence 8-)
            else
                va.volume = volume;
            if (!quiet)
                fprintf(stderr, "audio volume set to '%d'\n", va.volume);

	It's NOT a mixer setting.  It's a parameter on the v4l device, which
you can change with the v4lctl command.  Something like 'v4lctl volume 33000'
*before* mythtv loads up should set it above the threshold.  If that works (try
'v4lctl list' after setting the volume without mythtv running), you're in
business.  I've got it in a script that fires up mythtv.  If it is doing what 
you want (volume >32768) but still clips, change that line in the code 
to be something less.

	That little issue is what pushed me over the edge to compile it all 
from source.  Turns out	33000 makes it not clip for me so I didn't need to 
compile it anyway.  Oh well... wasn't *that* bad (except for >1Hr compile time 
on a dual Celeron 300/450).

YMMV,
-Cory

 On Mon, 12 Jan 2004, Thor Johnson wrote:

> Semi-obvious question:
> 
> Is there a volume control on the BT848 type cards (I have a Avermedia TV
> Studio Pro)?
> 
> On network channels, Myth is beautiful, but on off-network channels like FX,
> or especially Speed Channel, the capture card puts out too much signal, and
> I get clipping, which gets encoded to MP3 to create a horrid
> surround-channel noise...
> 
> Just trying to see if I can get away without adding pots to the line...
> 
> TIA,
> Thor Johnson
> 
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