[mythtv-users] Normalizing audio?

[Tom Lichti]

On 3/3/06, Sasha Z <kleptophobiac at gmail.com <http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users>> wrote:
>/ My two tuners have differing audio levels. Each channel has its own
/>/ audio level. The whole thing is a pain because I'm constantly
/>/ twiddling the volume control across huge ranges and blasting myself
/>/ every now and then.
/>/
/>/ Would it be possible to have myth autocalibrate itself by listening to
/>/ each channel for a few minutes during non recording time, and then
/>/ figuring out an offset to send to the card during recording so that
/>/ all recordings have at least somewhat similar volumes...? My
/>/ television does this auto audio gain control very nicely, and it's
/>/ very cool. PBS doesn't blast the crap out of me, and FOX isn't so
/>/ quiet that I have to go to 100% volume.
/>/ _______________________________________________
/
I too agree that it would be nice to have that. Ideally I'd like to see at least a per card volume setting, if not per channel. What I just tested was to run 

ivtvctl -Y -d /dev/video0

to get the current audio settings, which shows:

ioctl: VIDIOC_QUERYCTRL
Brightness = 127
Contrast = 63
Saturation = 63
Hue = 0
Volume = 58880
Mute = 0

The max volume setting is supposed to be 65525 according to the documentation, so I started a recording and then set it:

ivtvctl -y volume=65535 -d /dev/video0


and it did increase:

ioctl: VIDIOC_QUERYCTRL
Brightness = 127
Contrast = 63
Saturation = 63
Hue = 0
Volume = 65024
Mute = 0

Not to 65535 but close. I then watched the video, and the volume did 
increase when I changed the setting. I guess I could have done it on 
live tv (I just did, works there too) so it is possible to somewhat 
normalize the volumes via that method, so it also should be possible via 
MythTV. I took a very brief look at the code and didn't see anything 
obvious, but I'm going to dive in a little deeper and see what I can 
find. This would make my life a bit easier, since my two 250's are much 
louder than my 150.

Tom