[mythtv-users] AVerMedia M150-D (CX88 blackbird) audio problem: FIXED!

Rod Smith mythtv at rodsbooks.com
Sat Mar 24 19:26:18 UTC 2007

Hi all,

Some time ago I posted about a problem I'd been having with an AVerMedia 
AVerTV M150-D MPEG-2 board that I bought cheap on eBay: It worked fine most 
(about 2/3) of the time, but the rest of the time it produced "razzy" audio, 
as if the soundtrack were being piped through a kazzoo. I have, I think, 
fixed the problem, so I thought I'd share the solution. To understand this, 
you should first know that I've never heard the distorted audio when using 
mplayer to play a video stream. Even if MythTV produced bad sound in live TV, 
if I exited from live TV and started mplayer on the device, the sound was 
fine. Going back to MythTV sometimes produced bad audio but sometimes didn't. 
This made me think that the problem had to do with the way MythTV was tuning 
the device -- perhaps in timing issues, attempting to access the device 
before the new channel had been fully tuned.

To work around this problem, I simply created a script that tunes the card 
using v4lctl and referred to that script as an external tuning command in 
mythtv-setup. Here's the script I'm using:

v4lctl -c /dev/video1 setchannel $1
v4lctl -c /dev/video1 volume mute off
#sleep 1

I've included the second call to v4lctl because the card's volume comes up 
muted when the drivers load, so this is a way to ensure that I get sound. I 
initially included a "sleep" call to ensure that the card had enough time 
to "settle," but it doesn't seem to be necessary, so I've commented it out. 
It's conceivable that calling v4lctl directly from MythTV would work as well 
as calling it in a separate script, but I've not tested that.

Prior to implementing this fix, the card was unreliable at channel-surfing; 
the MythTV frontend would sometimes hang. Now it hangs all the time when 
channel-surfing. Thus, this fix is useless if you want to channel-surf with 
the card. I haven't yet tested back-to-back recordings to see how they'd be 
impacted by this change.

I've edited my wiki entry on this board to provide information on this 


I hope somebody else on the list will find this information useful.

Rod Smith

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