[mythtv-commits] Ticket #897: RealTek ALC880 Issues (Audio Buffer Overflow)

MythTV mythtv at cvs.mythtv.org
Fri Dec 30 08:03:00 EST 2005


#897: RealTek ALC880 Issues (Audio Buffer Overflow)
----------------------------------+-----------------------------------------
 Reporter:  ian.bonham at gmail.com  |       Owner:  ijr
     Type:  patch                 |      Status:  new
 Priority:  major                 |   Milestone:     
Component:  mythtv                |     Version:     
 Severity:  medium                |  
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 Hi Robert,

 Just a quick note you may want to include mate, as I have had this problem
 and spent hours on it. I was unable to find anything on the web about it,
 so the cure was trial and error (for my setup anyway), and it seems it's a
 growing problem.

 I have an MSI mobo, 915 series, with a P43.2ghz and 512gb Ram. When I
 tried to play or record live TV I had major issues with stuttering video
 and choppy sound. This was in Myth0.18.1 on Debian (KnoppMyth) Kernel
 2.6.13.2-chw-3 #1 SMP. I was able to recreate the issue using cat
 /dev/video0 > ./test.mpg, so I knew it wasn't down to Myth as the stream
 dump (from a Hauppauge PVR150) was knackered as well. However, Myth was
 outputting bugs of "Prebuffering Pause" and "Audio Buffer Overflow,Audio
 Data Lost!". It seems a lot of people are having the same prob.
 It seems it was the sound so upgraded to Alsa1.0.11rc1, which reportedly
 solved a lot of the ALC880 problems. Still the same tho, so I downloaded
 RealTek's driver from their site. Still the same.

 So I started to look at OSS. Reading their Doc's it states their driver
 works with all AC97 chipsets. This made me think, in the BIOS there is an
 option to switch the onboard sound between Disabled/AC97/Azalia. I checked
 my BIOS and it was in Azalia mode. I switched it back to AC97, then
 brought Debian up and ran alsaconf again just to check any settings were
 reset.

 MythTV and recording now works perfectly. It seems there is a bug
 somewhere in the ALSA drivers for the Azalia mode of the ALC880. Running
 it in AC97 mode means alsa can talk perfectly to it. This simple fix
 suddenly got Myth working perfectly and I'm really impressed with it. Glad
 I wiped M$'s MCE now! It's worth noting that I didn't try the OSS drivers
 in the end. As of today (30/12/05) it's still noted on OSS docs as
 experimental, and as alsa runs nicely with AC97 mode I didn't bother
 opening the OSS can of worms!

 Hope that helps someone else out, dunno if you want to stick it in the
 docs somewhere, but a simple BIOS tweak saved my buying an SB Live! :)

 Happy New Year to all the Myth team, thanks for a great project,

 Bon

-- 
Ticket URL: <http://cvs.mythtv.org/trac/ticket/897>
MythTV <http://www.mythtv.org/>
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