[mythtv-users] Audio Crackle / Nvidia Acceleration

George Nassas gnassas at mac.com
Sat Nov 3 15:06:11 UTC 2012

On 2012-11-03, at 10:44 AM, Ken Mandelberg wrote:

> I'm used to running the frontend on an older Intel Core2 box with Intel GMA graphics, which works reasonably well with evidence of performance lag on fast forward and other intensive video motion.
> I just tried running the frontend on a slightly newer Core2 box with Nvidia graphics. I expected to see a difference and don't. Do I need to do something special to get the benefit of Nvida acceleration? The frontend is built from the trunk and VDPAU is enabled in the build.
> The other issue is I'm getting audio crackle on the newer box. The audio used SPIDF in either case to the same amplifier, and the older box had no crackle. I notice the older box used

I'm running a similar setup (oldish core2, initially intel graphics but switched to nvidia, audio to an external processor via spdif) so it can work and in fact does work quite well.

Besides the nvidia drivers being active, which you said you have, make sure myth is using the vdpau playback profile. From memory those profiles are found at the frontend's Setup -> Playback -> Video or something like that.

> I do have the extra audio buffering enabled, and the crackle is worse without it. Any ideas about the audio?

Not sure about the crackling but I believe JYA posted something a while back about the extra buffering being unnecessary. Nowadays the frontend will dynamically ask for extra buffering at the device level if it needs it. To get things going my startup does a preemptive "echo 128 > /proc/asound/card0/pcm1p/sub0/prealloc" as root.

- George

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