[mythtv] Current state of MythTv using Via XvMC VLD Hardware MPEG decoding

[Terry Barnaby]

Andrew Wilson wrote:
> I'm seeing a lot of problems on audio using XVMC. I'm using 0.18, and
> the description below applies to that. CVS of about a week ago (last
> time I tried it) was unusable as the audio was awful.
> 
> When I turn off XVMC VLD hardware decoder, the M10k can't keep up.
> However, I found that if I turn off deinterlacing then it can keep up
> OK.. ~12% idle. Nearly all audio problems go away with this setup, and
> I'm tempted just to leave it at this setting as it's perfectly
> watchable.
> 
> I'd much rather use xvmc though, mainly because I can slow the M10k
> down to 600MHz and reduce the temperatures and fan speeds to an
> acceptable level. It's also just wrong not to use the hardware
> decoding when I've paid for it :-)
> 
> The audio problem I'm hearing is hard to describe. It sounds like
> during each small chunk of audio, perhaps 250 millisecs, some
> fragments are being repeated 2 or 3 times and others omitted.
> 
> Does this square with what other folks are seeing? 
> 
> Is there anything I can usefully do to help in debugging this stuff?
> I'd be more that glad to help.
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I suspect that this is because MythTv has not been compiled
with MMX support. The changes recently made to MythTv's configuration
system has changed the way CPU's are recognised/setup. I have
found a similar problem to yours if MMX is not enabled.

I use a configuration line of:
configure --prefix=/usr --enable-xvmc-vld --cpu=i686 --enable-dvb-eit 
--enable-dvb --dvb-path=/data/src/MythTv/include; qmake mythtv.pro

Also there are major Audio/Video sync problems when XvMC VLD
is used on certain channels that contain multiple Audio channels.
You have to set "HW Decoder" for each of your DVB-T capture cards to
work around this bug.

Note that I ma using MythTV CVS date 2005-04-23. Versions after that
date do have probems due to the fact that the new Xv/XvMC merge code
has not stabalised yet.

Terry