[mythtv-users] Preserving HDTV AC3 audio stream whilst transcoding

[Isaac Richards]

On Thursday 18 November 2004 12:22 am, Kyle Rose wrote:
> Stephen Hocking <shocking at houston.rr.com> writes:
> > Just out of curiousity, what speed CPU are you using, and what video
> > card? I'm trying all this with an AMD XP 2400+ and a Nvidia FX5200.
>
> Pentium4 3.2, same video.
>
> > There's also a post on the devel list refering to some work done by other
> > people on a fast MPEG2 decoding algorithm. They were able to get 62fps
> > from a 720p stream on a 933MHz P3 with a Geforce 2 MX440. If we could
> > do something similar with the MythTV MPEG2 decoder, I suspect that a
> > lot of my problems would go away. Even using the pcHDTV people's Xine
> > tweaks (which I think use the XvMC Nvidia specific extension) would be
> > a big help.
>
> I use simple Xv, not XvMC, and still see > 50% CPU usage on HT this
> processor.
>
> Just replacing the myth engine with whatever xine uses would drop CPU
> usage by at least 30%.  I don't know why myth is so slow; whenever I
> bring this up, Isaac either ignores it or just says it's the same code
> and refuses to admit there's a problem.

Xine and myth use identical amounts of cpu on my xp1800+ when using Xv -- ie, 
around 75% (and X using around 20% for both) when decoding 1080i.  Both play 
back mostly smoothly, with a glitch every 10 seconds or so (ie, the CPU is 
very marginal for what it's doing).   If you're seeing a difference, you have 
a configuration issue.  What that may be, I don't know, since you've not done 
much besides whine.

Isaac