[mythtv] Why Not MPEG-2 Encoding?

Geoffrey Hausheer mythtv0368 at phracturedblue.com
Mon Dec 5 17:35:33 UTC 2005


Kevin Kuphal wrote:
> > Perhaps I should have said:real-time MPEG-2 encoding isn't possible
> > *in Myth* with software encoding capture cards.  I know nothing of the
> > technical details of why this is the case.
Actually, everything exists in Myth to do it already.  You could just
use libavformat/libavcodec, and get reasonable results.  Not sure
about performance, but if your machine has the horsepower, there is no
reason this can't be done.  My recomendation would be to use libreplex
(which is part of mythtranscode now).  With all my work trying to get
valid MPEG2 streams from the transcoder, I had a nightmare trying to
get libavformat to generate high-quality streams (basically, it didn't
do rate limiting correctly).  I don't know if I have a bttv card lying
around anymore, and I'm certain I won't have enough time to play with
it for a while, but if noone takes up the cause for a month or so, I
may look into it.  I already have all the parts needed in the
transcoder, they'd just need to be moved into libmythtv.

Note, that the return-on-investment for something like this is pretty
low.  It is likely you won't have enough left-over horsepower to do
any filtering or enable any of the high-quality settings.  A pvrx50
will likely do a better job more reliably, and for the $70 or so they
cost, it's almost certainly the way to go if you need MPEG2 (which,
like you, I do for my Roku media player)

.Geoff


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