[mythtv-users] nuvexport and ffmpeg-CVS

Chris Petersen lists at forevermore.net
Sun Dec 18 02:48:19 EST 2005

> Further tests seems to suggest that using --transcode
> with a single pass and no noise reduction gives virtually
> identical picture quality as transcode with multi-pass and
> noise reduction.

Contrary to what most people think, the only REAL advantage to multipass 
is that it provides a consistent (nearly guaranteed) output file size, 
and the best possible quality for that size.  Single pass can have 
awesome quality, but if you were to tweak things such that the single 
pass produced a file of the same size as the two-pass file, the two-pass 
one might look slightly better because it would have had a smarter 
"insight" into which frames should be encoded at a higher bitrate, and 
which ones didn't matter (eg. black frame) and could be encoded lower.

> The run time on that is 1h 28 minutes (still twice ffmpeg's time)
> and it plays perfectly in xine, mplayer, kaffeine, vlc. and
> Windows Media Player 9 and later.  It shows
> slight jerkyness in Winamp and Windows DivX Player
> (older version).

Really strange.  In all of my tests, ffmpeg and transcode (with noise 
reduction enabled) were almost exactly the same speed (about 6 fps for 
me).  I put up with the slowness, though, since whenever I've tried to 
use ffmpeg the output is full of artifacts.

> Now if I can just get the command line to work so
> I can run these nuvexport jobs from the backend I'll be happy.

/etc/nuvexportrc plus:

nuvexport --transcode --require_cutlist --mode xvid --title some_title

personally, I wouldn't trust it, though.  Too many things can go wrong. 
  You might also want to add the --force_mythtranscode option since I've 
seen transcode freak out with some ivtv recordings.


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