[vorbis] Re: Quality problem reencoding

[Dan Nelson]

In the last episode (Nov 15), Greg Wooledge said:
> Dan Nelson (dnelson at allantgroup.com) wrote:
> > I guess the problem might be oggenc's option parser, then.  Given a
> > stereo 22050hz input file, I can't seem to get oggenc to encode less
> > than 22kbits.  The lowest bitrate it will allow on the commandline (for
> > 22050hz/2ch input) is -b 30, but if you also add -M 1, it will generate
> > a file with an average bitrate of 22.
> 
> $ sox -V War\ -\ Low\ Rider.wav -r 22050 foo.wav
> [...]
> sox: Finished writing Wave file, 17102568 data bytes 8551284 samples
> 
> $ oggenc -b 16 -M 16 --downmix foo.wav foo.ogg 
[...]
> at average bitrate 16 kbps (no min, max 16 kbps), 
> using full bitrate management engine
> Done encoding file "foo.ogg"
>         Average bitrate: 15.7 kb/s
> 
> Of course, the resulting file sounds pretty bad.  (It's actually not
> as bad as I expected it to be, but it has horrible artifacts in the
> mid-range frequencies, and the high frequencies are gone.  A lowpass
> might help a bit.)
> 
> Are you sure you're using Vorbis 1.0?

Yes, but I was using stereo 22Khz input.  With mono, oggenc lets you
use -b 16, which on my test wav actually generated an avg 24kbit file. 
I had to add -M 16 to force it to generate an avg 16kbit file.  Is
there an oggenc flag that does what lame's --abr ## flag does?  i.e. "I
want an output file with this average bitrate".  So far -b consistently
gives me a bitrate up to 50% higher than what I asked for.

Time to move this thread to a vorbis list?   Oh wait.  I see the CC. 
Nevermind :)


-- 
	Dan Nelson
	dnelson at allantgroup.com
--- >8 ----
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