[Vorbis] bitrate limits don't work with -q settings?

[Sander Sweers]

Well, I can not reproduce this behaviour in Linux.

I am using oggenc "OggEnc v1.0.1 (libvorbis 1.0.1)"

oggenc -q3 03.\ Unknown\ Quantity.flac

Opening with flac module: FLAC file reader
Encoding "03. Unknown Quantity.flac" to "03. Unknown Quantity.ogg" at
quality 3.00
        [ 99.7%] [ 0m00s remaining] \

Done encoding file "03. Unknown Quantity.ogg"

        File length:  4m 37.0s
        Elapsed time: 0m 34.5s
        Rate:         8.0478
        Average bitrate: 126.4 kb/s

-----------------------------------------------
oggenc -q3 -m 96 03.\ Unknown\  Quantity.flac

Enabling bitrate management engine
Opening with flac module: FLAC file reader
Encoding "03. Unknown Quantity.flac" to "03. Unknown Quantity.ogg" at
quality level 3.00 using constrained VBR (min 96 kbps, no max)
        [ 99.7%] [ 0m00s remaining] \

Done encoding file "03. Unknown Quantity.ogg"

        File length:  4m 37.0s
        Elapsed time: 1m 35.5s
        Rate:         2.9087
        Average bitrate: 126.4 kb/s

For me the bitrate does not drop under 96kbit when using -q3. I have
not  experienced any problems with my iriver H120 yet.

Maybe you should move to Linux ;-) Seriously though, get the official
binary encoder from the Xiph site and see if this problem still
exists.

I did however see a drop in performance when limiting the minimum
bitrate to 96k. Is this because of the different engine being used?

Sander


On Wed, 29 Dec 2004 14:25:43 -0500, Nic Watson <nic at ghs.com> wrote:
> Thanks for the quick response.  To get versioning out of the way, I
> recompiled the libraries and oggenc from mainline svn yesterday night.
> I see the same results.
> 
> Unfortunately, I am stuck on a stupid transport.  On the IRiver players,
> any time the bitrate dips below 96kbps, you'll hear a click or pop, and
> the song will usually end.  -q3 -m 96 doesn't work.  Is there any way to
> use VBR and absolutely guarantee that the bitrate won't fall below a
> certain level?  I figured that's what the bitrate_hard_min option was
> for, but it seems to have the opposite effect.
> 
> Nic
> 
> Ralph Giles wrote:
> 
> > On Tue, Dec 28, 2004 at 10:23:50PM -0500, Nic Watson wrote:
> >
> >
> >>The problem I'm seeing is that oggenc's VBR encoding doesn't seem to pay
> >>attention to any sort of bitrate limitation, either the -m or
> >>bitrate_hard_min settings.  It isn't that it temporarily dips below the
> >>minimum; the average for the whole (in this case, easily compressible)
> >>file is 10-20% too low.
> >
> >
> > Are you complaining that the encoder does too good a job? :-)
> >
> > The managed bitrate modes use a different engine from the standard
> > constant-quality engine, and is mutually exclusive with -q. You have
> > to turn it on with -b or in more recent versions of oggenc with
> > --managed.
> >
> >
> >>I see roughly the same results on an old 1.0.1 version of oggenc as well
> >>as a new vorbis 1.1-linked one I found on rarewares.org.
> >
> >
> > The managed bitrate handling was changed in the 1.1 release; I don't
> > know if the rarewares oggenc is the updated version from svn or not, so
> > it may be using the same logic as the 1.0.1 version.
> >
> > If it's underruns you're worried about you probably shouldn't be using a
> > managed mode; -q will do a better job. You really only need this if
> > you're on some stupid transport that really can't handle the normal vbr
> > streams.
> >
> >  -r
> >
> _______________________________________________
> Vorbis mailing list
> Vorbis at xiph.org
> http://lists.xiph.org/mailman/listinfo/vorbis
> 


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