[vorbis] Are there low bitrate "Voice" plans

[Geoff Shang]

Hi all:

I was about to bring up the subject of low bit-rate vorbis anyway, but I
see someone's beaten me to it.  The description of the vorbis codec on the
front of vorbis.org states that it is a codec for 44.1khz and 48.0 khz
audio at 16 bits or more, ranging between 16kbps and 128kbps *per
channel*.  Those in the know will realise that 1.0beta2 already goes beyond
this with the capability of 175kbps per channel in mode 6 encoding.  Now,
16kbps per channel means a minimum stereo rate of 32kbps.  Of course, voice
and even low bit-rate audio in general does not have to be 44.1khz.  Are
there plans to implement lower sampling rates for lower bit rates,
e.g. 32khz or 22.05khz for 16kbps stereo, for example?

I ask this because I've gotten involved in a new internet broadcasting
initiative called ACB Radio Interactive (http://www.acbradio.org) and we're
realising the limitations of low bit-rate MP3.  The arguments between mono
or stereo are strong, meaning that people are prepared to sacrifice quality
for stereo.  I personally would rather 22khz mono over 11khz stereo anyday,
but being a modem user, I am limited to uploading 20kbps anyway, which
limits my options to 11khz mono or stereo.  I am very excited at the
potential of vorbis to improve this situation, but I am curious as to
whether people who must operate at rates below 32kbps will be limited to
mono or not?  Having had a few rare opportunitites to hear 56kbps 22khz
stereo MP3 streams, I'd settle for that if that were all there was.

Finally, to bring it back to the realm of voice encoding, I recall that the
LAME encoder has an experimental voice mode.  Whilst it is not brilliant,
it is a noticeable improvement (IMHO) on the normal quality delivered by
low bit-rate MP3.  Perhaps this algorythm may be of some use to the vorbis
project.

Geoff.


-- 
Geoff Shang <gshang10 at scu.edu.au>
ICQ number 43634701

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