[vorbis-dev] Encoding 8KHz audio (voice)

[Gregory Maxwell]

On Tue, Aug 14, 2001 at 11:33:02AM -0400, Paul McHale wrote:
> Is there support for encoding/compressing 8KHz sampled speech?  Am I heading
> in the right direction with Vorbis?  I have heard results with 44KHz audio
> and am quite impressed.  As always, any help appreciated.

For speech, you can do much better compression if you understand that you
are encoding speech and code accordingly. Look at GSM, or the celp codecs.

Vorbis will probably never do as well as these special purpose codecs in
pure voice applications, but it's possible that we may see a voice codec in
ogg in the future.

Of course, you can run speech through Vorbis today, and providing you are
using a sample rate that tuned modes are available for (44.1/48KHz today
with RC2) you will get good sounding results, but at bitrates that are not
competitive for state of the art voice. Passing your speech through a noise
gate prior to encoding is a must to keep the bitrate down in pure VBR modes.

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