[vorbis-dev] vorbis-utils features ;)

[Gregory Maxwell]

On Thu, Mar 22, 2001 at 01:47:45AM -0500, Keith Wright wrote:
> Is it true that a stream of constant exact zeros input will result in
> a very very low bit rate out?  (If not make it so.)

Yes.
 
> In that case it is "easy" to write a filter for the input that
> squelches at whatever level is appropriate to your application,
> and it seems obvious to me that that is the Right Way to do it.

This is called noise gating and it's really too simplistic to be that much
of a benifit.

Currently vorbis does a very smart, but consertive thing:
It doesn't know how loud you will be playing a file, so it can't assume it
can just throw out or quantize the hell out of quiet stuff. However, it does
know that the loudest sound within a sample ill not be louder then a certian
amount so we do have an upper bound on the volume level you will have it set
to. However, on quiet bits (like analog silence)  this is too consertive
(because there is no loud reference), I suspect that future encoder will be
smart enough to assume the listner won't be acting as a constant human
compressor and changeing the volume knobe between every block, thus it could
assume that the knob is set to no more then foo-dB louder then it was at
loudest point prior in the song. Then the rest of the algorithim can take
care of representing the unaudible bits with according quality.

This is a reletivly minor optimization which the format makes reletivly
easy for future implimentation and will require no decoder support. Right
now, it's more important to get all the features that require decoder
support implimented right.

Right now it is useful to think of vorbis as currently developing a decoder
rather then an encoder.. Yes, there is an encoder.. There has to be one to
develop the format, however features that are not essential to the
development of the decoder or adoption of the format are not high priorities.

Look at the early mp3 encoders (like the orignal FhG encoder) and compair
their quality to the modern stuff (like lame). Considering where vorbis is
today (better then the best mp3 encoders almost entirely across the board),
it really excites me about the quality we can expect tommorrow (from the
same decoders even!).

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