At 4:22 PM -0800 4/1/99, Craig Latta wrote:
>	Hmm. I think MP3 at 128kbps or higher sounds very much better than RealAudio. The "no loss of quality" claim isn't completely silly (only mostly)... If the source has already been severely compressed spectrally (or just doesn't have any very low or high frequencies) then it compresses very well. :)

Has anyone listened to the Voxware music (MetaSound) codecs? To my
ears, the quality of their 96kps stereo codec is better than the
128kps MP3, and the sound is very decent even at 48kbps (although
that bitrate drops the sampling rate to 22050 with the corresponding
loss of those sparkling high frequencies).

But the truely stunning codec I've heard is the QSound one. If
you have Quicktime 3.0 or better installed, you can listen to
samples of this at www.qsound.com. They can stream CD-quality
sound over a 28.8 modem! How do they do it? Apparently by expending
a LOT of work in analysis during encoding. On a P133, it takes
over an hour to encode 10 minutes of music. But decoding is
real-time.

Quicktime includes decoders for Voxware, QSound, and MP3, and
QT is available for both Win32 and Mac. Thus, it might make sense
to add a Squeak primitive that can access the Quicktime
codec library.

Incidentally, Squeak 2.4 includes a SoundCodec hierarchy that
currently includes ADPCM (2, 3, 4, and 5 bit), GSM 6.10, mu-Law,
and an experimental Wavelet-based codec. But none of these
codecs approaches the compression ratios and quality levels
of the commercial codecs mentioned above.

Pointers/Compression Expertise Wanted

The Squeak team would be *extremely* interested in pointers to
publicly available source code, standards docs, or algorithm
descriptions for high quality codecs that we could incorporate
into Squeak. Something like the GSM source code from Jutta Degener
and Carsten Bormann of the Technische Universitaet Berlin
(which we're using for the GSM codec) would be perfect. Or,
if any of you Squeakers is an expert on sound compression
and might be interested in implementing a codec in Squeak
(for translation to C), please let us know. Thanks!

	-- John

P.S. The GSM codec is rather large, so it is packaged as a
Squeak plugin. Plugins have been compiled for Win32 and MacPPC
and the C source code for GSM will be included in the 2.4 release.
P.P.S. We already know about the two ADPCM implementations on
ftp.cwi.nl/pub/audio/.