[Speex-dev] Historical question

Björn Thalheim s9268716 at mail.inf.tu-dresden.de
Thu Aug 10 01:24:42 PDT 2006

Hello Jean-Marc and all,

I recently had a talk with somebody about CELP. He said, there is this
federal standard 1016 (4.8kbps) with a reference implementation of the
Department of Defense (only on Sun, unfortunately, if I got this right).
This one is noticed in the manual already.

He also said, since there is this implementation of the DoD, nobody
would voluntarily re-implement CELP.

If I read the manual, I guess you just took the idea names CELP, did
some conceptual work (resulting in NB, WB und UWB mode as well as all
these bitrates Speex supports, as well as stuff like frame-length and
number of subframes) and then actually made a new implementation (DoD
CELP is far less than Speex).

So the Question is: did you take any code from DoD CELP?
What would happen, if I took a 8kHz-Wav file and did
	speexenc -n -.bitrate 4800 file.wav file.spx
Would the result of this be comparable to a DoD-CELP encoded file?
Besides all the other bitrates and sampling-rates, how does speex differ
from DoD CELP (I unterstand Speex is using frames of 20ms with 4
subframes, DoD CELP uses 30ms frames with 4 subframes, but this is about
it what I know)?
Does Speex extend DoD CELP or does it only pick up the same idea (CELP)
and has nothing more to do with DoD CELP?



Blow it out your ear.

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