Look ahead

Hi all,

The G.723 specification says that this codec has a 30 ms frame and 7.5 ms of
*look ahead*, thus resulting in the total *algorithmic delay* of 37.5 ms.

I have a few queries here:
1. Does *look ahead* mean that the G.723 encoder uses 1/4th of the *next*
(30 ms) frame for some decision making, while actually encoding only the
current frame ?

2. If yes, what kind of decision making is done on the basis of this
looked-ahead sub-frame ?

3. What is the significance of the term "algorithmic delay" here ?

4. Assuming that
	(a) the capturing routine fills one input buffer (corresponding to a 30 ms
frame) & gives it to the processor (encoder), which starts its processing,
and in parallel, the capturing routine continues filling the next input
buffer
	(b) the time taken to process (encode) one frame is negligible (~ 0 ms)

How/When does the encoder receive the 7.5 ms of data of the next frame ? Per
(b) above, I guess the data will not be ready to process ? Is the encoder
supposed to sleep/wait for some duration ?

Thanks,
Sharad

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