Question 22/XV - Encoding for stored digitized voice signals
(Continuation of Question 29/XVIII 1985-88)

Considering

(1) that for the purpose of providing voice or multi-media store and
forward messaging a method of representing voice as a bit string for
storage and transmission purposes is required;

(2) that the encoding scheme should provide a low bit rate output in
order to decrease the cost of message storage and, to a lesser extent,
of transmission;

(3) that the decoding scheme should operate in real time and that the
costs should not be too high;

(4) that the voice quality should not be significantly different from
current 64 kbit/s PCM transmission,

What encoding scheme should be recommended for voice in the context of
store and forward messaging?

Points for study

1.The possibility of the scheme providing, or being able to evolve to, a
very low bit rate algorithm, perhaps by silent period suppression.

2.The possibility of keeping costs down by the specification of an
algorithm which can be implemented on a single IC.

Notes

1. Multiple conversions, e.g. analogue-to-digital and back-to-digital,
will not be required.

2.Voice band data will not have to be carried.

3. Algorithms developed under Questions 21/XV and 23/XV could also be
used for the encoding of stored voice, especially when associated with
suitable methods for silent periods suppression.

4. Account should be taken of the work of Study Group XVIII on the ISDN
and general network issues.

5. Account should be taken of the work of Study Group XII on subjective
testing issues.