whats the differance between G.729 codec variations

Question

what is the difference between G.729 G.729A G.729AB

and if I have codecs set up for G729 in asterisk does this mean that G729A and G.729AB will work?

thanks

What have you read on it? What do the docs say, where have you found the docs? — Flummox - don't be evil SE, Dec 01 '16 at 08:44
docs say that G.729a is "Lower Complexity G.729" but it doesn’t mention compatibility — AvremyC, Dec 01 '16 at 09:40

score 2 · Answer 1 · answered Dec 04 '16 at 08:07

2

Asterisk support g729a only. So you have no other options.

G729b is not compatible with g729a, g729ab mean both variant supported by switch.

answered Dec 04 '16 at 08:07

arheops

score 1 · Accepted Answer · answered Dec 01 '16 at 16:00

G.729a is a compatible extension of G.729 that needs less CPU because it has lower speech quality. It is compatible with G729.

Some of its features are:

G.729b:

Not compatible with G.729 or G.729a
Has a silence compression method that enables the voice activity detection module (VAD). It is used to detect voice activity in the signal.
It includes a discontinuous transmission (DTX) module which decides on updating the background noise parameters for non speech (noisy frames).
Uses 2-byte Silence Insertion Descriptor (SID) frames transmitted to initiate comfort noise generation (CNG). If transmission is stopped, and the link goes quiet because of no speech, the receiving side might assume that the link has been cut. By inserting comfort noise, analog hiss is simulated digitally during silence to assure the receiver that the link is active and operational.

2 Answers2