Hi,
The primary difference is the processing power needed for each individual codec g.729 Vs 729a as an example not much difference from a quality standpoint.
The difference being the number of medium VS high complexity VoCoders
calls
processed example
g.729a medium 17 MIPS Vs 34 MIPS g729 high complexity.
Smaller codebook used for g.729a
The G.729 speech codec uses the conjugate-structure algebraic code excited
linear-prediction(CS-ACELP) algorithm, which is an analysis-by-synthesis
algorithm and belongs to the class of speech coding algorithms known as code
excited linear prediction (CELP). Therefore, the speech decoder is primarily
a subset of the speech encoder. For every 10-ms speech frame, thespeech
signal is analyzed to extract the parameters of the CELP model
(linear-prediction filter coefficients, adaptive and fixed-codebook indices
and gains). The G.729A is the annex A forG.729 to reduce complexity of the
CS-ACELP speech codec .
Analog voice is received by a CODEC (coder / de-coder)
* Complex circuitry then samples the voice and compares the voice to a
codebook. This codebook is used by both the coders and decoders.
* Once sampled and matched with the codebook the voice is now
presented as data
* Some codebooks are of different sizes and have a different fidelity
* These codebooks are "recommended standards" that copies voice
samples into different sizes
* Codec standards:
G.711 changes voice into data but uses the same amount of space as an
analog
method. Uses 64Kcodebook. This codebook is used by both the coders and
decoders.
* Once sampled and matched with the codebook the voice is now
presented as data
* Some codebooks are of different sizes and have a different fidelity
* These codebooks are "recommended standards" that copies voice
samples into different sizes
* Once sampled and matched with the codebook the voice is now
presented as data
* Some codebooks are of different sizes and have a different fidelity
* These codebooks are "recommended standards" that copies voice
samples into different sizes
* Codec standards:
G.711 changes voice into data but uses the same amount of space as an
analog
method. Uses 64K
G.729 Uses a large codebook but sounds good at 1/8 of G.711. Uses about 8K
G.729A Codebook smaller than G.729
* Complex circuitry then samples the voice and compares the voice to a
codebook. This codebook is used by both the coders and decoders.
* Once sampled and matched with the codebook the voice is now
presented as data
* Some codebooks are of different sizes and have a different fidelity
* These codebooks are "recommended standards" that copies voice
samples into different sizes
* Codec standards:
G.711 changes voice into data but uses the same amount of space as an
analog
method. Uses 64K
G.729 Uses a large codebook but sounds good at 1/8 of G.711. Uses about 8K
G.729A Codebook smaller than G.729
http://www.cisco.com/en/US/tech/tk652/tk701/technologies_tech_note09186a00800b6710.shtml
regards
Allan
