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G729A CODEC application.

Started by raghu kisore December 21, 2001
hi,

Description of the problem:
-----------------------
i have got the ITU standatrd G.729A CODEC application
written in c.along with the code i have got a test
file named TEST.INP
the TEST.INP has a 1.77 seconds raw speech data and
has 16 bit PCM value corresponding to the speech. For
every 10msec od speech 80 samples are obtained. This
is encoded by the encoder and a BITSTREAM file
TEST.BIT is generated which gives details regarding
pitch gain and codebook gains,pitch period and pulse
positions.for each 10msec frame.

the BITSTEAM file is used by the decoder to get the
output TEST.ONP block diagram for the process is
--------------------------------
encoding:

TEST.INP...encoder...BITSTREAM FILE decoding:
BITSTEAM FILE...decoder...TEST.ONP

My problem:
-----------
now i want to know if the 16 bit PCM values in the
TEST.ONP should be the same as those in TEST.INP(which
i think should be same, as iam not adding any noise to
the bitstream file).what i observe after running the
encoder and decoder is that there is diffrence in the
input values and the output values.(PCM values)

is the observed difference in the values dependent on
the efficincy of the speech coding?

thanks
Raghu. __________________________________________________



hi,
i'm not an expert in speech coding.. but as far as i
know, g.729 is a lossy compression algorithm.. as with
any lossy algo., the aim of decoding is not to
reconstruct the original waveform, but rather to
produce an acceptably close output that serves the
purpose..

for example, have you ever tried to convert CD to
mp3 and back to CD? you won't get the original quality
back..
hope this helps
regards,
ganesan

My problem:
-----------
now i want to know if the 16 bit PCM values in the
TEST.ONP should be the same as those in TEST.INP(which
i think should be same, as iam not adding any noise to
the bitstream file).what i observe after running the
encoder and decoder is that there is diffrence in the
input values and the output values.(PCM values)

is the observed difference in the values dependent on
the efficincy of the speech coding?

thanks