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Discussion Groups | Speech Coding | G729A CODEC application.
Technical discussions related to Speech Coding (all itu and other vocoders, ACELP, CELP, AMR, etc)
G729A CODEC application. - raghu kisore - Dec 21 11:58:00 2001
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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. __________________________________________________ |
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Re: G729A CODEC application. - Ganesan Ramachandran - Dec 21 15:33:00 2001
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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 |
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