ACELP | ADPCM | AMBE | AMR | AMR-NB | CELP | Codebook | DTMF | G.723 | G.726 | G.729 | GSM | Interpolation | LPC | LSF | LSP | MELP | PCM | Perceptual | Pitch | PSOL | QCELP | Quantization | SMV | VAD | Vocoder

im new to speech coding. Currently im trying to calculate speech 
recognition accuracy for TIMIT corpus which is coded using GSM and 
CELP 4.8kbps coder. im using HTK toolkit.

i find out the my speech recognition accuracy drop drastically when 
i tested coded speech using the acoustic model trained using NIST
(wav) file from TIMIT corpus.below i list down my method and can 
someone of you please clarify whether i done something wrong ? im 
doing phoneme recognition system.

1. i read Timit(nist) using matlab

2. resample it to 8khz 16 bit

3. then enter the resampled file as an input to codectest.c 
(HAWKCODER)

4. i get GSM and CELP 4.8 kb/s (lpc) as output in the format 
of '.au'.

5. then convert the GSM and CELP (au file) to MFCC_0_D_A (39) using 
Hcopy  

    from HTK (using config file)

6. later i insert the feature vectors to the trained acoustic model. 
i get results
WORD: %Corr=21.22, Acc=19.36 for GSM

but when i tested same TIMIT (Nist WAV) withoud coding 

WORD: %Corr=72.76, Acc=58.43

I just wan to know whether i had done the steps correctly or i had 
done something wrong? why my accuracy drop drastically? do you have 
any matlab code for GSM and CELP coder? or any info where i can it?

Waiting for your reply.Thank you for your help. 

Regards

Nash

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