Dear Musafi, I was checking the references I have on the MELP, and I found two articles, which I have forgotten about, that maybe useful for your work: [1] Alan McCree and Juan Carlos De Martin, "A 1.7 KB/S MELP CODER WITH IMPROVED ANALYSIS AND QUANTIZATION", ICASSP'98. [2] Alan McCree and Juan Carlos De Martin, "A 1.6 KB/S MELP CODER FOR WIRELESS COMMUNICATIONS", IEEE SPEECH CODING WORKSHOP, PENNSYLVANIA, SEPTEMBER 1997, pp.23-24. I check them quickly, and contrary to what I advised you in my last posting, they reduce the frame length from 22.5 ms to 20 ms. They also improved pitch and voicing estimation and added a noise supression front-end. The bit rate decrease comes from: - better LSP quantization, instead of 25 bits, 21 bits in [1] and 20 bits in [2]. - removed the Fourier magnitudes (8 bit saving). - transmit the gain only once per frame, as the frame is now shorter (from 8 to 5 bits). - reduce from 7 to 6 the bit used for pitch and overall voicing - changed (removed, saving of 1 bit) the aperiodic flag by a "pitch contour perturbation technique" (please do not ask me what it is :-) - reduced the number of bits for bandpass voicing from 4 to 2, by selecting from a catalog of of 4 partial voicing patterns. - the sync bit was removed. I have the impression that they really squezed every possible bit, and still they are at 1.6 kbps. Maybe for further reduction you would lose some quality. Do not forget to check the 4 kbps in the ICASSP'99. Regards, Sara |