Hi all, Just read the description of the GSM codec, and I think it should be modified slightly: Original: GSM 06.10 is a standardized lossy speech compression employed by most European wireless telephones. It uses RPE/LTP (residual pulse excitation/long term prediction) coding to compress frames of 160 13-bit samples with a frame rate of 50 Hz into 260 bits. Proposal: GSM 06.10 is a standardized lossy speech compression employed by first generation of digital mobile phones in Europe. It uses RPE/LTP (residual pulse excitation/long term prediction) coding to compress frames of 20 ms, achieving a bitrate of 13kbps. Why these changes? 1. Modern GSM phones use GSM 06.20 (Half Rate codec, CELP, 5.6 kbps) or GSM 06.60 (Enhanced Full Rate, CELP, 12.2 kbps), at least the latter has a better quality, so the original statement can be misleading for people used to typical quality of gsm. 2. Frames of 160 samples and framerate 50 Hz is redundant, and giving the framelenght (20 ms) instead of framerate is consistent with the other descriptions and easier to understand (IMHO), as it is also the coding delay. Sample resolution of 13 bits is irrelevant, as it is only a technical detail and gives no information about quality, it is not the limiting factor. Greetings, Stefan -- Stefan Brüns / Kastanienweg 6 - Zimmer 1206 / 52074 Aachen mailto:lurch gmx li http://www.kawo1.rwth-aachen.de/~lurchi/ phone: +49 241 169-4206 mobile: +49 160 7532733
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