CVSD is a scheme that uses 1-bit samples at a relatively high sample rate. Rather good quality voice can be had at 32 kbits/sec. 16 kbits/sec is quite usable. CVSD stands for "Continuously Variable Slope Delta" modulation. It works by having the transmitter and receiver both maintain a model of the signal. If the instantaneous value of the signal is higher than the transmitters understanding of what the receiver will think it is (based on tracking the model), the transmitter will send a zero, otherwise it will send a one. Whats makes it 'Variable' is that the step size is increased whenever the the transmitter finds itself sending a sequence of more than a couple of consecutive zeros (or ones), which indicates the transmitted bit stream isn't 'keeping up' with the changes in the signal. When the signal isn't repeated zeros (or ones) then then step size is reduced to hopefully allow the ouput to track small signals more acccurately. Bob Ammerman RAm Systems ----- Original Message ----- From: "Jinx" To: Sent: Tuesday, December 11, 2001 5:20 PM Subject: Re: [PIC]: CSVD or other on PIC (compress audio) > After wondering about the compression procedure of the audio > DSP, I got to thinking "Eh ?". If each block of 8 bits of data is > expanded to 10 bits by left shifting and 0 padding, then are the > functions of the Estimate and Syllabic Integrators to sense trends > in the waveform and replace the LSB "00" bits with fill-in values ? > It's the only way I can see to get 10-bit quality sound from 8 bits > of data. 8 bit audio does not sound very nice at 16kHz (which is > originally sampled at 64kHz), and the DSP's output is definitely OK > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body