re do we need the clipper for cheap security gtoal gtoal com graham toal writes can someone tell me if hardware compression is or is not needed to run digital speech down k i think it is i ve heard it s not lets say bit samples would raw data at the corresponding sampling rate be usable if not how fancy does the compression need to be note i am not a cable freak so i might have completely misunderstood what you said also my math is frequently noted for being wrong so you ll better check the calculations yourself i assume that k means k bits so if we assume one start and one stopbit and no protocol overhead the effective number of bytes per second is k let s also assume that you do not want to transmit your speech in stereo so that you can send samples sec this corresponds to a nyquist frequency of hz which should be too low especially if you think about the bit low quality sound furthermore your d a converter will probably not present you with a signal that has been cut off at hz but will instead alias in all the higher frequencies although you can definitely build a filter to overcome that problem on the other hand speech should be easily compressible for example you could form power spectra or you could simply band pass filter and then linearize the fourier transforms it won t be cd quality sound but it ll be discernible the power spectrum method is very good in that respect i have once programmed such a software compressor and compression rates of with relative errors due to linearization of less than were common although i must say that these were musical sounds not speech have fun stephan neuhaus informatik uni kl de sig closed for inventory please leave your pickaxe outside pgp public key available on request note the expiration date
