jjfeiler@nntp-server.caltech.edu (John Jay Feiler) (04/09/91)
I asked about conversion of mulaw codec sound to linear sound a few posts ago, and I guess I wasn't clear, because all I've gotten back is stuff I already know. Let me rephrase my question..... Does anybody have a neat, fast snippet of 56001 code that takes 8012 Hz mulaw encoded sound, and converts it to 22050 Hz 16-bit linear sound? I know about the mulaw table in the 56001 rom, but the trick is turning 4 samples into 11, ie, interpolation of the 8012Hz signal to a 22.05 KHz signal. I suppose I could just use linear interpolation, then filter out the noise above 8KHz, but I'm afraid that wont be fast enough (I'd like to be able to do this in as near to real time as possible). Possibly some kind of spline-like interpolation, where my delay would only be on the order of one (8KHz) cycle. It looks like NeXT does these conversions using the '040, but since I eventually want to do some fancier stuff with the signal in the DSP, and since I may also be combining signals from several sources, I'd like to keep everything in the 56001. Anyhow, thanks for any and all info, and thank you for your support... John Feiler