Simon Williams wrote:
Michael J. Mahon <mjmahon@aol.com> wrote: <SNIP>You've got me thinking about a version of DAC522 that _does_ use a zero duty cycle for $00 samples... And a preprocessor that ramps the average level up at the start and down at the end, to eliminate the pop problem. Hmmm...That would be cool... another feature that I'd like to see is interruptible playback. Having playback stop on a keypress might make DAC522 potentially more useful in games and other real-time interactive programs. (I've tried to do this mod myself, but I didn't have anysuccess)...
I've actually made a version that does that...send me email. ;-) And I've just tried a "ramping" sound preprocessor that subtracts the "negative envelope" of the sound from the samples, and "decays" back to 128 with a time constant of 40 milliseconds. The result is sounds that stay tangent to the $00 value, minimizing any "pop" at the beginning and end. It should be a fast transform in M/L. The downside is that it is a highpass filter that attenuates frequencies under 30Hz, but that is usually not a problem. It is also a nonlinear transform, so it is impossible to "undo" it to recover the original wave, but that is also not a big problem in most cases. -michael New Applesoft BASIC interface for NadaNet networking! Home page: http://members.aol.com/MJMahon/