Amiga sound playback routine/format questions

[amigaksi]

> Yeah, I do get 3.3:1 compression in my Gita multimedia CD
This is probably due so relatively silent parts in the samples and/or the 8bit quantisation.
Try the same on some randrom music in 16bit. In average, you wont get better than 1:2 when you go loosless.
http://wiki.hydrogenaudio.org/index.php?title=Lossless_comparison

And Amiga_Nut needs something fast enough for a nacked A500 that should do some GFX in the meanwhile.

Thanks for that link-- I didn't realize my link was also in that article: http://www.krishnasoft.com/sps.htm.  I never promoted my audio software but I guess someone did it for me.  I did say 8-bit in my post #5 and it does work on stock Amiga at 7.16Mhz as the decompressor is very fast (faster than playback rate).  All speech and even some music have silent parts; it's part of natural sentence structure.  But even the silence is noisy in my audio as it was digitized from cassettes and there's that "hiss" type of noise when someone pauses between words.

[amigaksi]

If Paula is a 14bit DA Converter, what is the "calibration" for then?

As for th downsampling, this is another story, but can be done "offline". I used to do 44.1kHz with interrupt, but on a 68060.
With dithering I mean to reduce (or better mask, it is some kind of noise shaping) the audible quantisation noise. Just like dithering in images with low bit depth.

I think the logic is that if it's not a linear 14-bit DAC then a table helps to map 16-bit data to the nonlinear 14-bits optimally rather than approximate with LSR.W #2,D0.

[Thorham]

If Paula is a 14bit DA Converter, what is the "calibration" for then?

Paula is 14 bit because both sample and volume data are handled by Paula.

The calibration part is only needed to compensate for the non-linearities in the audio hardware, probably the analog parts, but I'm not sure. Seems reasonable (all Paulas are the same?).