Lee O'D Posted January 10, 2013 Report Share Posted January 10, 2013 Hi, as usual I've got a bunch of questions...! I'm just trying to get my head around the current setup before I can then plan to contribute a bit more, sorry if it's annoying! So i've been trying to look at the HDL for the various sound generators and mixers. Slightly confused with the multiple sigmadeltas and the audiomixer... As far as I can tell, the audio mixer is working at 18 bit resolution (for the 3 inputs) with 20 bit accumulator for the output which of course is sigma delta'd into a 1 bit output. What's the clock rate of the final output currently? The SID seems to also be 18 bit output which is good... The YM (and POKEY) files seem to be 8 bit resolution output, but i couldn't see how this is mapped into 18 bits (or whether some implicit mapping to the more significant bits is taking place)? For the MOD output, the render resolution seems to be 16 bits mono (filled to both channels), again not sure how this turns into 18 bits? I'm also a bit confused by the zpuino_audiomixer.vhd vs the simple_sigmadelta.vhd files. If the audiomixer is providing the actual one bit conversion, is the simple_sigmadelta.vhd still used? Also as another question, can you comment on the MOD frequency (defined in a couple of places, eg in Retrocade.h as #define FREQ 17000 //Freq for modplayer) - is this a compromise between the speed of the zpuduino running the rendering code and not sounding too low-fi? Many thanks!! Lee Link to comment Share on other sites More sharing options...
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