Sample player code for playing digis on the volume register of the Commodore 64 SID chip SID6581, in kickass assembly syntax.
Works only on the old C64, not the C64C, which has the newer SID8580 builtin.

This small demo code plays a loop from the old techno song "L.A. Style - James Brown is dead".

I use this occasionally to record "C64 distorted" samples, I love the crunchyness :)

Wav-samples must be prepared first: converted to 4bit/4kHz, and the raw sound data extracted (no file header). This is done in 2 steps: using sox to convert sample- and bit-rate. sox can not convert to 4bit well, so the 2nd step uses a quick'n'dirty c executable to do so from 8-bit encoding.
The output ("out.raw") is uncompressed and does not pack 2 4-bit digis into a byte.

The assembly code sources the binary file "out.raw".

The player is written in kickass assembly syntax - see kickass assembler: http://www.theweb.dk/KickAssembler/Main.html

use kickass to assemble:

java –jar /your/path/to/KickAss.jar digiplay.asm -o digiplay.prg

1) Use sox to convert to 8bit/4kHz:

sox -S jb.wav -r 4000 -b 8 -e unsigned-integer -t raw in.raw

2) Use 8to4bit to convert to 4bit/4kHz

The small utility 8to4bit.c can be used to create the final output file (creates out.raw):

cat in.raw | ./8to4bit 

get sox from source: http://sox.sourceforge.net/

git clone git://git.code.sf.net/p/sox/code sox
cd sox
autoreconfig -i
# configure script: remove warning definitions from 13540, 3 lines
./configure
make

or

apt-get install sox libsox-fmt-all