Parse and convert a ym file to a simple set of registers to set per sample, either as a binary file or pure python.
Once built, do:
./convertym infile.ym outfile.psym
or
./convertym -p infile.ym outfile.py
for pure python output.
This is a slightly hacked up version of the StSound library that converts a YM file, e.g. from here, for the AY8913 chip into a format that pre-calculated and only includes the registers that actually change in in a sample, in a concise but non-compressed format.
This allows me to dump them onto an RP2040 and use micropython to just read the next set of registers to set and then send it to the Classic 8-bit era Programmable Sound Generator AY-3-8913 project on tiny tapeout 5: https://tinytapeout.com/runs/tt05/tt_um_rejunity_ay8913
Two file formats are available by default:
- the "psym" described below
- pure python (using the -p flag)
The file format produced is a header followed by N samples to be sent out to the chip at SAMPLERATEHz, where each sample is just the number of registers to set, then a pair of REGISTER,VALUE bytes for each one
header =========
PSYM1 (5 bytes)
CLOCKFREQ (4 bytes, little end)
SAMPLERATEHz (1 byte)
NUMSAMPS (8 bytes, little end)
/header =========
Followed by NUMSAMPS entry of form:
NUMREGSETTINGS (1 byte)
REGISTER (1 byte) and VALUE (1 byte) (NUMREGSETTINGS times)
Using the -p flag will output a file with a Song = [].
Each entry in the list is a sample. Each entry in the sample is a register setting, (REG, VAL)
SongInfo = {'clock': 2000000, 'rate': 2, 'num': 3646}
Song = [
[(0,0),(1,0),(2,0),(3,0),(4,0),(5,0),(6,0),(7,255),(8,0),(9,0),(10,0),(11,0),(12,0),(13,0),(14,0),(15,0)]
[(4,255),(7,251),(10,8),(13,15)]
[(0,214),(7,250),(8,9)],
# ...
]
To build, just compile and link all the files statically, e.g. for i in .cpp LZH/.cpp; do echo $i; g++ -ggdb -g3 -O3 -c $i; done; g++ -o convertym *.o
For a sample of how I actually use the file, see test_rejunity_ay8913