Pitch calculation error

digital-sound-antiques / vgm-conv

Chip-type and clock converter for VGM

ISC License

45 stars 3 forks source link

Pitch calculation error #42

Closed denjhang closed 3 years ago

denjhang commented 3 years ago

截图未命名0817193238 截图未命名0817193308 The lowest note of NGP should be G2 or lower, but after conversion to AY8910, the lowest note is only A2

okaxaki commented 3 years ago

I have two questions.

Does this issue only occur on NGP conversion? Is it okay for other SN76489 vgms?
Is the sound of the AY8910 detuned, or is it that the audible pitch is correct but the MDPlayer shows an incorrect pitch?

okaxaki commented 3 years ago

If your vgm's NGP clock is 307200Hz, please make sure pitch on the MDPlayer keyboard is correct. If MDPlayer assumes 3579545Hz clock, MDPlayer shows 2 lower semi-tones for a 307200Hz vgm.

denjhang commented 3 years ago

I can make sure that the pitch displayed by MDPlayer is correct. Because I have reported a problem in the pitch calculation of SN76489 with a frequency other than 3,575,545 hz a long time ago https://github.com/kuma4649/MDPlayer/issues/124. This problem was fixed soon, which means that currently MDPlayer considers the difference of the clock when calculating the pitch.

denjhang commented 3 years ago

Currently AY8910 sound is detuned. In NGP, all sounds lower than A2 become A2 of AY8910.

denjhang commented 3 years ago

ngp-sonic.zip

denjhang commented 3 years ago

I found that not only the NGP, but also the pitch conversion error for the SN76489 that does not use the 3579545hz clock.

denjhang commented 3 years ago

lickspat.zip

okaxaki commented 3 years ago

Okay I got the point. Current vgm-conv internally convert SN76489's clock to 3579545Hz. At this clock, the note's lower limit is A2. I'll fix this problem but it will take some time.

Workaround: it is possible to get a correct conversion result with -c option that specifes the destination clock as the following.

vgm-conv -f sn76489 -t ay8910 -c 1536000 -o 1536000.vgm input.vgm
vgm-conv -c 1789773 -o output.vgm 1536000.vgm

okaxaki commented 3 years ago

Fixed at 0.8.21