Blitter sound routine

[charles]

can you help me with how the timer and setting he tempo is accomplished?

[metalages]

The score is interpreted at each frame (50hz).
The $F (15 in decimal) effect allow to specify how many frames a line into the score will last.
For lowest tempos there is another calculation method as described in the mod format
http://www.textfiles.com/programming/FO ... d-form.txt
(look at 15 Set speed effect)

[charles]

thanks ....ive been trying for years to implement a tempo adjust for a midi playback routine I wrote by adjusting the timers resolution...maybe this will help .....
brace yourself
ill prob have more questions

[vinz6751]

I don't have anything to contribute but I really like this discussion, great job

[metalages]

Thanks

[metalages]

Major update of the sound routine available here :

https://github.com/gibs75/demOS
https://github.com/gibs75/demOS/tree/ma ... CS/BLITSnd
https://github.com/gibs75/MilkyTracker-fork

(this version used in this prod https://www.twitch.tv/videos/1553977161?t=8h17m22s)

- 4 + 3 voices with added support for standard YM (no timer) voices
- conversion from .xm files allows variable length patterns
- more tools

[RA_pdx]

Really great work, metalages!

[metalages]

Thank you
Also the result of the great tunes by Dok

[viking272]

This is really cool, great work! I played the Twitch stream and cranked up the volume.
Soon I had all the kids in the study jumping and dancing away! Great memories

[metalages]

[metalages]

I think about adding a new feature.

Currently we have an hybrid configuration with voices blittered PCM / YM with their own pro / cons :
- YM :
* portamento (variable freq)
* squares (except if the STe has LCM -12db mix hardware fix) because of mixing level. only 10/11 volume levels (else it is too loud)
* no YM interrupt effects (the goal is to fit the upper border, also interupts would collide with blitter when running) => no pulse width
- blittered PCM :
* no portamento (pre determined frequencies)
* steep volume effects (7 levels / -6 db steps)
* samples (looping or not)
* dynamic bit decimation

The new feature would provide something in between what YM and current PCM routine offers.

This new feature will be a blittered PCM square.
The square wave is specifically convenient because of its constant values, so you can loop the blitter where you want Because of this, with only one source square sample in memory and setting up the loop accordingly it would give :
* portamento (variable freq)
* square on 127 volumes step (with input value of 0 or 127 constant, volume can be done throught half tone masking)
* variable pulse width

[shoggoth]

PWM sounds nice (pun intended)

[metalages]

PWM sounds nice (pun intended)

Pun ackowledged

[metalages]

Quick & dirty test
https://youtu.be/tvO1BLg9iSk

[shoggoth]

Sweet!