Blitter sound routine

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charles
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Re: Blitter sound routine

Post by charles »

can you help me with how the timer and setting he tempo is accomplished?
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metalages
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Re: Blitter sound routine

Post by 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)
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charles
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Re: Blitter sound routine

Post by 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 .....
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Re: Blitter sound routine

Post by vinz6751 »

I don't have anything to contribute but I really like this discussion, great job :)
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metalages
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Re: Blitter sound routine

Post by metalages »

Thanks :)
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Re: Blitter sound routine

Post by 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
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Re: Blitter sound routine

Post by RA_pdx »

Really great work, metalages!
>> > raZen/Paradox < <<

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Re: Blitter sound routine

Post by metalages »

Thank you :)
Also the result of the great tunes by Dok ;)
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Re: Blitter sound routine

Post by 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 :)
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Re: Blitter sound routine

Post by metalages »

:)
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Re: Blitter sound routine

Post by 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 :)
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Re: Blitter sound routine

Post by shoggoth »

PWM sounds nice :) (pun intended)
Ain't no space like PeP-space.
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metalages
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Re: Blitter sound routine

Post by metalages »

shoggoth wrote: Wed Dec 21, 2022 11:05 am PWM sounds nice :) (pun intended)
Pun ackowledged ;)
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metalages
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Re: Blitter sound routine

Post by metalages »

Quick & dirty test
https://youtu.be/tvO1BLg9iSk
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Re: Blitter sound routine

Post by shoggoth »

Sweet!
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