PT3 shorter replayer

I have just emulators as well.

BTW have you ever seen a ZXspec demo named apology that is a demonstration of producing 6-channel sound from the 3-channel AY?
The idea that appears from the code (that is open) is genial apart from a bug in the use of AY levels that implies some non linear artifacts.

As far as i can see the player is CPU intensive, but much lighter that a PCM player, as the sole task that
the z80 have, is counting the period duration of the 6 squared waves.
Actually, while counting, you can do also other things.

have a look
http://www.west.co.tt/matt/speccy/apology/

PS
the error in the AY levels can be easily corrected...

PPS
PT3 files ues 3 channels, but with 6 channels one could do many things

If you know the demo I need to point you that
the aplogy player has a problem with the AY levels that
are NOT linear.

Look at this example:

let x be the value corresponding to the first channal of the AY (let's say CHA),
bchan,cchan are the logical channels mapped on this sole phisical channel

for bchan = off & cchan = off, Apology uses x=0
for bchan = on & cchan = off, Apology uses x=8
for bchan = off & cchan = on, Apology uses x=7
for bchan = on & cchan = on, Apology uses x=15

But this means a very distorted square wave as the resulting levels are

for bchan = off & cchan = off, use x=0 => CHA = 0
for bchan = on & cchan = off, use x=8 => CHA = 0,0884
for bchan = off & cchan = on, use x=7 => CHA = 0,0626
for bchan = on & cchan = on, use x=15 => CHA = 1

this is due to the fact that the volume levels go like 2^(x/2)/2^(7,5)

the corrrect strategy should be

for bchan = off & cchan = off, use x=0 => CHA = 0
for bchan = on & cchan = off, use x=13 => CHA = 0,5
for bchan = off & cchan = on, use x=15 => CHA = 0,5
for bchan = on & cchan = on, use x=15 => CHA = 1

I was thinking to a port of the (corrected) algorithm to msx...

I've just tested the code and seems to work fine in MSX1, MSX2 and TR. The only minor flaw is a short fuzzy noise at the beginning of the song, it doesn't sound at the begginning of the loop anyway...

6 Channels from PSG?That´s a COOL thing

Final version !!!

This is the msx version of Matt Westcott's PSG 6 channel player for Spectrum.
As far as I can understand, this version corrects a problem of the original source
due to the non linear behaviour of the DAC in the PSG.
Thanks to Matt Westcott (aka Gasman) for its idea and code (and music)!!

        OUTPUT  apo.com
        org #100
          
        ld a,7          ; turn off AY's wave generator.
        out (#A0),a
        ld a,63
        out (#a1),a

        ld  ix,vols

        ld  bc,#11      ; init all counters
        ld  de,bc
        ld  hl,bc

main    di

mainloop
               
        exx             ; update note period only at 50Hz
datpos  ld hl,dat       ; store here note lenght

        ldi a,(hl)
        ld (bchan+1),a

        ldi a,(hl)
        ld (cchan+1),a

        ldi a,(hl)
        ld (dchan+1),a

        ldi a,(hl)
        ld (echan+1),a

        ldi a,(hl)
        ld (hchan+1),a

        ldi a,(hl)
        ld (lchan+1),a

        ldi a,(hl)
        or a
        jp z,fin
        ld (datpos+1),hl

        exx
 
        ld  iyh,a
        ld  iyl,0        
loop
        dec b           ; the wonderful main loop.
        call  z,bchan     ; registers b, c, d, e, h, l
        dec c           ; contain period counters for each channel.
        call  z,cchan     ; When they reach zero,
        dec d           ; do something important.
        call  z,dchan
        dec e
        call  z,echan
        dec h
        call  z,hchan
        dec l
        call  z,lchan

        dec iyl
        jp  nz,loop                 
        dec iyh
        jp  nz,loop         

        jp  mainloop
fin        
        ei

        ret

;------------------
bchan   ld b,0      ; note period will be poked here -
        ld a,8      ; select AY channel A volume register
        out (#A0),a
        ld a,01b    ; we will flip b0 to generate tone
        jp 1F

cchan   ld c,0      ; note period will be poked here -
        ld a,8      ; use AY channel A here, too
        out (#A0),a
        ld a,10b    ; we will flip b1 this time
1
.rechan xor 0           ; flip the appropriate bits of the
        ld (.rechan+1),a   ; stored levels
        ld (.tabvol+2),a   
.tabvol ld  a,(ix+0)
        out (#A1),a   ; and write back to the AY
        ret
;------------------
dchan   ld d,0  ; do exactly the same thing
        ld a,9  ; for all other channels
        out (#A0),a
        ld a,01b
        jp 1F
        
echan   ld e,0
        ld a,9
        out (#A0),a
        ld a,10b
1
.rechan xor 0           ; flip the appropriate bits of the
        ld (.rechan+1),a   ; stored levels 
        ld (.tabvol+2),a   
.tabvol ld  a,(ix+0)
        out (#A1),a
        ret
;------------------
hchan   ld h,0
        ld a,10
        out (#A0),a
        ld a,01b
        jp 1F
        
lchan   ld l,0
        ld a,10
        out (#A0),a
        ld a,10b
1
.rechan xor 0           ; flip the appropriate bits of the
        ld (.rechan+1),a   ; stored levels 
        ld (.tabvol+2),a   
.tabvol ld  a,(ix+0)
        out (#A1),a
        ret
;------------------


vols    db  0,13,13,15


dat   
        db 1Fh,27h,34h,4Fh,67h,1Fh,38h,29h,37h,42h,52h,6Eh,A8h,38h,1Eh,28h
        db 3Ch,5Fh,76h,BAh,50h,24h,28h,3Dh,48h,61h,BBh,60h,1Ah,27h,34h,4Eh
        db 4Fh,7Ch,78h,24h,28h,35h,47h,6Bh,6Bh,40h,24h,2Ah,3Bh,47h,6Bh,D5h
        db 38h,1Eh,2Ah,3Bh,47h,6Bh,D5h,48h,20h,28h,3Fh,50h,6Ah,9Fh,30h,1Ah
        db 35h,3Fh,4Fh,6Ah,9Fh,38h,13h,1Eh,25h,3Ch,5Bh,B6h,70h,23h,27h,47h
        db 38h,5Fh,B6h,40h,14h,22h,28h,44h,65h,C9h,60h,27h,2Ah,4Fh,5Eh,7Fh
        db BCh,50h,49h,56h,56h,6Dh,7Dh,D8h,30h,3Dh,49h,56h,6Dh,6Dh,D8h,30h
        db 40h,51h,51h,6Dh,A3h,D8h,30h,35h,40h,4Fh,6Ah,6Ah,9Ch,38h,1Fh,33h
        db 3Dh,67h,3Dh,9Eh,60h,3Bh,3Fh,5Eh,6Ah,6Ah,9Ch,50h,22h,39h,51h,6Ah
        db A4h,A4h,60h,3Eh,46h,6Ah,6Ah,A6h,A6h,60h,3Bh,4Fh,5Eh,78h,BDh,BBh
        db 2Ch,2Fh,4Fh,5Eh,78h,BDh,BBh,2Ch,29h,3Bh,52h,67h,8Bh,CDh,2Ch,22h
        db 3Ah,52h,67h,8Ah,CDh,34h,16h,21h,2Ch,6Fh,DEh,DDh,58h,28h,2Dh,51h
        db 76h,74h,E7h,50h,19h,25h,32h,4Bh,97h,EAh,50h,2Eh,34h,4Eh,5Ch,82h
        db FFh,50h,28h,3Ah,52h,89h,CFh,CFh,2Ch,22h,3Ah,52h,89h,CFh,CFh,2Ch
        db 1Ch,2Ch,38h,4Bh,5Ah,9Dh,2Ch,2Dh,4Dh,39h,4Ch,5Bh,9Dh,30h,34h,3Ah
        db 45h,68h,A6h,A6h,50h,28h,3Ah,52h,89h,CFh,CFh,28h,22h,3Ah,52h,89h
        db CFh,CFh,28h,1Ch,2Ch,38h,4Bh,5Ah,9Dh,28h,2Dh,4Dh,39h,4Ch,5Bh,9Dh
        db 30h,34h,3Ah,45h,68h,A6h,A6h,50h,28h,3Ah,52h,89h,CFh,CFh,30h,22h
        db 3Ah,52h,89h,44h,CFh,30h,1Ch,2Eh,38h,4Bh,60h,9Eh,24h,26h,4Bh,61h
        db 74h,61h,F3h,24h,30h,61h,EAh,74h,61h,F3h,28h,34h,44h,67h,8Fh,A4h
        db A4h,40h,34h,4Eh,67h,9Ah,BAh,BAh,40h,34h,52h,6Ah,6Bh,D6h,D7h,30h
        db 3Bh,4Fh,5Eh,6Bh,D6h,D7h,30h,46h,53h,69h,76h,D6h,D7h,60h,1Dh,24h
        db 31h,49h,61h,8Fh,40h,25h,32h,3Ah,4Ah,64h,93h,40h,1Bh,24h,36h,56h
        db 6Ah,ABh,40h,21h,25h,38h,42h,58h,ABh,48h,18h,24h,30h,74h,92h,FBh
        db 70h,21h,25h,31h,42h,63h,C5h,30h,21h,27h,31h,42h,63h,C5h,30h,1Ch
        db 27h,31h,42h,63h,C5h,48h,1Dh,25h,31h,49h,63h,92h,A0h,00h