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Título: bug in ayFx-ROM.asm from Shappire Publicado por: ARTRAG en 15 de Enero de 2009, 10:53:10 am I could be wrong, but investigating on the use of ayFX I think I have found a bug.
The ayFX player released here http://z80st-software.blogspot.com/ has a problem in the mixer: here we have: Código: @@SETMASKS: ; --- Set mixer masks --- ld a,c ; a:=Control byte and $90 ; Only bits 7 and 4 (noise and tone mask for psg reg 7) cp $90 ; If no noise and no tone... ret z ; ...return (don't copy ayFX values in to AYREGS) ; --- Copy ayFX values in to ARYREGS --- rrc a ; Rotate a to the right (1 TIME) rrc a ; Rotate a to the right (2 TIMES) (OR mask) ld d,$DB ; d:=Mask for psg mixer (AND mask) ; --- Calculate next ayFX channel --- ld hl,ayFX_CHANNEL ; Old ayFX playing channel dec [hl] ; New ayFX playing channel jp nz,@@SETCHAN ; If not zero jump to @@SETCHAN ld [hl],3 ; If zero -> set channel 3 @@SETCHAN: ld b,[hl] ; Channel counter @@CHK1: ; --- Check if playing channel was 1 --- djnz @@CHK2 ; Decrement and jump if channel was not 1 @@PLAY_C: ; --- Play ayFX stream on channel C --- call @@SETMIXER ; Set PSG mixer value (a:=ayFX volume) .... Cntering in this segment, C is the current control byte of the sfx. The segment analyzes bits 7 and 4 of C When we call SETMIXER, A is a mask derived from C, where only bits 5 and 2 have meaning. In SETMIXER we have this: Código: @@SETMIXER: ; --- Set PSG mixer value --- ld c,a ; c:=OR mask ld a,[AYREGS+7] ; a:=PSG mixer value and d ; AND mask or c ; OR mask ld [AYREGS+7],a ; PSG mixer value updated ld a,[ayFX_VOLUME] ; a:=ayFX volume value ret ; Return ayFX_END: ; --- End of an ayFX stream --- xor a ; a:=0 ld [ayFX_PLAYING],a ; There's no ayFX stream to be played! dec a ; a:=255 ld [ayFX_CURRENT],a ; Lower ayFX stream ret ; Return Thus, on exit, C has only bit 5 and 2 that can have meaning. The problem is now, as the following code pretend to read c as it were register 7 of the AY8910. The code in fact, tests for bit 2, 1 or 0 in branches for channels C,B and A Código: .... ld [AYREGS+10],a ; Volume copied in to AYREGS (channel C volume) bit 2,c ; If tone is off... ret nz ; ...return ld hl,[ayFX_TONE] ; ayFX tone value ld [AYREGS+4],hl ; copied in to AYREGS (channel C tone) ret ; Return @@CHK2: ; --- Check if playing channel was 2 --- rrc d ; Rotate right AND mask rrc a ; Rotate right OR mask djnz @@CHK3 ; Decrement and jump if channel was not 2 @@PLAY_B: ; --- Play ayFX stream on channel B --- call @@SETMIXER ; Set PSG mixer value (a:=ayFX volume) ld [AYREGS+9],a ; Volume copied in to AYREGS (channel B volume) bit 1,c ; If tone is off... ret nz ; ...return ld hl,[ayFX_TONE] ; ayFX tone value ld [AYREGS+2],hl ; copied in to AYREGS (channel B tone) ret ; Return @@CHK3: ; --- Check if playing channel was 3 --- rrc d ; Rotate right AND mask rrc a ; Rotate right OR mask @@PLAY_A: ; --- Play ayFX stream on channel A --- call @@SETMIXER ; Set PSG mixer value (a:=ayFX volume) ld [AYREGS+8],a ; Volume copied in to AYREGS (channel A volume) bit 0,c ; If tone is off... ret nz ; ...return ld hl,[ayFX_TONE] ; ayFX tone value ld [AYREGS+0],hl ; copied in to AYREGS (channel A tone) ret I think that in SETMIXER there is a missing bit that loads in C the value that the rest of the code tests. Shappire do you agree? IMHO a patch could be to add a ld c,a here Código: @@SETMIXER: ; --- Set PSG mixer value --- ld c,a ; c:=OR mask ld a,[AYREGS+7] ; a:=PSG mixer value and d ; AND mask or c ; OR mask ld [AYREGS+7],a ; PSG mixer value updated [b] LD C,A[/b] ld a,[ayFX_VOLUME] ; a:=ayFX volume value ret ; Return ayFX_END: ; --- End of an ayFX stream --- xor a ; a:=0 ld [ayFX_PLAYING],a ; There's no ayFX stream to be played! dec a ; a:=255 ld [ayFX_CURRENT],a ; Lower ayFX stream ret ; Return Título: Re: bug in ayFx-ROM.asm of Sapphire Publicado por: SapphiRe_MSX en 15 de Enero de 2009, 03:11:25 pm I guess it's not necessary, because the code is using
a -> OR mask (values for tone and noise bits of the channel, extracted from the ayFX control byte) d -> AND mask (a mask to preserve PSG mixer value except tone and noise bits) And as the initialization of these values is Código: ld a,c and $90 cp $90 (this instruction does not affect the value of a) ret z (neither this one) rrc a rrc a ld d,$DB (equivalent to %11011011) We know that in this moment the (maybe) active bits of the OR mask (in register a) are 0 on the AND mask (in register d). Lately, these values are rotated if the playing channel is not 1 (remember in the code 1 -> channel C, 2 -> channel B, 3 -> channel A) as follows: Código: rrc d rrc a So, when entering on @@SETMIXER subfunction we know that the only bits (maybe) active on register a (the bits of the control byte of the stream) are 0 on the register d (AND mask). Then, after executing @@SETMIXER Código: @@SETMIXER: ; --- Set PSG mixer value --- ld c,a ; c:=OR mask ld a,[AYREGS+7] ; a:=PSG mixer value and d ; AND mask or c ; OR mask ld [AYREGS+7],a ; PSG mixer value updated ld a,[ayFX_VOLUME] ; a:=ayFX volume value ret ; Return register c has the OR mask. And the value of the checking bit (2 for channel C, 1 for channel B and 0 for channel A) is the same on registers a and c, so the new instruction Código: ld c,a it's unnecessary. What do you think? Título: Re: bug in ayFx-ROM.asm from Shappire Publicado por: ARTRAG en 15 de Enero de 2009, 04:35:27 pm You are totally right! My patch is not needed
A is rotated 0 times for channel C, once for B and twice for A Thus for channel C we test bit 2 in C, for channel B we test bit 1, and for channel A we test bit 0! Sorry for the undue alarm! :P Título: Re: bug in ayFx-ROM.asm from Shappire Publicado por: ARTRAG en 15 de Enero de 2009, 09:35:00 pm In the end there was really the bug, but elsewhere.
Thanks Shappire!!! ;D PS The ayFX update is/wll be soon on Shappire's blog. Título: Re: bug in ayFx-ROM.asm from Shappire Publicado por: SapphiRe_MSX en 16 de Enero de 2009, 12:40:09 pm In the end there was really the bug, but elsewhere. Yes, a small one... I've not detected it because QBIQS do not use samples with noise. Citar Thanks Shappire!!! eeemm... Sapphire, Sapphire... not Shappire ;D ;D ;D Citar The ayFX update is/wll be soon on Shappire's blog Is there since yesterday night and maybe there will be a new update soon with some extra features that AR has included on the original code. Thanks again! -- Sph. Título: Re: bug in ayFx-ROM.asm from Shappire Publicado por: ARTRAG en 16 de Enero de 2009, 02:50:34 pm Sorry ! SapphiRe SapphiRe SapphiRe
(repeating myself to remember) SapphiRe SapphiRe SapphiRe SapphiRe SapphiRe SapphiRe SapphiRe SapphiRe SapphiRe SapphiRe SapphiRe SapphiRe ;D Título: Re: bug in ayFx-ROM.asm from Shappire Publicado por: ARTRAG en 21 de Enero de 2009, 02:22:47 pm SapphiRe has just released new replayers for AYFX!!!
Great work Fernando!!!! I love them! Título: Re: bug in ayFx-ROM.asm from Shappire Publicado por: SapphiRe_MSX en 22 de Enero de 2009, 03:33:45 pm ...and there is another update of the replayer, with a more compact code and a more correct treatment of frames with volume zero.
testing now... :P :P Título: Re: bug in ayFx-ROM.asm from Shappire Publicado por: Jon_Cortazar en 22 de Enero de 2009, 05:18:35 pm kool! ;) ;)
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