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Assembly Source File | 1992-07-10 | 14.5 KB | 357 lines

; QBTWEAKR.ASM By Rich Geldreich 1992 ; For QuickBASIC 4.5 or PDS 7.1 ; ; Plays simple, 8-bit digitized sounds over the PC-Speaker. No ; bells. No whistles. Have fun. This code is in the public ; domain. It's yours now! All I ask is that you give credit where ; credit is due. Assembled with TASM v2.00 - should also assemble ; with MASM 4.00 too(that's all I had to test it out with, sorry)... ; ; Notes: My play interrupt does not call the original interrupt 08h ; routine every 18.206 times a second, therefore, the BIOS clock ; will stop dead while you're playing sounds. It doesn't matter ; what you set the main interrupt rate to; samples will always play ; at the same frequency. The main difference is quality; an ; interrupt rate of 18,000hz sounds much, much better than ; 10,000hz, of course. Many functions could be added to this ; program, such as volume, echo, 2 or more channels, etc. The ; program as-is only plays signed samples, if you play a sample ; which seems distorted, try unsigning it(or reassembling this ; program, see the interrupt procedure). That's all for now. If ; you find any bugs, tell me about them and I'll do my best to fix ; 'em. ; ; I've also included the small QB program that made the pc-speaker ; translation table. (This program can be easily modified for ; other devices, such as an 8-bit DAC on a printer port, or even ; the Adlib.) ; ;Functions provided: ; ;TweakOn freq% ; Captures interrupt 08h, the 18.206hz timer click interrupt. ; Reprograms the 8253 timer chip to whatever frequency passed by ; freq% (in hertz). You'll should hear a little click from your ; speaker when you call this function. (Valid range for freq% is ; 1-40000.) ; ;TweakOff ; ; Frees interrupt 08h, and reprograms the timer back to what it used ; to be. You must do this before your program ends! (Actually, you ; don't because QB and PDS restore the vector to interrupt 08h. It's ; best to be safe, though. You should always call this function before ; you start editing your program in the environment, just in case...) ; ;PlaySound Offset%, Segment%, Length%, Frequency% ; Plays a sample at a "virtual" frequency over the pc-speaker. ; Offset%, Segment%, & Length% specify the location of a sample in ; memory. Frequency% specifies the frequency(in hertz) that the ; sample will be played at. (Note: if you set interrupt 08h to ; 10,000hz, and you play a sample at 20,000hz, exactly 1/2 of the ; samples will be skipped, so it will sound like 20khz. All of the ; frequencies above the interrupt rate will be adjusted similar to ; this...) ; ; TweakStatus () Function ; Returns -1 if sample is playing. Returns 0 if a sample is not. ; ; Stuff you can't do while using this driver: ; ; I've tested this program in the environment, and it seems to work ; fine, although I still don't recommend that you let the interrupt ; go while editing your program!! For instance, if you edit your ; program and make it smaller, while my interrupt is going, QB may ; try to move memory around and my play interrupt may crash and ; burn. One thing though: QB and PDS disable interrupts while ; you're in the editor. This causes distortion in the sound because ; my interrupt doesn't get all of the time it deserves. You can't ; use the SOUND, PLAY, or SLEEP commands, because they use interrupt ; 08h for timing. You can't SHELL to dos, because QB restores ; interrupt 08h before going under. In other words: Don't use any ; commands that leach off interrupt 08h! I don't recommend that you ; access any mass-storage devices while playing samples, doing so ; may cause distortion. ; ; All of these routines were derived from my QB .MOD player, which I ; will (hopefully) be releasing soon. ; ; (Another last minute note: Be carefull using this program in the ; environment, if you press ctrl+break and the interrupt is still ; going, go to the immediate window and type "TweakOff". Also note ; that the interrupt routine can still be going even though it isn't ; producing any sound! Use caution!) ; ; And finally, here's what I need: ; If anybody has got an assembly routine that emulates QB's "PLAY" ; command, please let me know if you're willing to share it. I'm ; making an ANSI emulator in assembly, and it would be great if it ; supported ANSI music. I'd make it myself, but I just don't have ; the time these days... Thanks! public TweakOn, TweakOff, PlaySound, TweakStatus cseg segment para public 'CODE' assume cs:cseg, es:nothing, ds:nothing ;Notice this is the first byte of the driver. When you press SHIFT+F5 to ;to run in the environment, I believe QB copies the original .QLB file ;overtop of the old one(or something similar to that). If this does actually ;happen, and my play interrupt is in progress, all hell could break loose. ;Putting this flag first should protect against that (?)... EndFlag db 0 even ;Enables the driver. TweakOn proc far Push bp Mov bp, sp Push ds Push si ; si & di probably don't need to be Push di ; preserved for QB, but what the hell! Mov ax, cs Mov ds, ax Mov ax, 3508h ; Get interrupt 08h vector in es:bx Int 021h Mov dx, offset NewInterrupt Cmp bx, dx ; Has it already been changed? Jne NotInstalled ; Nope Mov ax, cs ; Check the segment Mov cx, es Cmp ax, cx ; Compare the segments Je ExitTweakOn ; If same then exit Even NotInstalled: Mov cx, [ss:bp+06] ; Get interrupt rate Cmp cx, 40000 ; < 1 or > 40000 ? Ja ExitTweakOn And cx, cx Jz ExitTweakOn Mov [ds:EndFlag], 0 ; Make sure interrupt doesn't play Mov [ds:IFreq], cx ; Save interrupt frequency for later Mov [ds:OldOfs], bx ; Save original interrupt 08h vector Mov [ds:OldSeg], es cli ; Disable interrupts Mov ax, 02508h ; Change interrupt 08h vector to my Int 021h ; routine Mov al, 00110110b ; Reprogram the 8253 timer chip Out 043h, al ;Masm 4.00 didn't like this: ;Mov dx, 1193180 shr 16 ;Mov ax, 1193180 and 0FFFFh Mov dx, 012h ; Find the correct delay value: Mov ax, 034DCh ; Delay = 1193180/Frequency Div cx Out 040h, al ; Send it Mov al, ah Out 040h, al In al, 061h ; Turn on PC-Speaker Or al, 3 Out 061h, al Mov al, 128+32+16 ; Reprogram high & low bytes to 0 Out 043h, al Xor al, al Out 042h, al Out 042h, al Mov al, 128+16 ; Tell 8253 we only want to change the Out 043h,al ; low byte for now on sti ; Let it lose! ExitTweakOn: Pop di ; Pop regs and exit to QB Pop si Pop ds Pop bp ret 2 TweakOn endp ; This is the PC-Speaker translation table. A simple XLAT statement ; will translate an 8-bit signed sample into the correct delay value ; for the 8253 timer. (See MAKESIGN.BAS to see how this table was made.) TweakTable: db 32,31,30,29,28,27,26,25,24,24,23,23,22,22,21,21,21,20,20,20,19,19,19 db 18,18,18,18,17,17,17,17,16,16,16,16,15,15,15,15,14,14,14,14,14,13,13 db 13,13,13,12,12,12,12,12,11,11,11,11,11,11,10,10,10,10,10,10,9,9,9,9 db 9,9,8,8,8,8,8,8,7,7,7,7,7,7,7,6,6,6,6,6,6,6,5,5,5,5,5,5,5,4,4,4,4,4 db 4,4,3,3,3,3,3,3,3,2,2,2,2,2,2,2,1,1,1,1,1,1,1,1,65,65,65,65,65,65,65 db 64,64,64,64,64,64,64,63,63,63,63,63,63,63,62,62,62,62,62,62,62,61,61 db 61,61,61,61,61,60,60,60,60,60,60,60,59,59,59,59,59,59,59,58,58,58,58 db 58,58,57,57,57,57,57,57,56,56,56,56,56,56,55,55,55,55,55,55,54,54,54 db 54,54,53,53,53,53,53,52,52,52,52,52,51,51,51,51,50,50,50,50,49,49,49 db 49,48,48,48,48,47,47,47,46,46,46,45,45,45,44,44,43,43,42,42,41,40,39 db 38,37,36,35,34,33 Even IFreq dw 65535 ; Original interrupt rate OldOfs dw 0 ; Old interrupt vector OldSeg dw 0 SampleOffset dw 0 ; Current offset SampleSegment dw 0 ; Current segment SampleEnd dw 0 ; End of sample StepRate dw 0 ; Step rate of sample, actually Step/256 OffsetRemainder db 0 ; Current offset remainder Even NewInterrupt proc far Push ax ; Save ax Cmp [cs:endflag], 0ffh ; Any samples to play? Je SamplesLeft ; Yup. Mov al, 020h ; Send End of Interrupt command Out 020h, al Pop ax ; Restore ax Iret ; Return to original program Even SamplesLeft: ; Samples are left Push ds ; Preserve what we use Push es Push si Push bx Mov ax, cs ; Set ds to cs Mov ds, ax Les si, dword ptr [ds:SampleOffset] ; Get current offset:segment Mov bx, offset TweakTable ; Prepare to translate Mov al, [es:si] ; Get sample ; Add this statement to play unsigned samples!! ;Add al, 128 Xlat ; Translate sample Out 042h, al ; Send it to the 8253 Xor ax, ax ; Add the step rate to the Mov bx, [ds:StepRate] ; offset Add [ds:OffsetRemainder], bl ; Adjust the remainder Mov al, bh ; Add whole portion+carry Adc si, ax Mov [ds:SampleOffset], si ; Save it Cmp si, [ds:SampleEnd] ; Are we too far? Jae EndOfSample ; Yup. ExitInterrupt: Pop bx ; Pop all regs and return Pop si Pop es Pop ds Mov al, 020h Out 020h, al Pop ax Iret Even EndOfSample: ; No more samples left Mov [ds:EndFlag], ah ; Fix flag Jmp short ExitInterrupt ; Jump back NewInterrupt endp Even PlaySound proc far ; Lets the interrupt ; play a sample ;Stack frame... ;PlaySound Offset%, Segment%, Length%, Frequency% ; 12 10 8 6 Push bp Mov bp, sp Push ds Push si Push di Mov ax, cs Mov ds, ax Mov ax, [ss:bp+06] ; Frequency in range? Cmp ax, 40000 Ja ExitPlaySound ; Nope And ax, ax Jz ExitPlaySound ; Nope Xor dx, dx ; Multiply frequency by 256 Mov dl, ah ; (shift it left 8 places) Mov ah, al Mov al, dh Div [ds:Ifreq] ; Divide it by the interrupt rate ; to find the step rate(which will ; actually be multiplied by 256) Cli ; Turn off interrupts Mov [ds:StepRate], ax ; Save the step rate Mov bx, [ss:bp+12] ; Save the offset and segment of sample Mov [ds:SampleOffset], bx Mov ax, [ss:bp+10] Mov [ds:SampleSegment], ax Add bx, [ss:bp+8] Mov [ds:SampleEnd], bx ; Save the end of the sample Mov [ds:OffsetRemainder], 0 ; Clear the remainder Mov [ds:EndFlag], 0ffh ; Let it rip! Sti ExitPlaySound: Pop di Pop si Pop ds Pop bp Ret 8 PlaySound endp Even TweakOff proc far ; Disables the driver. Push ds Mov ax, 03508h ; Check to make sure the interrupt Int 021h ; 08h vector is pointing to my routine Cmp bx, offset NewInterrupt Jne AlreadyChanged ; Nope Mov ax, cs Mov ds, ax ; ds = cs Mov bx, es Cmp ax, bx Jne AlreadyChanged ; Nope Cli ; Disable interrupts Mov al, 00110110b ; Reprogram the timer to 18.206hz Out 043h, al Xor al, al Out 040h, al Out 040h, al Lds dx, dword ptr [ds:OldOfs] ; restore the old vector Mov ax, 02508h Int 021h Sti ; Let the interrupts go In al, 061h ; Turn the speaker off And al, NOT 03h ; (should this be "And al, 254" ?) Out 061h, al AlreadyChanged: Pop ds ; All done or interrupt 08h vector Ret 0 ; isn't pointing to our routine TweakOff endp even TweakStatus proc far ; Checks the state of the sample Mov al, [cs:EndFlag] ; Get flag Cbw ; Make it a word Ret 0 ; Exit TweakStatus endp cseg ends end