How to stop sample playback ?

AmiGer · 09 December 2004, 09:23

Hi,

when playing a sound sample with direct hardware programming (e.g. in assembler) the sample is looped by default. What's the best way to stop the playback after it was played once (e.g.interrupt?) ?

Any examples ?

girv · 09 December 2004, 10:23

Yes, the best way is to wait for the audio interrupt then stop DMA for the channel. I also set its volume to zero but I'm not sure if that is strictly necessary

AmiGer · 09 December 2004, 18:48

Well, I assumed that but when I try to setup an interrupt then it is called immediately after I enabled it.
So maybe you or anybody have an example or any tips how to set up and code the interrupt routine correctly ?
Thanks.

girv · 10 December 2004, 10:26

I've got some asm examples in the form of a simple sound effects engine for a game. I'll try to extract the source over the weekend - its on a backup CD somewhere in the computer graveyard that is our back room

AmiGer · 10 December 2004, 13:13

That would be very nice... I experimented a little bit but still have problems...

Photon · 11 December 2004, 01:46

Have you looked at one of the playroutines for a tracker, like Noisetracker?

What you usually do is to wait at least 4 raster lines, then set the audio pointers and loops to whatever you want. It will then take effect when the sound reaches the end. This means that you can start a sound with any loop length (AUDxLEN) you want. When the sound is to stop, you set the sound pointer to a word that is 0 (to avoid clicks) and set the AUDxLEN (loop) to 1.

If you start sounds at a specific point in time, like waiting for VBLANK, it's easier to use some sort of timing to wait at least 4 raster lines instead of using the audio interrupt, like the copper (which I use). I just poke the correct values into the copper list and the copper moves them into the sound registers when the time comes.

The protracker playroutine uses a cheap timer interrupt wait loop to do it:
STARTSOUND:
MOVE.W n_dmabit(A6),$DFF096 ;Audio DMA off
MOVE.L n_start(A6),(A5) ;Set sampledata pointer
MOVE.W n_length(A6),4(A5) ;Set length
MOVE.W n_period(A6),6(A5)
MOVEQ #0,D0
MOVE.B n_volume(A6),D0

move.b pt_timeout,$bfe701 ;TimerB HI
move.b pt_timeout+1,$bfe601 ;TimerB LO
move.b #%000011001,$bfef01 ;set commandbits: OneShot & CLK & Start
WAIT1:
pt_timerwait3
btst #0,$bfef01 ;timeout on timerB? (ICR TimerB)
bne.s pt_timerwait3 ;nope...
STARTIT:
MOVE.W n_dmabit(A6),D0
BSET #15,D0
MOVE.W D0,$DFF096

WAIT2:
move.b pt_timeout,$bfe701 ;TimerB HI
move.b pt_timeout+1,$bfe601 ;TimerB LO
move.b #%000011001,$bfef01 ;set commandbits: OneShot & CLK & Start
pt_timerwait4
btst #0,$bfef01 ;timeout on timerB? (ICR TimerB)
bne.s pt_timerwait4 ;nope...

STOPIT:
MOVE.L n_loopstart(A6),(A5) ;SET TO POINT TO A 0 WORD
MOVE.L n_replen(A6),4(A5) ;SET TO 1
pt_rtnend

Hope this helps.

AmiGer · 11 December 2004, 10:44

Yes, I had a look at a lot of tracker playback routines and I was very surprised that it is such "complicated" to do an easy sample playback. Anyway my program works now and your example is very helpful, thanks.

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09 December 2004, 09:23	#1
AmiGer Registered User Join Date: Sep 2002 Location: Germany Posts: 349	How to stop sample playback ? Hi, when playing a sound sample with direct hardware programming (e.g. in assembler) the sample is looped by default. What's the best way to stop the playback after it was played once (e.g.interrupt?) ? Any examples ?

09 December 2004, 10:23	#2
girv Mostly Harmless Join Date: Aug 2004 Location: Northern Ireland Posts: 1,115	Yes, the best way is to wait for the audio interrupt then stop DMA for the channel. I also set its volume to zero but I'm not sure if that is strictly necessary

09 December 2004, 18:48	#3
AmiGer Registered User Join Date: Sep 2002 Location: Germany Posts: 349	Well, I assumed that but when I try to setup an interrupt then it is called immediately after I enabled it. So maybe you or anybody have an example or any tips how to set up and code the interrupt routine correctly ? Thanks.

10 December 2004, 10:26	#4
girv Mostly Harmless Join Date: Aug 2004 Location: Northern Ireland Posts: 1,115	I've got some asm examples in the form of a simple sound effects engine for a game. I'll try to extract the source over the weekend - its on a backup CD somewhere in the computer graveyard that is our back room

10 December 2004, 13:13	#5
AmiGer Registered User Join Date: Sep 2002 Location: Germany Posts: 349	That would be very nice... I experimented a little bit but still have problems...

11 December 2004, 01:46	#6
Photon Moderator Join Date: Nov 2004 Location: Eksjö / Sweden Posts: 5,613	Have you looked at one of the playroutines for a tracker, like Noisetracker? What you usually do is to wait at least 4 raster lines, then set the audio pointers and loops to whatever you want. It will then take effect when the sound reaches the end. This means that you can start a sound with any loop length (AUDxLEN) you want. When the sound is to stop, you set the sound pointer to a word that is 0 (to avoid clicks) and set the AUDxLEN (loop) to 1. If you start sounds at a specific point in time, like waiting for VBLANK, it's easier to use some sort of timing to wait at least 4 raster lines instead of using the audio interrupt, like the copper (which I use). I just poke the correct values into the copper list and the copper moves them into the sound registers when the time comes. The protracker playroutine uses a cheap timer interrupt wait loop to do it: STARTSOUND: MOVE.W n_dmabit(A6),$DFF096 ;Audio DMA off MOVE.L n_start(A6),(A5) ;Set sampledata pointer MOVE.W n_length(A6),4(A5) ;Set length MOVE.W n_period(A6),6(A5) MOVEQ #0,D0 MOVE.B n_volume(A6),D0 move.b pt_timeout,$bfe701 ;TimerB HI move.b pt_timeout+1,$bfe601 ;TimerB LO move.b #%000011001,$bfef01 ;set commandbits: OneShot & CLK & Start WAIT1: pt_timerwait3 btst #0,$bfef01 ;timeout on timerB? (ICR TimerB) bne.s pt_timerwait3 ;nope... STARTIT: MOVE.W n_dmabit(A6),D0 BSET #15,D0 MOVE.W D0,$DFF096 WAIT2: move.b pt_timeout,$bfe701 ;TimerB HI move.b pt_timeout+1,$bfe601 ;TimerB LO move.b #%000011001,$bfef01 ;set commandbits: OneShot & CLK & Start pt_timerwait4 btst #0,$bfef01 ;timeout on timerB? (ICR TimerB) bne.s pt_timerwait4 ;nope... STOPIT: MOVE.L n_loopstart(A6),(A5) ;SET TO POINT TO A 0 WORD MOVE.L n_replen(A6),4(A5) ;SET TO 1 pt_rtnend Hope this helps.

11 December 2004, 10:44	#7
AmiGer Registered User Join Date: Sep 2002 Location: Germany Posts: 349	Yes, I had a look at a lot of tracker playback routines and I was very surprised that it is such "complicated" to do an easy sample playback. Anyway my program works now and your example is very helpful, thanks.

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