A 5th Audio Channel on the Amiga

Mrs Beanbag · 13 August 2016, 22:08

ok so someone plugged his Amiga's composite out signal into an amp and played samples over it by drawing on the screen

http://jmp.no/blog/a-5th-audio-channel-on-the-amiga

Amiga1992 · 13 August 2016, 22:47

Yeah nice, this is possible with any machine that outputs composite.
Here's a C64 demo that did this a long while ago using VIC noise:

[ Show youtube player ]

Retro1234 · 14 August 2016, 11:04

Can you have anything on screen but static?

Mrs Beanbag · 14 August 2016, 23:20

if you were clever perhaps you could put something else on the screen, maybe using colour, i don't know... the C64 video posted above also has a scroller across the middle. The problem is it's the pattern on the screen that produces the sound. Then again if you were using something like Indivision or the HDMI output of the Vampire accelerator you could still output this stuff to composite while displaying something else independently on the other output (?)

Retro1234 · 15 August 2016, 00:19

Maybe you can have something on both RTG and normal display?

Amiga1992 · 15 August 2016, 17:34

I thought you couldn't have RTG and standard display at once.

Thorham · 15 August 2016, 18:46

Interesting hack. Too bad it's not useful.

Daedalus · 16 August 2016, 09:58

The OS doesn't support using both at once, but there's no technical reason I can think of that you can't bang the hardware directly to get output on the native screen.

pandy71 · 16 August 2016, 18:53

Quote:

Originally Posted by Mrs Beanbag

ok so someone plugged his Amiga's composite out signal into an amp and played samples over it by drawing on the screen

http://jmp.no/blog/a-5th-audio-channel-on-the-amiga

I have better hack for you - use 4 bit TTL output from video port in same way as DCTV or HAM-E or similar.
Code PCM on video then collect data - you can realtively easy output 16 bit stereo PCM 48kHz even on naked A500 in such way - this can be done with simple state machine on few TTL circuits, on hires line (640 pixels) 320 bytes can be coded so single line can cary 16000 bytes per second to feed 48000 16 bit stereo you need 12 hires lines - this area can be masked in TTL logic to avoid visible garbage...

Mrs Beanbag · 17 August 2016, 23:15

i did wonder today about using sprites instead of copper palette changes to achieve the effect. so one could render samples into sprites and play with 8 channels by putting the sprites in different places! (Maybe repeating them across the screen to increase the loudness)

13 August 2016, 22:08	#1
Mrs Beanbag Glastonbridge Software Join Date: Jan 2012 Location: Edinburgh/Scotland Posts: 2,243	A 5th Audio Channel on the Amiga ok so someone plugged his Amiga's composite out signal into an amp and played samples over it by drawing on the screen http://jmp.no/blog/a-5th-audio-channel-on-the-amiga

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13 August 2016, 22:47	#2
Amiga1992 Registered User Join Date: May 2001 Location: ? Posts: 19,644	Yeah nice, this is possible with any machine that outputs composite. Here's a C64 demo that did this a long while ago using VIC noise: [ Show youtube player ]

14 August 2016, 11:04	#3
Retro1234 Phone Homer Join Date: Jun 2006 Location: 5150 Posts: 5,773	Can you have anything on screen but static?

14 August 2016, 23:20	#4
Mrs Beanbag Glastonbridge Software Join Date: Jan 2012 Location: Edinburgh/Scotland Posts: 2,243	if you were clever perhaps you could put something else on the screen, maybe using colour, i don't know... the C64 video posted above also has a scroller across the middle. The problem is it's the pattern on the screen that produces the sound. Then again if you were using something like Indivision or the HDMI output of the Vampire accelerator you could still output this stuff to composite while displaying something else independently on the other output (?)

15 August 2016, 00:19	#5
Retro1234 Phone Homer Join Date: Jun 2006 Location: 5150 Posts: 5,773	Maybe you can have something on both RTG and normal display?

15 August 2016, 17:34	#6
Amiga1992 Registered User Join Date: May 2001 Location: ? Posts: 19,644	I thought you couldn't have RTG and standard display at once.

15 August 2016, 18:46	#7
Thorham Computer Nerd Join Date: Sep 2007 Location: Rotterdam/Netherlands Age: 47 Posts: 3,751	Interesting hack. Too bad it's not useful.

16 August 2016, 09:58	#8
Daedalus Registered User Join Date: Jun 2009 Location: Dublin, then Glasgow Posts: 6,334	The OS doesn't support using both at once, but there's no technical reason I can think of that you can't bang the hardware directly to get output on the native screen.

17 August 2016, 23:15	#10
Mrs Beanbag Glastonbridge Software Join Date: Jan 2012 Location: Edinburgh/Scotland Posts: 2,243	i did wonder today about using sprites instead of copper palette changes to achieve the effect. so one could render samples into sprites and play with 8 channels by putting the sprites in different places! (Maybe repeating them across the screen to increase the loudness)

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