PCM samples

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By Daemos

Paragon (2044)

Daemos's picture

08-04-2014, 22:11

Quote:

You could have samples at specific moments when it’s ok to pause the visuals… like “it’s a-me, mario” after you press start at the title screen, or a sample when you die or you’ve completed the level. Could even play them on the PSG then. (Like Oh Shit Smile.)

I was just brainstorming on the possibilities of PCM usage but the turbo PCM is far too primitive to be used for high quality sampling. Using it as small samples in motion stopped screens is not worth the effort honestly to implement. I was hoping for supernes like sounds but this PCM is not the same (what was I thinking).

Intruder is awesome btw!

By Manuel

Ascended (19273)

Manuel's picture

08-04-2014, 22:59

And in the No Waste demo by Xelasoft? (It plays a 4 channel MOD file on the turboR PCM while showing a scroll...)

By Grauw

Ascended (10699)

Grauw's picture

08-04-2014, 23:32

When playing back at 22kHz, there’s about 160 Z80 cycles between every sample byte output (and a bunch more on R800). A scroll is just a big copy command and a smaller one, it can be interleaved with sample playback relatively easily and then the VDP will handle the rest of it… Just like that demo is apparently also interleaving the MOD processing and channel mixing.

Interleaving is fine for demos and replayers, code can be written especially to fit in these small chunks between sample outputs. However for background playback in games… well theoretically it could be done if the game was designed for it from the ground up, but it’s not very practical…

By syn

Prophet (2113)

syn's picture

10-04-2014, 01:53

I was just wondering, do the difficulties Grauw described in his post regarding sample playback during gameplay apply to the other known methods (besides obviously msx audio and moonsound)? like for example what Artrag showed in that intruder demo? Or does the SCC work different in this regard?

@artrag I was impressed with your techdemo of some other game with samples on youtube (I forgot the name, it was some multidirectional shooter).. good job on that.

Also I don't think zone terra's sound fx sound that bad.. it just lacks a bit in the higher frequencies... maybe they used terrible source material?

By ARTRAG

Enlighted (6923)

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10-04-2014, 06:35

scc has a 128 byte buffer that can be used to play samples from the standard irs at vblank
the sampling frequency will be 128x60 =7680 Hz at the same cpu cost of a normal pt3 player

By Daemos

Paragon (2044)

Daemos's picture

10-04-2014, 08:17

Quote:

scc has a 128 byte buffer that can be used to play samples from the standard irs at vblank
the sampling frequency will be 128x60 =7680 Hz at the same cpu cost of a normal pt3 player

Only because of that, SCC is very usefull for fairly detailed sfx sampling. The only thing about SCC is the type of distinct sound it plays. It has this fairly harsh character to it. This sounds awesome and fitting in high speed hard action games but it doesn't sound smooth and friendly enough for smooth colorfull games. PCM appears very bassy. I am missing higher notes. However the harsh sound is less. PSG sounds very highly pitched.

By ARTRAG

Enlighted (6923)

ARTRAG's picture

10-04-2014, 09:08

The fact you have in my tests low frequency sounds is due to the sampling frequency that cannot be chosen freely and that on NTSC machines is 128*60 = 7680Hz but on PAL is just 128*50 = 6400Hz.
The true limit to the use of this solution is the noise that the actual device will add to the samples due to an HW bug of the chip that gives a sort of spikes each time the cpu accesses to its registers.
I wouldn't play music with this technique, anyway, for sampled voice and normal sfx (explosions or other sounds) it is fairly usable.

http://www.youtube.com/watch?v=0PRDKrT7VsM

By Daemos

Paragon (2044)

Daemos's picture

10-04-2014, 10:20

Are the the SFX when hit by some object also SCC?

By ARTRAG

Enlighted (6923)

ARTRAG's picture

10-04-2014, 18:25

yes

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