Author Topic: Some audio stuffs  (Read 3428 times)

Bonknuts

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Some audio stuffs
« on: October 31, 2015, 07:39:46 AM »
I posted here: https://pcedev.wordpress.com/2015/10/31/pcm-player/

tl;dr
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On the topic of audio, have you guys ever heard the PCE stream 55khz 5bit PCM using the channel’s waveform memory as a buffer? Check it out: http://pcedev.net/6280a/sgx_dump.wav   That was recorded from my SuperGrafx.


 So, basically I know what I can do on the SGX or more specifically the 6280a, but I wanted to get some recordings from PCE owners (6280), if possible. I'll post a few demos. I'm looking for recordings like the one above and what console it was recorded from.

touko

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Re: Some audio stuffs
« Reply #1 on: October 31, 2015, 10:47:08 AM »
Great, i always wanted to know what's the max PCE's frequency for PCM ..
55khz is awesome, but i think (even if it's useless) it could be higher ??

Bonknuts

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Re: Some audio stuffs
« Reply #2 on: October 31, 2015, 11:28:05 AM »
Supposedly, up to 3.5mhz if you can write to it that fast - lol. With a 7khz interrupt, you can output 224khz if you use all 32 bytes in the waveform buffer.

elmer

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Re: Some audio stuffs
« Reply #3 on: October 31, 2015, 12:18:56 PM »
I posted here: https://pcedev.wordpress.com/2015/10/31/pcm-player/

Cool stuff!  :)

I'm definitely curious to hear something that takes advantage of all those capabilities.

IIRC, the typical CPU budget for sound/music on home-computers was around the 10%-15% range.


With a 7khz interrupt, you can output 224khz if you use all 32 bytes in the waveform buffer.

Music for bats?  :wink:

touko

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Re: Some audio stuffs
« Reply #4 on: November 01, 2015, 01:02:08 AM »
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224khz
whow, i think a NG cartridge is needed .

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Music for bats?  :wink:
:lol:


pceslayer

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Re: Some audio stuffs
« Reply #5 on: November 05, 2015, 10:21:57 AM »
What would be the best way to record the samples? RCA -> 3.5mm into aux input?

I have quite a few variations of PCE/TG hardware I can test with.

spenoza

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Re: Some audio stuffs
« Reply #6 on: November 05, 2015, 10:28:06 AM »
I'm still clueless as to why they put the 6280a in the Core, but not in any of the other PCE systems. Any thoughts?
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Black Tiger

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Re: Some audio stuffs
« Reply #7 on: November 05, 2015, 11:02:54 AM »
I'm still clueless as to why they put the 6280a in the Core, but not in any of the other PCE systems. Any thoughts?

Same reason the SuperGrafx (which also has it) wasn't supported. The PCE as it was, was already good enough and proved it by going the distance.
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spenoza

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Re: Some audio stuffs
« Reply #8 on: November 05, 2015, 12:31:47 PM »
I'm still clueless as to why they put the 6280a in the Core, but not in any of the other PCE systems. Any thoughts?

Same reason the SuperGrafx (which also has it) wasn't supported. The PCE as it was, was already good enough and proved it by going the distance.

Except that the improvements in the 6280a are minor enough that I doubt they increased production cost, and they clearly already had the ability to manufacture the chips. That's why I'm confused. It seems like it should have been one of those seamless upgrades nobody would have noticed.
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Black Tiger

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Re: Some audio stuffs
« Reply #9 on: November 05, 2015, 12:59:41 PM »
Just read the blog post. 29% cpu resource for 4 XM channels is pretty amazing since Air Zonk does everything it does with 21% wasted on audio. I'm guessing that 6 channels would be fine running with most sections of an RPG.
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touko

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Re: Some audio stuffs
« Reply #10 on: November 05, 2015, 07:29:06 PM »
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since Air Zonk does everything it does with 21% wasted on audio.
Yes airzonk's driver sucks .
I have a driver with compression/buffering and banking it uses 3/4% per channel .

ccovell

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Re: Some audio stuffs
« Reply #11 on: November 05, 2015, 08:54:07 PM »
Yes airzonk's driver sucks .
I have a driver with compression/buffering and banking it uses 3/4% per channel .
Doesn't 3%-4% x 6 mean 18%-24%?

touko

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Re: Some audio stuffs
« Reply #12 on: November 05, 2015, 10:27:00 PM »
Deleted
« Last Edit: November 05, 2015, 11:46:11 PM by touko »

Bonknuts

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Re: Some audio stuffs
« Reply #13 on: November 06, 2015, 03:28:11 AM »
Just read the blog post. 29% cpu resource for 4 XM channels is pretty amazing since Air Zonk does everything it does with 21% wasted on audio. I'm guessing that 6 channels would be fine running with most sections of an RPG.

 Airzonk is a lot higher than 21% cpu resource. Just to be sure, before posting this reply, I took 10 readings from the game's TIMER interrupt. The actual cpu resource floats between 29% and 33%.

It was at 33% when it had to reload the bit shifter (decompress the samples), which if I recall is every three samples or so. It was about 30% for just playing the sample. That doesn't include any music engine stuff (reading the byte code music for the normal channels). I made sure the samples (sampling of the code) I read didn't touch that part (that would give a false reading). So 30% just for playing the samples, and whatever cpu resource for regular channels.

 For an RPG, I think you could get away with almost 70% cpu resource dedicated for audio (if the game is coded in assembly). That would allow much higher rate sampled channels. 
« Last Edit: November 06, 2015, 03:31:18 AM by Bonknuts »

Black Tiger

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Re: Some audio stuffs
« Reply #14 on: November 06, 2015, 03:47:12 AM »
So that adpcm player you posted a video of playing that Mega Man cover would be doable cpu-wise in an RPG then? It'd be a cool way to do snippets of voice acting in cinemas (which I assume are even less intensive) or for repetitive bgms.

It's crazy to think that ineficient sound alone in Air Zonk eats up at least a third of cpu resource when it throws around as much as it does compared to SNES and Genesis shooters.
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