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Author Topic: SEGE Genesis sample limit ?  (Read 104 times)

Offline RetrogamerFeminist

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SEGE Genesis sample limit ?
« on: September 08, 2017, 08:22:51 PM »
Hi  ;)! I don't know what is the SEGA Genesis's limit of sampling. It's limited by the memory but wich one ? The memory used by the soundchip is the z80's memory wich is limited at 8kb. But I'm not sure that the SEGA Genesis games are using the 8kb limit... When I tried to not go out of 8kb, I figured that I couldn't load a lots of samples, but Mega Turrican have a lot of samples with great sound quality ( 33khz for the snares ). So, is the sampling memory limited by the cartrige ? I know that SNES have a 64kb sampling limit.

PS: Apparently, most of the SEG Genesis games use 4bits samplse to reduce their memorie, but I don't find any software where I can down the bits under 8
« Last Edit: September 08, 2017, 08:30:51 PM by RetrogamerFeminist »

Offline marcb0t

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SEGE Genesis sample limit ?
« Reply #1 on: September 14, 2017, 09:36:26 PM »
Hi  ;)! I don't know what is the SEGA Genesis's limit of sampling. It's limited by the memory but wich one ? The memory used by the soundchip is the z80's memory wich is limited at 8kb. But I'm not sure that the SEGA Genesis games are using the 8kb limit... When I tried to not go out of 8kb, I figured that I couldn't load a lots of samples, but Mega Turrican have a lot of samples with great sound quality ( 33khz for the snares ). So, is the sampling memory limited by the cartrige ? I know that SNES have a 64kb sampling limit.

PS: Apparently, most of the SEG Genesis games use 4bits samplse to reduce their memorie, but I don't find any software where I can down the bits under 8

Sega Genesis streams samples through the DAC on the ym2612 chip. It can stream samples up to a quality of 8-bit/32Khz (possibly higher).
I imagine if you were to force a sample of an unusually high sample rate of 88, 96, or 192KHz, then you would have memory bottle necking, skipping, and delayed playback issues. But that would be the case for any modern sound system as well.

Fortunately, anything beyond 32Khz is unneccessary, and a waste of ROM space. I'd settle for 22K or 32K for high quality samples. It's possible to get decent stuff with 8 and 11Khz as well, if you convert and anti-alias your samples right.

To answer your question, samples are loaded from the ROM to the DAC. You can fill up a 4MB cartridge with samples and no game data, if you want. And you would still be able to play each sample one at a time at the highest 32Khz setting.

If you multi track samples through the DAC, like triggering 4 or 8 samples through the DAC at a time (this IS possible)... Then you will probably run into conflicts eventually depending on the size, quality of your samples. I could be wrong, but I'm pretty certain that the sound RAM of 8KB starts getting filled up pretty quick.

But streaming one sample at a time at highest quality, you shouldn't have a problem.

Hope this answers your question.

Offline Ozaleto

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SEGE Genesis sample limit ?
« Reply #2 on: September 15, 2017, 04:39:01 PM »
Quote
Sega Genesis streams samples through the DAC on the ym2612 chip. It can stream samples up to a quality of 8-bit/32Khz (possibly higher).

Actually, it can't go to 32kHz on hardware. You will start missing writes to the DAC at half of the sample rate (~26kHz) that the YM2612 has (~53kHz) when it goes through the main DAC that makes the output analog. DefleMask and emulation seems to play it just 32kHz fine but on hardware it starts to be very noticeable. It is recommended that if you want max performance from the DAC that you should use 8-bit 26kHz samples.
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Offline marcb0t

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SEGE Genesis sample limit ?
« Reply #3 on: September 19, 2017, 04:56:11 PM »
Quote
Sega Genesis streams samples through the DAC on the ym2612 chip. It can stream samples up to a quality of 8-bit/32Khz (possibly higher).

Actually, it can't go to 32kHz on hardware. You will start missing writes to the DAC at half of the sample rate (~26kHz) that the YM2612 has (~53kHz) when it goes through the main DAC that makes the output analog. DefleMask and emulation seems to play it just 32kHz fine but on hardware it starts to be very noticeable. It is recommended that if you want max performance from the DAC that you should use 8-bit 26kHz samples.
Well, Ozaleto, thank you for the heads up. I personally did not realize that 32kHz would start missing writes that would cause a noticeable effect on hardware. I remember hearing something like that from Tiido, but did not understand how that sounds in practice.

Yeah, hardware is always the "gold standard" of chiptune playback. So frankly, I might want to downscale all my sampling to at most 22kHz.

For making music for the Echo sound driver, it's best to pre-scale your samples down to 10,650Hz, which seems to be a weird sample rate. But it just works out better since Echo automatically converts samples to that anyway.

Obviously, for best sound in a Deflemask module, import every sample as a 16-bit mono sample. Deflemask automatically converts it to 8-bit playback, and you can raise the AMP of each sample without the nasty clicking and clipping.

When designing for Echo sound driver, you WILL need to downconvert to 8-bit, actually. Really just depends on what you're going for.

Offline RetrogamerFeminist

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SEGE Genesis sample limit ?
« Reply #4 on: September 22, 2017, 06:01:41 PM »
Thanks, but if I understand, the samples is loaded on the RAM just while playing it then it's deloaded ? But why on SNED are the samples compressed tout size on 64kb ?