PSG channel count vs. features

[grml]

I have been looking at the specs for the PSG and scratching my head for a while: we'll get 16(!) channels for beeps and boops, but no envelopes, and no filters either?

Am I the only one seeing a weird feature disparity here - who needs 16 channels of pure beeps and boops? Having more features per channel would improve the quality of the sound even if it came at the cost of fewer sound channels, right?

I guess it's really difficult to implement those things that I think made the SID great? It was 3 channels of awesomeness - I would like to have some of that awesomeness, and I don't even need 16 channels of it.

Edit: I think I chose the wrong subforum for this, and it also may come off a bit more critical than intended. I was *slightly* drunk when I wrote it last night. I just want to know what you guys think about the lack of envelopes and filters in the PSG.

[kelli217]

You mean filters, and envelopes, and ring modulation? Yeah, we know. It's being looked into for a third-party solution.

[Edmond D]

For us with low to no musical talent and started with a VIC-20 having the three different sound systems (VERA PSG & PCM and the YM2151) seems to be more than enough for me. I can see that perhaps coming from the C64 and having some musical talent those people will feel the X16 PSG is not as good.  Given the X16 has expansion cards allows the base system to be extended, I feel that those who are talented will create an option that works for  their needs. 

BTW - I'd like to see a "X16 Sound for the Tone Deaf" FAQ explaining how everything fits together and can be used. 

 

[grml]

On 12/6/2022 at 8:30 PM, Edmond D said:

For us with low to no musical talent and started with a VIC-20 having the three different sound systems (VERA PSG & PCM and the YM2151) seems to be more than enough for me.

It's not a question of quantity. 16 sound generator channels is more than enough, it's just that they are not very expressive without envelopes and filters. It's like having stupidly high resolution graphics but no colors.

Envelopes can be simulated in software to a degree at least, but the lack of filters is unfortunate. The SID in the C64 would have been totally unremarkable if it wasn't for the filter (and ring modulators, as kelli has mentioned), and the VERA PSG is totally unremarkable for this very reason.

Eh, I guess I'm late to the party for this discussion ?

[Edmond D]

On 12/7/2022 at 3:07 AM, grml said:

t's not a question of quantity. 16 sound generator channels is more than enough, it's just that they are not very expressive without envelopes and filters. It's like having stupidly high resolution graphics but no colors.

Thanks for the analogy, as I have very little background in sound generation. Not sure what an envelope (or ring modulator) is or how filters are used, so not knowing what they are or how they applied means I don't know what I'm missing. Perhaps if I heard examples of sounds without then with these items I might clue in. Perhaps a simple short video using some sound system that has these features would help.



There is a new thread starting on sound here which might help me understand. Thoughts?


 

On 12/7/2022 at 3:07 AM, grml said:

Eh, I guess I'm late to the party for this discussion ?

Perhaps for the initial release. I believe the VERA module design & details will be made open source at some point, which would allow those in the know and have the talents to create a VERA II hardware unit that has new features, both in sound and graphics..  The other option mentioned was an expansion card. The X16 was designed to be a hobbyist computer that could be modified and extended rather than a closed system.

[ZeroByte]

My $0.02's worth on 16 channels: VERA's lack of filters, ADSR envelopes, etc make it less SID-like, but having this many channels gives it its own unique identity vs the PSG chips of old. Having this many voices gives you a lot of nice synth-like functionality by using multiple channels as a single instrument. That's the core concept for Concerto, which makes some really awesome-sounding stuff.

I mean, who wouldn't want to have some fun with 2 channels of 8-voice supersaw? ?

 

[Wavicle]

On 12/3/2022 at 3:29 PM, grml said:

I have been looking at the specs for the PSG and scratching my head for a while: we'll get 16(!) channels for beeps and boops, but no envelopes, and no filters either?



Am I the only one seeing a weird feature disparity here - who needs 16 channels of pure beeps and boops? Having more features per channel would improve the quality of the sound even if it came at the cost of fewer sound channels, right?



I guess it's really difficult to implement those things that I think made the SID great? It was 3 channels of awesomeness - I would like to have some of that awesomeness, and I don't even need 16 channels of it.



Edit: I think I chose the wrong subforum for this, and it also may come off a bit more critical than intended. I was *slightly* drunk when I wrote it last night. I just want to know what you guys think about the lack of envelopes and filters in the PSG.

To my knowledge, implementing sound envelopes in digital logic requires a multiplier. A 16-bit integer multiplier will probably do fine. However, when it comes to FPGAs, implementing a multiplier is extremely expensive. For that reason many FPGAs, including the iCE40UP5K used for VERA, will have hard IP multipliers to avoid large chunks of the floorplan being dedicated to an otherwise small circuit. When I started working on and supporting VERA, all of the hardware multipliers in the FPGA were used. I had said as much in this message back in June when discussing alpha blending: 


That said, for reasons unclear to me, somewhere in the shuffle of all of the fixes and timing improvements I had implemented for VERA between June and October, the synthesizer began reporting that only 5 of 8 multipliers were being used. I don't know if I was mistaken back then (I doubt it), and I cannot think of a change I had made during that time which would reduce the number of multipliers in use. My best guess is that one of the optimizer hints that I had added allowed the synthesizer to infer and allocate a 16bit multiplier as two 8bit multipliers. I'm honestly not sure. In theory, there are enough resources now to add envelope support, but in reality it's pretty late to be adding in something like this. It would require a lot of register support and at this point every register added comes at the cost of VRAM. It could also break existing applications that use the top of VRAM for display or sprite data.

[rje]

On 12/7/2022 at 5:07 AM, grml said:

It's not a question of quantity. 16 sound generator channels is more than enough, it's just that they are not very expressive without envelopes and filters. It's like having stupidly high resolution graphics but no colors.



Envelopes can be simulated in software to a degree at least, but the lack of filters is unfortunate. The SID in the C64 would have been totally unremarkable if it wasn't for the filter (and ring modulators, as kelli has mentioned), and the VERA PSG is totally unremarkable for this very reason.



Eh, I guess I'm late to the party for this discussion ?

 

Well, without envelopes, the PSG is almost useless.

Doesn't matter how late you are;  I've grumbled about this periodically for a couple years.  It's not a priority.

Experts at this kind of thing just pull their own code to do what they need to do -- and typically they'll use the YM chip instead of the PSG.

 

I'm not sure who the PSG is there for.  It's not there for me.  With no envelope, it means you have to write your own interrupt-driven envelope thingy.  I don't seem to have that sort of energy, so the stuff I write doesn't have useful sound.

 

The YM, meanwhile, might be useful by me; it has envelopes.  But since I've never used it, I'll first have to learn how to use it by trial and error.