Just a test (Realtime Convolution)

[matti]

I wanted to test out a theory.. and it seemed to work alright.

Realtime Convolution with SM -> download a vst

Yep, that's right, there's no latency.
But there are few drawbacks:
- High cpu usage
- Only 2048 sample mono Impulse Responses
(loads stereo files too, but won't use the stereo information)

Good things:
- Zero latency convolution
- Loads Wav files
- Resampling of the IR's if needed
- Stereo processing (two channels processed with the same IR)
- Graph of the frequency response(blue for the 2048 sample, red for the original n-sample)
- Graph of the phase response(orange)

Consider this a tech demo, nothing more..

Be carefull when loading IR files!

[infuzion]

Wow!
Let me know if you want some ASM help here...

[aliasant]

Very cool. It wouldnt accept any of my IR files but it did work with a mono wave audiotrack that I have for test purposes.
That was about a minute of audio but I guess it just took the 2048 first sampels of that ?

You should sell this to Malc =)

[matti]

Yes it takes the 2048 first samples.

I don't think there's any "real" applications for this. The CPU usage is just too high. There are some things i could try that might help my 3ghz P4 to run 8192 sample stereo impulses(in theory it could work), but that's still not much, and it would eat up all the power. I think i should try if this works better with C++/asm...

[aliasant]

Yes it takes the 2048 first samples.

I don't think there's any "real" applications for this. The CPU usage is just too high. There are some things i could try that might help my 3ghz P4 to run 8192 sample stereo impulses(in theory it could work), but that's still not much, and it would eat up all the power. I think i should try if this works better with C++/asm...

Well If your building a amp simulator or something else you dont need long impulses. Same if you want to simulate a filter.
Doing that you need very small impulses and maybe 2048 is just enough for that?

[TomC]

Yes it takes the 2048 first samples.

I don't think there's any "real" applications for this. The CPU usage is just too high. There are some things i could try that might help my 3ghz P4 to run 8192 sample stereo impulses(in theory it could work), but that's still not much, and it would eat up all the power. I think i should try if this works better with C++/asm...

Well If your building a amp simulator or something else you dont need long impulses. Same if you want to simulate a filter.
Doing that you need very small impulses and maybe 2048 is just enough for that?

Yeah, but 2048 is too short, it'll be 1/20 sec @ 44.1 kHz.

I did a convolution module some months ago (probably a similar algorithm) and decided it's not worth my time to investigate further as long as there are no proper primitives available in SM.

It works, but it's like stabbing yourself to death with a Swiss army knife: it's possible, but the fun wears out after a couple of stitches...

Tom

[matti]

Yes it takes the 2048 first samples.

I don't think there's any "real" applications for this. The CPU usage is just too high. There are some things i could try that might help my 3ghz P4 to run 8192 sample stereo impulses(in theory it could work), but that's still not much, and it would eat up all the power. I think i should try if this works better with C++/asm...

Well If your building a amp simulator or something else you dont need long impulses. Same if you want to simulate a filter.
Doing that you need very small impulses and maybe 2048 is just enough for that?

Well.. yes i suppose so. Anyone thinking of building one btw? It would help in defining the needs for this convolution effect. If i would keep it down to 2048 samples i think i could squeeze a bit off the cpu usage. Making a mono version would also slice off half of the cpu usage..

Btw. i tested this myself with analog mixing console impulses. 2048 was just enough to get some of them to work properly. With longer impulses it ofcourse lost some of the content.

[aliasant]

I would love to put some of that in my effects.
Impuses are easy to find and there are plenty out there that sounds great.
Very nice in any vst effect. What it needs to have is a way to store more then 1 impulse.
Do you load them like any wave file? If so thats not a problem.
One could have a set of favorite impulses that the user can select from.
No need for the user to try and find impulses of his own.

[matti]

Yes they are like normal wave files.. So selectable impulses(basicly on the fly) could be possible. There are just alot of problems in how SM works to get them running smoothly. For example getting the array values to the code efficiently (now i basicly just have 2048 inputs in it )

[aliasant]

Yes they are like normal wave files.. So selectable impulses(basicly on the fly) could be possible. There are just alot of problems in how SM works to get them running smoothly. For example getting the array values to the code efficiently (now i basicly just have 2048 inputs in it )

OK. So how many cycles does one mono instance use?

[matti]

Yes they are like normal wave files.. So selectable impulses(basicly on the fly) could be possible. There are just alot of problems in how SM works to get them running smoothly. For example getting the array values to the code efficiently (now i basicly just have 2048 inputs in it )

OK. So how many cycles does one mono instance use?

It seems there's no way to benefit from the SIMD structure in SM with this schematic. There just isn't a way to get the data inside the code modules to be efficient enough. So basicly doing mono is not a viable solution after all. And to answer your question: one mono instance uses as much as 4 identical mono instances(packed stream). The vst in the link is basicly a mono instance. In a modular host using it with mixing desk(or eq, or similar short IR) emulation this might not be a problem, as you get 4 channels(with the same IR tho) with the price of one. All in all, i think this might already be as efficient as it possibly can

[infuzion]

It seems there's no way to benefit from the SIMD structure in SM with this schematic. There just isn't a way to get the data inside the code modules to be efficient enough

I know some ASM-fu that might help with that

[matti]

It seems there's no way to benefit from the SIMD structure in SM with this schematic. There just isn't a way to get the data inside the code modules to be efficient enough

I know some ASM-fu that might help with that

Haha, you just want to see the source
Well there's nothing magical about it. It's just a 2048 tap Fir filter with an IR as it's coefficient. The structure of the FIR is pretty close to the one on the "visual designer" by rl. I really liked the way an array was be inputted to the code in that schematic. Even tho it has it's drawbacks.

What kind of ASM-fu's you might have to get arrays inside the code faster?

[bootsy]

why don't you just give up on the zero latency approach?

[matti]

why don't you just give up on the zero latency approach?

Any ideas how to do that? I thought of doing a simple FFT with code, but it seems like it would be a bit too much work.

Btw. i found a better way of getting the data inside the code. That way i got the cpu usage slimmed down to half(or less) and now it works with stereo impulses. -> v2
There's also a mono version with lower cpu usage. Stereo version has a 1 sample latency, mono 4 sample.