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A low latency guitar effects processor suitable for running on a Raspberry Pi

github.com

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Re: A low latency guitar effects processor suitable for running on a Raspberry Pi

#81

Post by pengaru »

I've found the RPi4B to be somewhat awful for low-latency audio usage.

My particular use case is simply playing MP3s read from mmc through an MBox1 on USB.

No matter how much irqbalance, isolcpus, taskset magic, it never gets absolutely perfect. It gets better, but there's always spurious delays exhibited as occasional pops and clicks in the audio output.

I'm hopeful that [0] will improve the situation, but haven't had time to really dig into it let alone build a custom bleeding-edge mainline kernel - which I'm not even sure supports all the Pi4B hardware.

It's asinine that an otherwise idle 4Cx1.8Ghz machine can't even play MP3s on a USB MBox1 flawlessly with zero special effort...

[0] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/lin...

Re: A low latency guitar effects processor suitable for running on a Raspberry Pi

#85

Post by jzombie »

honkycat wrote: post #43

I've had some amazing ( horrible ) adventures in low latency music stuff lately. It has made me think about going back to the hardware side of music production. Previously I was an ableton-only dude. All of the vst plugins are CPU bound and even though i have a top of the line i7 and 32 gigs of ram, my computer slows to a crawl when editing even moderate sized songs. Specifically, there is an nvidia bug that introduc…

I don't know how this compares to your i7, but I dabble around using Pro Tools w/ about 15 or 20 tracks at a time with several effects running in unison, on an M1 Pro processor w/ only 16 gigs RAM, and I typically stay under 20% usage according to Activity Monitor.

I mostly play guitar and don't notice the latency in most effect chains that I use.

Re: A low latency guitar effects processor suitable for running on a Raspberry Pi

#87

Post by honkycat »

jzombie wrote: post #85
honkycat wrote: post #43

I've had some amazing ( horrible ) adventures in low latency music stuff lately. It has made me think about going back to the hardware side of music production. Previously I was an ableton-only dude. All of the vst plugins are CPU bound and even though i have a top of the line i7 and 32 gigs of ram, my computer slows to a crawl when editing even moderate sized songs. Specifically, there is an nvidia bug that introduc…

I don't know how this compares to your i7, but I dabble around using Pro Tools w/ about 15 or 20 tracks at a time with several effects running in unison, on an M1 Pro processor w/ only 16 gigs RAM, and I typically stay under 20% usage according to Activity Monitor. I mostly play guitar and don't notice the latency in most effect chains that I use.

Yeah it should perform way better than it does currently. There is a driver bug for Nvidia cards that causes it to run slowly and poorly.

It is extremely frustrating.

Re: A low latency guitar effects processor suitable for running on a Raspberry Pi

#88

Post by H1Supreme »

woudsma wrote: post #7

Very cool, I've ordered a Raspberry Pi touchscreen this weekend and it should arrive today. I want to make a MIDI sequencer with it, or at least play with the idea. I hope my old Raspberry Pi can work with MIDI (over USB) without too much latency..

Depends on how you want to utilize it. If you want to connect it to a computer as a MIDI device, you'll have to use an Rpi4 or one of the Pi Zero's. The Pi's The RtMidi library is probably your best bet for getting started. I found the ALSA library to suit my workflow a bit better, but the setup is pretty obtuse. RtMidi is much more user friendly in that regard.

Also, look into implementing the Ableton Link library. It runs over your network, and is honestly astounding how well it sync's devices.

Re: A low latency guitar effects processor suitable for running on a Raspberry Pi

#89

Post by tastysandwich »

hendry wrote: post #86

Surprised that a (local) Web call can be considered low latency. Isn’t this why people use grpc etc?

I'm assuming that the Web UI is just for changing settings.

The low latency would refer to the latency of the audio input (guitar) being processed and producing a sound. Ideally you want no discernible delay between when you hit a string and when a sound is produced.

As for how much delay is considered "acceptable", I'm not going to open that can of worms...

Re: A low latency guitar effects processor suitable for running on a Raspberry Pi

#90

Post by tastysandwich »

> The root of it is the Transform function which takes an input signal, performs any kind of transformation, and returns an output. All input and output values should remain in the range [-1, 1] otherwise you'll produce some really gnarly popping and cracking.

So you have to make all your own effects in code? It would be cool if it connected to something like Guitarix (open source) so you could use existing guitar effects. (Disclaimer: I've never used Guitarix, so it might sound shit)

Btw, for anyone who doesn't play guitar, but is interested... Gone are the days of those huge pedal boards and having to buy 30 different pedals. Emulation is getting really really good. You can either buy a multi-effects pedal and use that onstage. Or if you're in the studio, NeuralDSP is software which can emulate basically any sound you're after. It's expensive though, but it sounds better than free alternatives like Amplitube.

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