Captain's Log: Stardate 79000.1

Whoa, it's been way too long since I updated the devlog. Here goes!

2025 MIDI Innovation Awards

Really quickly: Anukari is an entry in the 2025 MIDI Innovation Awards, and I would really appreciate your vote. You can vote on this page by entering your email and then navigating to the Software Prototypes/Non-Commercial Products category and scrolling way down to find Anukari. You have to pick 3 products to vote in that category. (I wish I could link to the vote page directly, but alas, it's not built that way.)

The prize for winning would be a shared booth for Anukari at the NAMM trade show, which would be a big deal for getting the word out.

Multichannel I/O Support

A while back, Joe Williams from CoSTAR LiveLab reached out to me asking if Anukari had multichannel output support. Evidently the UK government is investing in the arts, which as an American is a pretty (literally) foreign concept. One of the labs working on promoting live performance is LiveLab, and they have a big 28-channel Ambisonic dome. Joe saw Anukari and thought it would be cool to create an instrument with 28 mics outputting to those 28 speaker channels.

I'd received several requests for multichannel I/O, but hadn't yet prioritized the work. The LiveLab use case is really cool, though, and Anukari will be featured in a public exhibit later this month, so I decided to prioritize the multichannel work.

Anukari now supports 50x50 input/output channels. In the standalone app, this is really simple, you just enable however many channels your interface supports and then inside Anukari you assign each audio input exciter or mic to the channels you want.

It also works for the plugin, but how you utilize multichannel I/O is very DAW-dependent. Testing the new feature was kind of a pain in the butt, because I have about 15 DAWs for testing, and multichannel is a bit of an advanced feature, so I ended up watching a zillion tutorial videos. Every DAW approaches it a bit differently, and the UX is generally somewhat buried since it's a nice feature. But it works everywhere, and it is extremely cool to be able to map a bunch of mics to their own DAW tracks and give them independent effects chains and so on.

Behind the scenes, it was really important to me that the multichannel support did not impact performance, especially when it was not in use. I'm very happy to say I achieved this goal. When you're not using multichannel I/O, there is zero performance impact. And even in 50x50 mode the impact is very low. Anukari is well-suited for multichannel I/O since each mic is tapping into the same physics simulation at different points/angles, so none of the physics computations have to be repeated/duplicated. Really the only overhead is copying additional buffers into and out of the GPU. On the Windows CUDA backend, that's a single DMA memcpy, which is very fast. And on the macOS Metal backend, it's unified memory, so no overhead at all. All that remains is the CPU-CPU copy into the DAW audio buffers, which is very, very fast.

I look forward to posting about the LiveLab exhibit once it happens.

ASIO Support

It's a pretty big oversight that the Windows version of the Anukari Beta launched without ASIO support. I'm not quite sure how I missed this important feature, but I've added it now.

I think I always assumed it was there, but when using JUCE the ASIO support is not enabled by default because you need to get a countersigned agreement from Steinberg to use their headers to integrate with ASIO. I already had a signed agreement with them for the VST3 support, but ASIO is a completely separate legal agreement and so I went through the steps to get that as well.

ASIO support makes the standalone app perform much better (in terms of latency) for people with ASIO compatible sound interfaces.

AMD Radeon Crashes

Officially speaking, Anukari explicitly does not support AMD Radeon hardware. This is a bit of a long story, which at some point I will write about in more detail. But the short version is that the Radeon drivers are incredibly inconsistent across the Radeon hardware lineup, which makes it extremely difficult to offer full support. For some Radeon users, Anukari works perfectly, and for others it is unstable, glitchy, or crashes, in many different unique ways.

The story I'll write about for this devlog entry, though, is the extremely frustrating case that I solved for users that have both an AMD Radeon and an NVIDIA graphics card in the same machine. This is actually a common situation, because many (most? all?) AMD Ryzen CPUs include integrated Radeon graphics on the CPU die. So for example there are a lot of laptops that come with an NVIDIA graphics card, but also have a sort of "vestigial" Radeon in the CPU that is normally not used for anything.

In the past, Anukari just worked for users with this configuration, since when it detects multiple possible GPUs to use for the simulation, it would automatically select the CUDA one as the default. However in the 0.9.6 release, Anukari began crashing instantly at startup for these users.

This was pretty confusing, because I have comprehensive fuzz and golden tests that exercise all the physics backends (CUDA, OpenCL, Metal). These tests abuse the simulation to an extreme extent, and I run them under various debugging/lint tools to make sure that there are no GPU memory errors, etc. And across my NVIDIA, macOS, and Intel Iris chips, they all work perfectly.

Luckily I had a user who was extremely generous with their time to help me debug the issue. I sent them instrumented Anukari binaries, and eventually was able to pinpoint that it was crashing inside the clBuildProgram() call.

Now, you might think that what I mean is that clBuildProgram() was returning an error code, and I was somehow not handling it. No, Anukari is extremely robust about error checking. I mean it was crashing inside the kernel and clBuildProgram() was not returning at all due to the process aborting. This is with perfectly valid arguments to the function. So, obviously, this is a horrible bug in the AMD drivers. Even if the textual content of the kernel has e.g. a syntax error, clearly clBuildProgram() should return an error code rather than crash.

The really fun part is that I've only seen this crash on the hardware identifying as gfx90c. On other Radeons, this does not happen (though some of them fail in other ways). This is what I mean about the AMD drivers being extremely inconsistent.

Now, as to why this crash happened at startup, it's because during device discovery Anukari was compiling the physics kernel, and any device where compilation failed would be assumed incompatible and omitted from the list of possible backends. I added this feature after encountering other broken OpenCL implementations like the Microsoft OpenCL™, OpenGL®, and Vulkan® Compatibility Pack which is an absolute disaster.

So the workaround for now is that Anukari no longer does a test compilation to detect bad backends. This resolves the issue, although if the user manually chooses the Radeon backend on gfx90c it will unrecoverably crash Anukari.

Longer-term, given the Radeon driver bugs, I doubt I'll ever be able to fully support gfx90c, but I ordered a cheap used laptop off eBay with that chip in it so that I can at least narrow down what OpenCL code is causing the driver to crash. I know that it's something the driver doesn't like about the OpenCL code because it did not always crash, and the only difference in the meantime has been some improvements to that code. Hopefully I can find a workaround to avoid the driver bug, but if not I might add a rule in Anukari to ignore all gfx90c chips.

(Side-note: actually the first used laptop with a gfx90c chip that I bought off eBay was bluescreening at boot, so I had to buy a second one. These inexpensive Radeon laptops are really bad.)

Not all hope is lost for Radeon support. I recently upgraded my main development machine, and the Ryzen CPU I bought has an on-die Radeon, and it works flawlessly with Anukari. So maybe what I will be able to do one day is create an allow-list for Radeon devices that work correctly without driver issues. Sigh. It is so much easier with NVIDIA and Apple.

Parameter Randomization

Unlike the features above, this one hasn't been released yet, but I recently completed work to allow parameters to be randomized.

For Anukari this turned out to be a bit of a design challenge, since the sliders that are used to edit parameters are a bit complex already. The tricky bit is that if the user has a bunch of entities selected, the slider edits them all. And if the parameter values for each entity vary, the slider turns into a "range editor" which can stretch/squeeze/slide the range of values.

So the randomize button needs to handle both the "every selected object has the same parameter value" and "the parameter varies" scenarios. For the first scenario with a singleton value, it's simple: pressing the button just picks a random value across the full range of the parameter and assigns it to all the objects.

But for the "range editor" scenario, what you really want is for the randomize button to pick different random values for each entity, within the range that you have chosen. There's one tricky issue here, which is that it is very normal for the user to want to mash the randomize button repeatedly until they get a result they like. This will result in the range of values shrinking each time (since it's very unlikely that the new random values will have the same range as before, and the range can only be smaller)!

So the slider needs to remember the original range when the user started mashing the randomize button, and to reuse that original range for each randomization. This allows button mashing without having the range shrink to nothing. It's important, though, that this remembered range is forgotten when the user adjusts the slider manually, so that they can choose a new range to randomize within.

Another kind of weird case is when the slider is currently in singleton mode, meaning that all the entities have the same parameter value, and the user wants to spread them out randomly over a range. This could be done by deselecting the group of entities, selecting just one of them, changing its value, then reselecting the whole group, which would put the slider into range mode. But that's awfully annoying.

I ended up adding a feature where you can now right click on a singleton slider, and it will automatically be split into a range slider. The lower/upper values for the range will be just slightly below/above the singleton value, and the values will be randomly distributed inside that range. So now you can just right click to split, adjust the range, and mash the randomize button.