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Measuring processing power usage of AU Effects: Why don't we establish a 'standard'?
The way they run inside a host should theoretically make them very easy to create a system for measuring 'proportionate' processing power usage. For example running a single channel in AUM with same settings, playing the same audio from it's file player through each AU and recording processor usage. This way, we'll at least get a good idea of how their power usage in comparison with each other. A pretty useful reference to have!
I'm sure between all of us we've got every possible AU on every possible device. If we can get three similar readings from each AU on 3 different devices of the same model then I think we can say that this reading is reasonably reliable.
Who's up for it?
Oscar
Comments
Excellent idea. I had been considering Cubasis for this since a project file can be encapsulated with MIDI data feeding AU, and easily shared
I'd say that AUM is essential as it's probably the most comment host, and if we can get enough people with Cubasis on their devices then we can test with that too (I don't have it myself). Will be informative to have from two significant hosts.
Currently there are limits as to how much processing power an AU can use as determined by the iOS AU specifications. The problem with coming up with a universal measuring process for an AU is that how much processing is required by a particular AU synth instance, for example, can be very dependent upon the particular patch being run in the AU as well as the polyphony. There may also be other factors which I am not aware of which could effect how much processing an AU instance may require. Which iOS device, iOS updates, AU and AU app host updates, latency settings, and concurrently running apps may also effect the results.
Such an effort may benefit from the input of a developer who could suggest factors and conditions that would be important to take into account when coming up with an AU measurement system.
That's the challenge for us!
We're not measuring accurately in a scientific way. Just determining in a practical way how different AU's compare to each other. The zMorz EQ thread gave me the idea; it'd be useful to simply know out of the available EQs, which is most power hungry, which least etc. Allows for a more carefully considered decision.
Accurate values wouldn't be necessary, just a general awareness. I'm sure between all the insight here, we could come up with a process to determine this with some degree of certainty.
I'd prefer a scientific approach as they document what they've done, the conditions used, and present objective measurable results.
I think apps such as an EQ which don't vary as much in their resource usage would benefit the most from such a system of measurement. Coming up with some standard conditions for various classes of apps in spreadsheet format may be useful. Perhaps even points of failure where you have a set up with a given latency where you keep adding instances of an AU app until you start hearing audio glitches may be one approach. Coming up with comparable presets for different apps would be a critical aspect. For EQ or other effect apps, having a standard audio file that's processed where people can compare the dry signal with the wet signal from comparable AU apps would also be useful since quality and not just quantity is significant.
I'd also be interested to see precise measurements, but I can't think of any viable way to do it when considering such diverse AU's with such widely variable use cases. For my own (and I assume most people who are primarily just using these things 'practically' for music making) I think that a general and proportionate grading will be sufficiently useful for compositional decision making. I imagine that most people like myself don't/wouldn't calculate exact processor capacity but just have a good general 'feel' and intuition for what their device can handle (and imagine working out precise values for every type of device).
If you have a plan for making it possible to measure more accurately though then it would definitely be interesting to hear, even in theory if not in practise.
Presumably an AU standard for processing usage would be information used by musicians to evaluate the usefulness of an app in their music workflow. Not all musicians have the same workflow, for instance, the latency requirements for live playing may be quite different than for a DAW based sequencing approach.
A scientific approach isn't limited to precise quantitative measurements, qualitative measurements are also routinely used in scientific research.
Coming up with relevant conditions for AU testing for musicians would seem to be the first step as you will need musicians willing to perform the tests and musicians who find the results relevant to their app purchasing decisions.
GIGO stands for Garbage In Garbage Out meaning that determining the relevant factors to test and how to appropriately test them will determine the relevancy of the information provided to forum members.
Some observation of specific AU setups could help determine which sorts of apps are easier to test and would be the first place to start. Does the processing power for EQ AU apps change based upon the AU app settings? If not, then you could do tests using a couple of different latency settings. One such test would be the number of concurrent AU instances to reach audio glitching in a particular setup or the number of instances to reach a particular CPU usage reading in an AU host app.
If the processing power of an AU app does change depending upon the presets you use, you could determine low, medium, and high processing usage presets and then perform the same type of tests as for apps which don't change except repeat the test for low, medium, and high usage cases.
All of this assumes the testers have started their devices from a clean state and there aren't any other apps running other than the AU app and the AU host so you don't get inconsistent results due to IAA zombies for example. The device, iOS, and app version numbers, and presets used would all be reported along with the test results. For apps without standard presets, the tester could create a preset and take a screenshot of it so that the preset can be replicated by other users on different devices to complete the testing.
For synths you could run tests based upon patch complexity, polyphony, and tempo. Standard Fugue Machine settings could be used as part of this testing process.
All of this testing would rely upon people willing to perform the tests and some types of apps would be more straight forward to test than others. The more variability in processing usage based upon AU app settings, the more testing would be required to provide a more accurate assessment of the AU app's processing usage.
Alternatively, there are several iOS music websites that might be approached about standard AU app testing and if there's sufficient interest Patreon might be a way to support their efforts in this regard.
Thanks for an in depth reply!
I have to shoot out now and will be busy this evening but I will read it carefully when I get the chance to sit down with it.
We're all gonna die someday.
I actually misread this post, I was more interested in a standard test suite that would measure the performance of different iPad models
General (not specific to audio performance) iOS benchmarks:
https://browser.primatelabs.com/ios-benchmarks
Yes aware of these, I just recall quite some time ago on the Cakewalk forums we had a standard project that would test real world performance of different CPU/RAM/motherboard configurations - particularly when AMD Athlon vs Intel Pentium was a thing, it really helped clarify the impact of hardware decisions for DAW use.
For example it's not yet quantitively clear what audio impact the RAM configuration makes between the 12.9 and 9.7 iPad Pro models
Thanks for the replies everyone. I agree, it's an interesting topic.
Regarding the threads agenda, it seems that everyone either thinks I'm talking about measuring the power of different Apple products or is not satisfied at anything less than 'proper scientific method' to 0.001% accuracy. I don't think in 'real life' terms that this is going to happen (I know that I'm busy enough and I'm sure that everyone else is too). Sometimes I forget that I'm posting on a computer forum
I'm happy to share any useful info that I discover from any practical testing that I do with my two devices however. Will keep you updated. I've not got all the different AU's on offer but it could be helpful to keep building on the collective body of knowledge here.
If this is something you believe I've advocated for, then I haven't been sufficiently clear.
Nah it seems more of the general consensus of the board. It's also something that I'm interested in but just not something that I want to commit to spearheading right now (I'm in the middle of a big house move to a different country whilst also rushing to finish my Master Thesis before said date!)
@OscarSouth good luck with finishing up your thesis and the move.
Only a few people have commented on the thread so perhaps this is an indication that people aren't really interested in creating a standard for testing AUs? I have my own personal issues to address at this time but when they've been resolved in the next month or so, I'll setup and share my own testing procedure unless other forum members come up with something before then.
Yeah agreed. Better to take the path of least resistance, and I'm also happy to share any useful info that I find personally. I'd definitely up for any collaboration in this area.