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AUM / Model D crackling and DSP spikes

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Comments

  • OscarSouthOscarSouth

    I’m having performance issues with AU gui too. Haven’t had any problems with reliability in performance though as I just controlled it with an external controllers. Also found the IAA interface to be fine.

  • RUST( i )KRUST( i )K

    Thank God for Animoog, DRC, and Volt.

  • j_liljedahlj_liljedahl

    I have searched a lot and can't find anything in AUM's code that could give rise to this behaviour (UI activity affects DSP performance). I've even been in direct contact with a CoreAudio software engineer at Apple. As far as I know, this is a bug in iOS itself (regarding thread priority or CPU throttling) and not related to AUM. I assume you see similar problems in other hosts?

  • j_liljedahlj_liljedahl

    UPDATE: it seems this actually is an issue about CPU throttling by iOS itself. The reason this happens less in other hosts could be that AUM uses too little CPU by itself :) In some cases, it might help to give the CPU some "burn in" by doing heavy tasks, forcing the CPU speed up.

    Also, a kind of crazy theory of why a reboot might help is that not only does it "clean away" stray processes etc, but it also keeps the CPU warm and fast because of all the housekeeping tasks that iOS does right after a reboot!

  • AndyPlanktonAndyPlankton

    @j_liljedahl said:
    UPDATE: it seems this actually is an issue about CPU throttling by iOS itself. The reason this happens less in other hosts could be that AUM uses too little CPU by itself :) In some cases, it might help to give the CPU some "burn in" by doing heavy tasks, forcing the CPU speed up.

    Also, a kind of crazy theory of why a reboot might help is that not only does it "clean away" stray processes etc, but it also keeps the CPU warm and fast because of all the housekeeping tasks that iOS does right after a reboot!

    Black magic going on right there !

    Incredibly useful info..thanks :)

  • CracklePotCracklePot

    Sounds like me getting up in the morning. Principles of Motion in effect.

  • thenonanonymousthenonanonymous

    @j_liljedahl said:
    UPDATE: it seems this actually is an issue about CPU throttling by iOS itself. The reason this happens less in other hosts could be that AUM uses too little CPU by itself :) In some cases, it might help to give the CPU some "burn in" by doing heavy tasks, forcing the CPU speed up.

    So is this a good argument that the standard in iOS audio should move to higher sample rates, lower frame rates? Would this be enough?

    Or pretty soon we might see "Overdrive" switches in host apps?

  • j_liljedahlj_liljedahl

    @thenonanonymous said:

    @j_liljedahl said:
    UPDATE: it seems this actually is an issue about CPU throttling by iOS itself. The reason this happens less in other hosts could be that AUM uses too little CPU by itself :) In some cases, it might help to give the CPU some "burn in" by doing heavy tasks, forcing the CPU speed up.

    So is this a good argument that the standard in iOS audio should move to higher sample rates, lower frame rates? Would this be enough?

    I don't know. Someone that experiences the cracklings should try it! But I think it's mostly an argument that Apple should fix those issues!

    Or pretty soon we might see "Overdrive" switches in host apps?

    I might actually try that, and add a hidden "burn some CPU" button in AUM :)

  • Artefact2001Artefact2001

    @thenonanonymous said:

    @j_liljedahl said:
    UPDATE: it seems this actually is an issue about CPU throttling by iOS itself. The reason this happens less in other hosts could be that AUM uses too little CPU by itself :) In some cases, it might help to give the CPU some "burn in" by doing heavy tasks, forcing the CPU speed up.

    So is this a good argument that the standard in iOS audio should move to higher sample rates, lower frame rates? Would this be enough?

    Could you let me know how i’d do this in relation to AUM? When I try and change the sample rate it tells me the hardware doesn’t support it, or it’s being controlled by another app (nothing else running). What about frame rate, can I change this? thanks!

  • midiSequencermidiSequencer

    @j_liljedahl said:
    UPDATE: it seems this actually is an issue about CPU throttling by iOS itself. The reason this happens less in other hosts could be that AUM uses too little CPU by itself :) In some cases, it might help to give the CPU some "burn in" by doing heavy tasks, forcing the CPU speed up.

    Also, a kind of crazy theory of why a reboot might help is that not only does it "clean away" stray processes etc, but it also keeps the CPU warm and fast because of all the housekeeping tasks that iOS does right after a reboot!

    I've done some study of thread behaviour in switching apps in AUM (specifically measuring Quantum thread running the loop) and I've noticed that, like Jonatan says, IOS seems to throttle CPU - this results in any thread using precise timing to glitch. What I'm seeing is a dip in CPU usage on that thread and there's nothing I can do about it (yet - still investigating). Like Jonatan says we tune our apps to be low CPU but it now seems that threads are getting punished to make way for apps that are heavy on the GPU (e.g. Moog apps that use the metal shader) especially when they transition between foreground & background.

    I've been using the trick 'keeping the thread busy' for awhile - thats why Quantum has audio - but IOS CPU throttling we have no control over.

  • thenonanonymousthenonanonymous

    @Artefact2001 said:
    Could you let me know how i’d do this in relation to AUM? When I try and change the sample rate it tells me the hardware doesn’t support it, or it’s being controlled by another app (nothing else running). What about frame rate, can I change this? thanks!

    Which audio interface are you using? Your hardware needs to support the sample rate you are changing too... for example, if you're only using a new iPhone by itself, and not using headphones plugged in, the only sample rate supported is 48kHz (certain headphones might change this?). You change the frames via the "Buffer Size" setting in AUM settings.

  • johnfromberkeleyjohnfromberkeley

    Here's an interesting thread on restricting the ProMotion refresh rate in the new Pros. @ImortalTrashcan reports that it seems to help.

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