Battery usage when asleep

Question

MIDI Target Manufacturer(s): Original, Generic

I've noticed that if I leave MD running when the iPad is asleep, battery consumption is much higher than it is without MD running. Is this to be expected? I would have thought that when the iPad is asleep, the app should basically do absolutely nothing. Does it keep checking for MIDI interfaces or something like that?

I'm running MD version 2.98.1, IOS 12.1.

Answer 1

Thanks for the question. MD follows all the typical rules of good-citizen iOS apps. If it gets moved to the background, it will spin down the frequency of all “polling” operations, including the search for Bonjour connections and the actual incoming MIDI queue. In addition, UI updates should not occur when the screen is off or the App is in the background.

MD could probably be much more battery efficient while it’s on the screen and while it’s off. I’m not aware of how it handles the iPad-off (asleep) state, but judging from your question, the answer is that it’s not great.

One thing to try is to background MD before suspending the iPad.

For now, I think we can consider this a deficiency, and we’ll move to put in the hours to improve battery performance at some point.

Thanks for reporting.

Comments

Thanks. I think I had backgrounded MD when I checked this, but I'll do it again and report back.

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I finally got round to doing this test and I've confirmed that with MD backgrounded and the iPad asleep, the battery consumption is way higher than if MD is not running at all. With MD backgrounded, the battery dropped from 100% to about 60% in a few days (the iPad was asleep for the whole time). Without MD running at all over a similar period, it only lost a few percent.

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How is MD connected and to what? What other apps were running? We do still poll for midi even in the background, but that use could be halved or quartered, possibly doing the same (or less? Or more?) to/for battery life.

Thanks!

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No other apps were running and MD was not connected to anything. When I use it, it's connected to a Bluetooth MIDI device, but that was not even powered up when I tested the battery drain. Hope that's the info you wanted. Do ask, if not. Thanks.

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Yeah, that's helpful. Makes sense given how the code is written, too. We could optimize for this, but it's not a high priority yet. Thanks for the investigation... frankly I'm thinking it's "not too bad" but I see the other POV, too.

Answer 2

Thanks for the question. MD follows all the typical rules of good-citizen iOS apps. If it gets moved to the background, it will spin down the frequency of all “polling” operations, including the search for Bonjour connections and the actual incoming MIDI queue. In addition, UI updates should not occur when the screen is off or the App is in the background.

MD could probably be much more battery efficient while it’s on the screen and while it’s off. I’m not aware of how it handles the iPad-off (asleep) state, but judging from your question, the answer is that it’s not great.

One thing to try is to background MD before suspending the iPad.

For now, I think we can consider this a deficiency, and we’ll move to put in the hours to improve battery performance at some point.

Thanks for reporting.