Apple

On 8 Aug 2012, at 12:33, Michael Tyson <email@hidden> wrote:

Good lord. Ignore all of that!

I'm utterly mystified as to what was happening before - chances are it's my own stupid mistake/bad assumption somewhere along the line - but I've discovered that PlayAndRecord really does appear to be able to be used across multiple apps, as long as they're all overriding the 'kAudioSessionProperty_OverrideCategoryMixWithOthers' property properly.

This is what I'd expected from the beginning, but something must've gone awry in my prior experiments, which after reboot is now actually behaving as expected.

How embarrassment - so the upshot is all this is a total nonissue. The odd one-at-a-time problems we were seeing must've been due to something totally different - some odd audio session state problem.

On 8 Aug 2012, at 11:28, Michael Tyson <email@hidden> wrote:

Hi guys,

I want to get your opinion on something we've just discovered.

In short: We can use the MediaPlayback audio session category in a recording app, and it means that more than one app can use the mic at a time, which is great news for multitasking music apps. I want to know if anyone can think of reasons this shouldn't be used all the time, in music apps.

Apple's documentation and sample code all indicate that developers need to use the PlayAndRecord/Record audio session categories if their app records audio. I for one have always done this, without thinking, taking Apple's word for it. But only one app at a time can use said categories - any other app currently using it will have its audio session interrupted, and will be suspended.

This is a poor state of affairs for music apps, which users often want to use in tandem. It's also particularly poor for Audiobus - if you want to use a looper and a guitar amp app at the same time, and they both use PlayAndRecord, then there needs to be a way to allocate that resource between the apps: Extremely messy, as I've discovered during the last few days while implementing that very thing into Audiobus.

We discovered yesterday that all this is wrong: You can actually use the MediaPlayback category perfectly well with an app that records from the microphone. This may be obvious to some, but we had no idea you could do it, and it changes a lot, for music apps: It means they'll all work together perfectly.

The only hitch when using MediaPlayback is that you can't query the kAudioSessionProperty_CurrentHardwareInputNumberChannels session property, but as I mentioned in another thread, this isn't a problem - you just switch into PlayAndRecord to query the property, and switch back, and you only need to do so if no other app is using PlayAndRecord - otherwise, you can query the property regardless of the session category.

So, my question is this:

Can anyone think of a reason MediaPlayback shouldn't be the standard category used in music apps, whether they record audio or not?

We would like to mandate its use for Audiobus-compatible apps, as it will mean all participating apps will work perfectly together with no resource contention. I just want to make sure there's no obvious arguments against it.

Cheers for your time!
Michael
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