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Re: Coreaudio-api Digest, Vol 11, Issue 139

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Re: Coreaudio-api Digest, Vol 11, Issue 139

Subject: Re: Coreaudio-api Digest, Vol 11, Issue 139
From: Clement Prem <email@hidden>
Date: Tue, 19 Aug 2014 16:30:59 +0530

Audio stops playing on sleep button call issue

I found the solution at

https://developer.apple.com/library/ios/qa/qa1606/_index.html

The issue is related to sample rate changing in sleep mode to reduce power consumption (not sure :().

You need to set kAudioUnitProperty_MaximumFramesPerSlice to 4096 in all you nodes.

UInt32 maxFPS = 4096;

AudioUnitSetProperty(player->filePlayerUnit, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Global, 0, &maxFPS, sizeof(maxFPS));

AudioUnitSetProperty(player->mxUnit, kAudioUnitProperty_MaximumFramesPerSlice, kAudioUnitScope_Global, 0, &maxFPS, sizeof(maxFPS));

AUGraphInitialize(player->graph);

Clement

On Mon, Aug 18, 2014 at 12:30 AM, <email@hidden> wrote:

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Today's Topics:

1. Re: Advice with timing & Audio Units (iOS) (IDAS)
2. Audio stops playing on sleep button call (Clement Prem)

----------------------------------------------------------------------

Message: 1
Date: Sun, 17 Aug 2014 00:37:43 +0100
From: IDAS <email@hidden>
To: email@hidden
Subject: Re: Advice with timing & Audio Units (iOS)
Message-ID: <email@hidden">email@hidden>
Content-Type: text/plain; charset=windows-1252

Thanks Kevin, this is helpful.

So this implies that that the master clock is always handled internally by Core Audio?

On 13 Aug 2014, at 20:41, Kevin Dixon <email@hidden> wrote:

> It seems you may be more interested in the property
> kAudioUnitProperty_Latency. As far as I know, time stamps should be
> consistent across channels, etc, as the entire Audio Unit Graph should
> be representing the same point in time.
>
> Given the Latency property, you should be able to compensate by
> delaying other instruments to match the greatest reported latency.
>
> -Kevin
>
> On Wed, Aug 13, 2014 at 12:23 PM, IDAS <email@hidden> wrote:
>> I’ve recently tackled Audio Unit programming and absorbed the documentation
>> on Apples website. Whilst I feel I have a good grasp of everything
>> conceptually, I wanted to check my approach to writing a sequencing app on
>> iOS.
>>
>> So my question is around the timing required to drive the sequencer. When
>> recording or playing back audio (& MIDI), I want to understand the process
>> of synchronising the render callbacks in the Audio Units to my master clock
>> on the device.
>>
>>
>> Audio Units have their own AudioTimeStamp and I wanted to understand more
>> about how this is sourced and how it can also be manipulated to hide
>> latency.
>>
>>
>> Programatically, am I thinking about this correctly?
>>
>>
>> Thanks.
>>
>>
>> _______________________________________________
>> Do not post admin requests to the list. They will be ignored.
>> Coreaudio-api mailing list (email@hidden)
>> Help/Unsubscribe/Update your Subscription:
>>
>> This email sent to email@hidden

------------------------------

Message: 2
Date: Sun, 17 Aug 2014 20:12:34 +0530
From: Clement Prem <email@hidden>
To: email@hidden
Subject: Audio stops playing on sleep button call
Message-ID:
<CAE+HNvth_9raS_hirBo-j8Tz8JWjdqWN6TRSY=email@hidden>
Content-Type: text/plain; charset="utf-8"

Hi
I am implementing an audio player using AUGraph/ audio units. It works
perfectly when the app is in foreground or background. But if I press sleep
button it stops playing immediately.
How can I fix this issue?

P.S. Background mode for audio is enabled.
Regards
Clement Prem R
Software Engineer / Project Lead -iOS
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