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Bugs Database

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This page details the current known issues that affect musicians in iOS, Audiobus or other significant third-party products. Subscribe above to receive notifications when we update this database.

Bug ID Product Description Workaround Status

iOS 10

Core Audio

Inter-App Audio node input callback run twice per render session, on 2 different threads, when hosted

If an Inter-App Audio node configures its Remote IO audio unit with an input callback (kAudioOutputUnitProperty_SetInputCallback) and also publishes it (AudioOutputUnitPublish), then when it is hosted within Inter-App Audio, the input callback is called twice for each time interval, once from a thread called AURemoteIO::IOThread, once from a thread called

This is a problem for many apps that both publish their audio units via IAA and take input from the microphone, as this can cause double processing of the input handling code.

The only workaround I have found is to defer input handling to the audio unit's render callback instead, and only use the input callback to retrieve the AudioTimeStamp. If one uses the mSampleTime element of the AudioTimeStamp, however, this is still likely to lead to problems as the sample times for the two invocations are different: upon hosting, the thread reports sample times starting from zero.

Pending. Reported to Apple on June 29 2017 (Radar 33049097).


iOS 8

Core Audio

iPad Air 2

High playthrough latency on iPad Air 2

On the iPad Air 2, playthrough latency (input to output delay) is very high; approx. 90 milliseconds.

This has been demonstrated when using any headphones with the device, except for Apple's headphones with built-in mic, or when using the device's built-in speaker output.

The issue can sometimes, but not always, be resolved by enabling Measurement Mode.

Use Apple's headphones with built-in mic.

Pending. Reported to Apple on Nov 25 2014 (Radar 19076611).


iOS 8

Core Audio

IAA buzz when launching some apps

With an Audiobus or Inter-App Audio session active, launching any app that does any of the following causes the AB/IAA session to freeze:

  1. enables Measurement Mode after setting the audio session active,
  2. initializes audio units prior to setting the audio session category with MixWithOthers,
  3. assigns the audio session category both before and after setting the audio session active, with the AllowBluetooth option provided for one or both category assignments.

This causes a sawtooth-like tone that persists when some apps are launched, until either the launched app is closed again, or the input app is brought to the foreground.

Note: This bug was originally described as being caused by Measurement Mode, but further investigation has revealed this only occurs when assigning AVAudioSessionModeMeasurement after setting the audio session active, and has revealed additional causes.

Disable measurement mode/Bluetooth audio in affected apps, if possible, or switch to the input app when this happens.

Pending. Reported to Apple on Oct 28 2014 (Radar 18793520).


iOS 8

Core Audio

Measurement Mode doesn't work

Measurement Mode (the Audio Session mode that improves bass response with certain input devices) does not function at all on iOS 8: turning on "Measurement Mode" in Audiobus has no effect.


Pending. Reported to Apple on Oct 1 2014 (Radar 18510446).


iOS 7/8


Error in peer discovery: no addresses resolved

Sometimes newly-discovered peers are not resolved correctly, resulting in no usable addresses for communication.

In Audiobus, this is seen as apps that do not respond to Audiobus, either not switching back upon launch, or not showing the connection panel, and not processing audio correctly.

Close and restart problematic app, or reboot device if that fails.

Pending. Reported to Apple on Oct 27 2014 (Radar 18778381).


iOS 8


Inconsistent behaviour with Bonjour system

Assorted inconsistent behaviour with peer resolution, including resolution failures with -72007 timeout errors, and failure to clean up old registrations from no-longer-running apps.

This generally stops apps connecting to Audiobus (no switch back on launch, no connection panel, no audio).

Close and relaunch all apps, or reboot device.

Pending. Reported to Apple on Sep 25 2014 (Radar 18452252).

IAA Error bug

iOS 7/8

Inter-App Audio

Assorted Inter-App Audio hosting errors

Sometimes, Inter-App Audio hosting fails. This issue causes an "Error" label to appear on sender or filter apps, and no sound.

Close and relaunch all apps, or reboot device.

Still gathering info. We don't yet know why this is happening.
Sometimes this is due to developers' mistakes, but sometimes it occurs without apparent cause. Restarting apps or rebooting generally solves the problem.

Effect app input/output slot bug


On iOS 7, older effect apps show up in input and output slot

On iOS 7, effect apps build against earlier versions of the Audiobus SDK than 2.1 appear in the "input" and "output" selector lists, incorrectly, and these entries do nothing when tapped.


Fixed in Audiobus 2.1.8 (13 Nov 2014).


iOS 8


Screen jail for secondary windows not rotated correctly

In apps built with the iOS 8 SDK that are being scaled to fit the screen (mainly, non-iPhone 6 native apps running on an iPhone 6), secondary windows such as the Audiobus connection panel are not positioned correctly.


Fixed in Audiobus SDK 2.1.3 (12 Sep 2014). Third-party apps need to update.
See list of apps already using this SDK version.


iOS 8


Bonjour does not work with only cellular network active

On cellular devices (iPhone, iPad WiFi + Cellular) that are not connected to a WiFi network, Bonjour discovery fails.

This can be seen as apps that continue to appear with "Tap to Launch" label in Audiobus, despite being running and active.

Connect to a WiFi network or enable Airplane Mode.

Fixed in iOS 8.1.

Audio session restore bug


Audiobus SDK

Audio session doesn't restore after interruptions

Audio system may not be restarted after audio session interruptions. This causes audio to stop until apps are restarted.

Close and relaunch all apps, or reboot device.

Fixed in Audiobus SDK 2.1.3 (12 Sep 2014) and Audiobus 2.1.6. Third-party apps need to update.
See list of apps already using this SDK version.