Overview

This is mainly a test scene to try out various combinations of audio session settings.

Generally, you should set up the audio session settings ONCE, and then use your program. Changing around settings after playing sounds or using iPod playback can cause problems in certain situations, resulting in no sound being output, error messages (especially in OpenAL), and even crashes. You can try changing around live settings in this demo to see what works and what doesn’t, but there’s no guarantee of consistency in Apple’s already obscure implementation.

The buttons are as follows:

Session Active: Controls the audio session’s state (active or not). Once OpenAL initializes, you can’t deactivate the session without first disabling the current OpenAL context.

Suspended: Controls suspending the sound system. This works every time because it first suspends OpenAL and AVAudioPlayer. You need to suspend and resume for some of the audio session settings to take effect.

Allow iPod: When enabled, the application will use software decoding (except in a special case where “Use Hardware” is enabled, see below). This allows it to coexist with iPod music playing.

iPod Ducking: When enabled, causes any iPod style music to decrease in volume while the audio session is active. Note: This only seems to work when “Silent Switch” is disabled.

Silent Switch: Determines whether the app goes silent when the silent switch is turned on. Also prevents sound playback from stopping when the screen locks.

Use Hardware: When enabled, the sound system will attempt to use the hardware decoder if available (no iPod music playing). If the hardware is not being used, the sound system will take it, preventing iPod playback. If the hardware is being used, the sound system will use software decoding.

The “Play/Stop” and “Paused” buttons control looping OpenAL and AVAudioPlayer playback.

BUGS:

There are cases where iOS behaves weirdly, as can be demonstrated here.

Case 1: iPod ducking fails to unduck.

Steps to reproduce: – iPod Ducking: ON – Silent Switch: OFF – Switch to iPod player and start playing. – Suspending/unsuspending causes iPod to duck or unduck. – Playing BOTH an ALSource and an AudioTrack, then suspending, will prevent iPod from unducking.

Case 2: iOS fails to clear interrupt.

Steps to reproduce: – Turn off “Allow iPod”, “Silent Switch”, and “iPod Ducking”. – Switch to the mini ipod player and start it playing. This causes an interrupt. – Stop music in mini ipod player and return to the app. This does NOT clear the interrupt. System is still interrupted and will not play sounds. To clear the interrupt, background the app and then open it again. OALAudioSupport has a method “forceEndInterruption” to help with these sorts of situations.