AV Foundation Cocoa Conf Chicago 2014

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All the Audio You Need Beginners Guide to AV Foundation Audio

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Remedial Core Audio 101

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Foundations of Core Audio Audio Queue Audio Session Audio Unit

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– Jens Alfke, quoted from the Core Audio Mailing List “"Easy" and "CoreAudio" can't be used in the same sentence. :P CoreAudio is very powerful, very complex, and under-documented. Be prepared for a steep learning curve, APIs with millions of tiny little pieces, and puzzling things out from sample code rather than reading high-level documentation.”

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– Q “If you can't take a little bloody nose, maybe you ought to go back home and crawl under your bed. It's not safe out here. It's wondrous, with treasures to satiate desires both subtle and gross. But it's not for the timid.”

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So what do we do??

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System Sound Services and AVFoundation!!

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Here is how to add Sound to your app in less than two minutes (which I found out by accident at my last talk…)

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Demo

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System Sound Services

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System Sound Services

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System Sound Services

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Wait a second, this is supposed to just be about AVFoundation!! What gives??

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So, that’s cool, but it’s kind of limited, isn’t it??? ! Also, didn’t you promise me there would be no C??

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AV Foundation

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What is AV Foundation? AV Foundation is one of several frameworks that you can use to play and create time-based audiovisual media. It provides an Objective-C interface you use to work on a detailed level with time-based audiovisual data.

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Advantages of AV Foundation Built-in interruption handling Written in Objective-C Optimized for the iOS ecosystem Now powerful enough to do much of what Core Audio does

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AV Foundation Audio Classes AVAudioSession AVAudioPlayer AVAudioRecorder

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AVAudioSession AVAudioSession is a singleton object that comes included into your projects regardless of whether you create one or not. AVAudioSession manages all of the other AV Audio objects.

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AVAudioSession Activate/Deactivate the audio session Set the audio session category Configure audio settings Handle audio route changes and react to audio events

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Audio Session Default Behavior Playback Enabled, Recording Disabled “Silent” switch mutes your sound When the phone sleeps your sound stops When your audio starts other audio, like iTunes, stops playing.

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When Can I Ignore the Audio Session? If you are using System Sound Services or UIKit playInputClick If you do not use sound at all

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Audio Session Categories AVAudioSessionCategorySoloAmbient (default) AVAudioSessionCategoryAmbient AVAudioSessionCategoryPlayback AVAudioSessionCategoryRecord

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Audio Session Categories AVAudioSessionCategoryPlayAnd Record AVAudioSessionCategoryAudio Processing AVAudioSessionCategoryMultiRoute

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AV Audio Session Category Audio Processing No input or output Processes audio offline Only really going to be used in a specialized audio app

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AV Audio Session Category MultiRoute Used to send sound to more than one output (disk, headphones, speaker, etc…) FYI: The default audio route is to the phone receiver, you can override this to go to the speaker on the bottom of the phone

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AV Audio Session Category Ambient Silenced by the mute switch Allows audio mixing from other apps, like iTunes Output only

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AV Audio Session Category Solo Ambient Silenced by the mute switch Does NOT allow audio mixing from other apps Output Only

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Demo

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Ambient vs Solo Ambient

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AV Audio Session Category Playback Is NOT silenced by the mute switch Does not allow other audio by default, but you can override this behavior Output only

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AVAudioPlayer Delegate Has built-in methods to handle interruptions from phone calls and alerts.

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Demo

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Ready Player One Demo

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Ready Player One Demo

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Ready Player One Demo

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Ready Player One Demo

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Ready Player One Demo

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Ready Player One Demo

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Ready Player One Demo

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AV Audio Session Category Record Input only, so it is not affected by the mute switch and it does not allow audio from other apps I find this to be limiting and would recommend the next category instead.

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AV Audio Session Category Play and Record Is NOT silenced by the mute switch Does not allow other audio by default, but you can override this behavior Both Input and Output

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Demo

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Recorder Demo

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Recorder Demo

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Recorder Demo

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Recorder Demo

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I [insert name here]…

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Do solemnly swear…

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Never to use my laptop microphone…

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For anything I intend for human consumption…

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So help me Jobs.

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AVAudioRecorder Delegate Does NOT allow phone calls to go through, so there is no error handling for phone calls.

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Quiz Time!! Scenario 1: You are writing an audio book app. You need to make sure the audio keeps playing when the device falls asleep. What category should you use?

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Choices: A: AVAudioSessionCategoryAmbient B: AVAudioSessionCategoryPlayback C: System Sound Services with AVAudioSessionCategorySoloAmbient

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Quiz Time!! Answer: B AVAudioSessionCategoryPlayback

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Quiz Time! Scenario 2: You are building an app.Net client and you want to add a sound effect when the user publishes a post.

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Choices: A: AVAudioSessionCategoryAmbient B: AVAudioSessionCategoryPlayback C: System Sound Services with AVAudioSessionCategorySoloAmbient

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Quiz Time! Answer: C   System Sound Services with AVAudioSessionCategorySoloAmbient

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Quiz Time! Scenario 3: You write a first-person shooter game that uses OpenAL- based sound effects. You also provide a background soundtrack but include an option for the user to turn it off. What session type do you use?

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Choices: A: AVAudioSessionCategoryAmbient B: AVAudioSessionCategoryPlayback C: System Sound Services with AVAudioSessionCategorySoloAmbient

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Quiz Time! Answer: A AVAudioSessionCategoryAmbient

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How to Choose Your Audio Category Think about the primary purpose for audio in your app Is your audio essential or peripheral? How likely is it that other audio will be playing when your app is launched?