iOS 7 Programming Cookbook

12.3. Recording Audio

Problem

You want to be able to record audio files on an iOS device.

Solution

Use the AVAudioRecorder class in the AV Foundation framework.

Discussion

The AVAudioRecorder class in the AV Foundation framework facilitates audio recording in iOS applications. To start a recording, you need to pass various pieces of information to the initWithURL:settings:error: instance method of AVAudioRecorder:

The URL of the file where the recording should be saved

This is a local URL. The AV Foundation framework will decide which audio format should be used for the recording based on the file extension provided in this URL, so choose the extension carefully.

The settings that must be used before and while recording

Examples include the sampling rate, channels, and other information that will help the audio recorder start the recording. This is a dictionary object.

The address of an instance of NSError where any initialization errors should be saved to

The error information could be valuable later, and you can retrieve it from this instance method in case something goes wrong.

The settings parameter of the initWithURL:settings:error: method is particularly interesting. There are many keys that could be saved in the settings dictionary, but we will discuss only some of the most important ones in this recipe:

AVFormatIDKey

The format of the recorded audio. Some of the values that can be specified for this key are the following:

• kAudioFormatLinearPCM

• kAudioFormatAppleLossless

AVSampleRateKey

The ...