CODEWITHSUNDEEP
javascriptiosuiwebviewweb-audio-api
gabrielmaldi
gabrielmaldi

Reputation: 2196

Web Audio API in UIWebView stops Music app's current song

A simple usage of the Web Audio API:

var UnprefixedAudioContext = window.AudioContext || window.webkitAudioContext;

var context;
var volumeNode;
var soundBuffer;

context = new UnprefixedAudioContext();
volumeNode = context.createGain();
volumeNode.connect(context.destination);
volumeNode.gain.value = 1;

context.decodeAudioData(base64ToArrayBuffer(getTapWarm()), function (decodedAudioData) {
    soundBuffer = decodedAudioData;
});

function play(buffer) {
    var source = context.createBufferSource();
    source.buffer = buffer;
    source.connect(volumeNode);
    (source.start || source.noteOn).call(source, 0);
};

function playClick() {
    play(soundBuffer);
}

inside a UIWebView works fine (plays the sound); but when you switch to the Music app and play a song, and then come back to the app with the UIWebView the song stops playing.

The same code inside Safari doesn't have this problem.

Is there a workaround to avoid this behavior?

Here's the full fiddle:

http://jsfiddle.net/gabrielmaldi/4Lvdyhpx/

Upvotes: 0

Views: 1054

Answers (1)

morgancodes
morgancodes

Reputation: 25265

Are you on iOS? This sounds like an audio session category issue to me. iOS apps define how their audio interacts with audio. From Apple's documentation:

Each audio session category specifies a particular pattern of “yes” and “no” for each of the following behaviors, as detailed in Table B-1:

Interrupts non-mixable apps audio: If yes, non-mixable apps will be interrupted when your app activates its audio session.

Silenced by the Silent switch: If yes, your audio is silenced when the user moves the Silent switch to silent. (On iPhone, this switch is called the Ring/Silent switch.)

Supports audio input: If yes, app audio input (recording), is allowed.

Supports audio output: If yes, app audio output (playback), is allowed.

Looks like the default category silences audio from other apps:

AVAudioSessionCategorySoloAmbient—(Default) Playback only. Silences audio when the user switches the Ring/Silent switch to the “silent” position and when the screen locks. This category differs from the AVAudioSessionCategoryAmbient category only in that it interrupts other audio.

The key here is in the last sentence: "it interrupts other audio".

There are a number of other categories you can use depending on whether or not you want your audio silenced when the screen is locked, etc. AVAudioSessionCategoryAmbient does not silence audio.

Give this a try in the objective-c portion of your app:

NSError *setCategoryError = nil;

BOOL success = [[AVAudioSession sharedInstance]
                setCategory: AVAudioSessionCategoryAmbient
                      error: &setCategoryError];

if (!success) { /* handle the error in setCategoryError */ }

Upvotes: 2

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