文字转语音（TTS）iOS7

Question

My application wants to play some text when it is available, and if there is some music playing in the background I want to lower the voice for the music while my app is playing its text, what I did is:

[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback
                                 withOptions:AVAudioSessionCategoryOptionDuckOthers
                                      error:&err];
[[AVAudioSession sharedInstance] setActive:YES error:&err];

The option AVAudioSessionCategoryOptionDuckOthers will lower the music volume while my app is playing its text. Then play the text with the speechSynthesizer , after that in:

- (void)speechSynthesizer:(AVSpeechSynthesizer *)synthesizer didFinishSpeechUtterance:(AVSpeechUtterance *)

utterance I do:

[[AVAudioSession sharedInstance] setActive:NO withFlags:AVAudioSessionSetActiveOptionNotifyOthersOnDeactivation error:nil];

so the music will be back to it original volume.

The problem by setting the session active to NO, I am loosing the volume control (the iPhone hardware volume control the one in the left side of the phone). ie I can not upper or lower the volume for my app unless there is a text actively playing in my app at the moment I am changing the volume.

Answer 1

Thank you very much, It works if I did this, before I play my text:

[[AVAudioSession sharedInstance] setActive:NO withOptions:0 error:nil];
[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback
                                 withOptions:AVAudioSessionCategoryOptionDuckOthers
                                       error:nil];

I had to setActive:NO as without it the second time when I play my text the music will be paused!!

And then After I play my text, I do this:

[[AVAudioSession sharedInstance] setActive:NO withOptions:0 error:nil];
[[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryAmbient withOptions: 0 error: nil];
[[AVAudioSession sharedInstance] setActive:YES withOptions: 0 error:nil];

Answer 2

Immediately after setting setActive: to NO, set it to YES again! Set the category to Ambient so the background sound can continue playing.

So, before you play:

[[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryAmbient
                                 withOptions: AVAudioSessionCategoryOptionDuckOthers
                                       error: nil];
[[AVAudioSession sharedInstance] setActive:YES withOptions: 0 error:nil];

After you play:

[[AVAudioSession sharedInstance] setActive:NO withOptions:0 error:nil];
[[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryAmbient
                                 withOptions: 0
                                       error: nil];
[[AVAudioSession sharedInstance] setActive:YES withOptions: 0 error:nil];