Question

我想要做的是让我的应用在背景音频应用播放音频时使用AVSpeechSynthesizer说出话语。当我的应用发言时，我希望后台应用的音频“昏暗”，然后在我的应用完成发言后返回原始音量。

在我的AudioFeedback课程中，我初始化我设置AVAudioSessions，如下所示：

    self.session = [AVAudioSession sharedInstance];
    NSError *error;
    [self.session setCategory:AVAudioSessionCategoryPlayback withOptions:AVAudioSessionCategoryOptionDuckOthers error:&error];

每当我想说一个新话语时，我都会做以下事情。我遵循An issue with AVSpeechSynthesizer, Any workarounds?的建议，每次都要创建一个新的AVSpeechSynthesizer，以“确保”始终收到取消（它似乎有效，我不知道为什么）。

- (AVSpeechUtterance *) utteranceWithString: (NSString *) string
{
    AVSpeechUtterance *utterance = [AVSpeechUtterance  speechUtteranceWithString:string];
    utterance.voice = [AVSpeechSynthesisVoice voiceWithLanguage:@"en-ES"];
    [utterance setRate:(AVSpeechUtteranceDefaultSpeechRate+AVSpeechUtteranceMinimumSpeechRate)/2.0];
    return utterance;
}

- (void) sayString: (NSString *) string cancelPrevious: (BOOL) cancelPrevious
{
    [self.session setActive:enabled error:nil];
    if (cancelPrevious) {
        AVSpeechSynthesizer *oldSynthesizer = self.voice;
        self.voice = nil;
        [oldSynthesizer stopSpeakingAtBoundary:AVSpeechBoundaryImmediate];
        self.voice = [[AVSpeechSynthesizer alloc] init];
        self.voice.delegate = self;
    }

    // Keep track of the final utterance, we'll use this to determine whether or not we should stop the audio session
    self.finalUtterance = [self utteranceWithString:string];
    [self.voice speakUtterance:self.finalUtterance];
}

在我的AVSpeechSynthesizer委托方法中，如果当前的AVSpeechSynthesizer和当前的AVSpeechUtterance与最后已知的合成器和话语匹配，我会检查是否应该停止音频会话以将背景音频恢复为正常音量。

-(void)speechSynthesizer:(AVSpeechSynthesizer *)synthesizer didFinishSpeechUtterance:(AVSpeechUtterance *)utterance
{
    NSError *error;
    // Only stop the audio session if this is the last created synthesizer
    if (synthesizer == self.voice  && self.finalUtterance == utterance) {
        if ([self.session setActive:enabled error:&error]]) {
            NSLog(@"Stopped the audio session: Speech synthesizer still speaking %d", synthesizer.speaking);
        } else {
            NSLog(@"ERROR failed to stop the audio session: %@. Speech synthesizer still speaking %d", error, synthesizer.speaking);
        }
    }
}

我遇到的问题是，有时，音频会话会在没有问题的情况下停止，有时，音频会话将无法停止并出现以下错误：

错误域= NSOSStatusErrorDomain代码= 2003329396“操作无法完成。（OSStatus错误2003329396。）”

我不确定如何保证我可以停止AVAudioSession。只要我无法停止音频会话，我就试着继续呼叫[[AVAudioSession sharedInstance] setActive:NO error:&error]，但这似乎不起作用。任何帮助将不胜感激。谢谢！

Answer 1

我发现如果我在几秒钟内再试一次它会起作用。我正在使用此代码。

-(void)configureAVAudioSession:(bool)active {

    AVAudioSession *audioSession = [AVAudioSession sharedInstance];

    if (deactivationAttempt < 3) {  // This doesn't always work first time, but don't want to keep trying forever if it decides not to work ever.

        NSError *activationError = nil;
        success = [audioSession setActive:active error:&activationError];

        if (!success) {
            NSLog(@"(de)activation ERROR");
            ++deactivationAttempt;
            [self performSelector:@selector(configureAVAudioSession:) withObject:false afterDelay:2.0];
        }
        else {  // Success!
            deactivationAttempt = 0;
        }
    }
    else {  // Failed, but reset the counter in case we have more luck next time
        deactivationAttempt = 0;
    }
}

来自文档：

如果当前正在运行任何关联的音频对象（例如队列，转换器，播放器或录像机），则取消激活会话将失败。

我想从队列中清除话语需要一段时间。

Answer 2

我遇到了同样的问题，我相信我找到了原因。对我而言，如果我所说的短语太短，则会给出错误。如果它“足够长”，则没有错误。

我测试了

NSString *phraseToSay = [NSString stringWithFormat:@"One Two Three Four Five"]; // Gives the error
NSString *phraseToSay = [NSString stringWithFormat:@"One Two Three Four Five Six"]; // No error

我找到的唯一解决方案是使短语更长。

如何在AVSpeechUtterance之后始终停止AVAudioSession

2 个答案: