Question

我正在将音频库移植到iOS，以便播放从回调提供的音频流。用户提供了一个返回原始PCM数据的回调，并且我需要播放此数据。而且，该库必须能够一次播放多个流。

我认为我需要使用AVFoundation，但似乎AVAudioPlayer不支持流音频缓冲区，并且所有流文档都可以找到直接来自网络的数据。我应该在这里使用什么API？

谢谢！

顺便说一句，我不是通过Swift或Objective-C使用Apple库。但是我认为一切仍然暴露无遗，因此无论如何都应该感谢Swift中的示例！

Answer 1

您需要初始化：

要使用输入音频单元和输出的音频会话。

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音频引擎

-(SInt32) audioSessionInitialization:(SInt32)preferred_sample_rate {

    // - - - - - - Audio Session initialization
    NSError *audioSessionError = nil;
    session = [AVAudioSession sharedInstance];

    // disable AVAudioSession
    [session setActive:NO error:&audioSessionError];

    // set category - (PlayAndRecord to use input and output session AudioUnits)
   [session setCategory:AVAudioSessionCategoryPlayAndRecord withOptions:AVAudioSessionCategoryOptionDefaultToSpeaker error:&audioSessionError];

   double preferredSampleRate = 441000;
   [session setPreferredSampleRate:preferredSampleRate error:&audioSessionError];

   // enable AVAudioSession
   [session setActive:YES error:&audioSessionError];


   // Configure notification for device output change (speakers/headphones)
   [[NSNotificationCenter defaultCenter] addObserver:self
                                     selector:@selector(routeChange:)
                                         name:AVAudioSessionRouteChangeNotification
                                       object:nil];


   // - - - - - - Create audio engine
   [self audioEngineInitialization];

   return [session sampleRate];
 }

音频引擎回调

-(void) audioEngineInitialization{

    engine = [[AVAudioEngine alloc] init];
    inputNode = [engine inputNode];
    outputNode = [engine outputNode];

    [engine connect:inputNode to:outputNode format:[inputNode inputFormatForBus:0]];


    AudioStreamBasicDescription asbd_player;
    asbd_player.mSampleRate        = session.sampleRate;
    asbd_player.mFormatID            = kAudioFormatLinearPCM;
    asbd_player.mFormatFlags        = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
    asbd_player.mFramesPerPacket    = 1;
    asbd_player.mChannelsPerFrame    = 2;
    asbd_player.mBitsPerChannel    = 16;
    asbd_player.mBytesPerPacket    = 4;
    asbd_player.mBytesPerFrame        = 4;

    OSStatus status;
    status = AudioUnitSetProperty(inputNode.audioUnit,
                              kAudioUnitProperty_StreamFormat,
                              kAudioUnitScope_Input,
                              0,
                              &asbd_player,
                              sizeof(asbd_player));


    // Add the render callback for the ioUnit: for playing
    AURenderCallbackStruct callbackStruct;
    callbackStruct.inputProc = engineInputCallback; ///CALLBACK///
    callbackStruct.inputProcRefCon = (__bridge void *)(self);
    status = AudioUnitSetProperty(inputNode.audioUnit,
                              kAudioUnitProperty_SetRenderCallback,
                              kAudioUnitScope_Input,//Global
                              kOutputBus,
                              &callbackStruct,
                              sizeof(callbackStruct));

    [engine prepare];
}

在iOS上从内存数据流播放音频

1 个答案: