AudioQueue 回调仅在 iOS 7 上获取空缓冲区

Question

我遇到了一个奇怪的问题。我的代码在iOS 5和6上运行良好，但是在iOS 7上运行时，我在AudioQueue回调中得到空缓冲区。

可能的相关代码：

- (void)setUpAudioFormat
{
audioFormat.mFormatID         = kAudioFormatLinearPCM;
audioFormat.mSampleRate       = SAMPLE_RATE;//16000.0;
audioFormat.mChannelsPerFrame = CHANNELS;//1;
audioFormat.mBitsPerChannel   = 16;
audioFormat.mFramesPerPacket  = 1;
audioFormat.mBytesPerFrame    = audioFormat.mChannelsPerFrame * sizeof(SInt16);
audioFormat.mBytesPerPacket   = audioFormat.mBytesPerFrame * audioFormat.mFramesPerPacket;
audioFormat.mFormatFlags      = kLinearPCMFormatFlagIsSignedInteger
| kLinearPCMFormatFlagIsPacked;
bufferNumPackets = 2048;  // must be power of 2 for FFT!
bufferByteSize = [self byteSizeForNumPackets:bufferNumPackets];
}
- (UInt32)numPacketsForTime:(Float64)seconds
{
return (UInt32) (seconds * audioFormat.mSampleRate / audioFormat.mFramesPerPacket);
}
- (UInt32)byteSizeForNumPackets:(UInt32)numPackets
{
return numPackets * audioFormat.mBytesPerPacket;
}
- (void)setUpRecordQueue
{
NSLog(@"n+++ setUpRecordQueue");
OSStatus errorStatus = AudioQueueNewInput(
                   &audioFormat,
                   recordCallback,
                   self,                // userData
                   CFRunLoopGetMain(),  // run loop
                   NULL,                // run loop mode
                   0,                   // flags
                   &recordQueue);
if (errorStatus) {
    NSLog(@"nn ERROR : Error %ld on AudioQueueNewInputn", errorStatus );
}

if (recordQueue == nil) {
    NSLog(@"nn ----- Record Queue is nil! -----");
}
UInt32 trueValue = true;
       AudioQueueSetProperty(recordQueue,kAudioQueueProperty_EnableLevelMetering,&trueValue,sizeof (UInt32));
}
- (void)setUpRecordQueueBuffers
{
NSLog(@"n+++ setUpRecordQueueBuffers");
assert(recordQueue != nil);
for (int t = 0; t < NUMBER_AUDIO_DATA_BUFFERS; ++t)
{
    OSStatus errorStatus = AudioQueueAllocateBuffer(
                             recordQueue,
                             bufferByteSize,
                             &recordQueueBuffers[t]);
    if (errorStatus) {
        NSLog(@"nn ERROR : Error %ld on AudioQueueAllocateBuffern", errorStatus );
    }
}
}
- (void)primeRecordQueueBuffers
{
NSLog(@"n+++ primeRecordQueueBuffers");
assert(recordQueue != nil);
for (int t = 0; t < NUMBER_AUDIO_DATA_BUFFERS; ++t)
{
    OSStatus errorStatus = AudioQueueEnqueueBuffer(
                            recordQueue,
                            recordQueueBuffers[t],
                            0,
                            NULL);
    if (errorStatus) {
        NSLog(@"nn ERROR : Error %ld on AudioQueueEnqueueBuffern", errorStatus );
    }
}
}
- (void)startRecording
{
[self startRecording:FALSE];
}
- (void)startRecording:(BOOL) autoStop
{
NSLog(@"Starting to record");
recording = YES;
shouldStopRecording = NO;
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)
               , ^{
    NSLog(@"PPPP C1");
    _frameIndex= 0;
    self.fileWasCreated = NO;
    [self setUpRecordQueue];
    NSLog(@"PPPP C2");
    [self setUpRecordQueueBuffers];
    NSLog(@"PPPP C3");
    [self primeRecordQueueBuffers];
    NSLog(@"PPPP C4");
    AudioQueueStart(recordQueue, NULL);
    NSLog(@"PPPP C5");
    if (autoStop) {
        [self stopRecording];
    }
});
}
- (void)stopRecording
{
NSLog(@"Stoping to record");
if (recordQueue != nil) {
    NSString *osVersion = [[UIDevice currentDevice]  systemVersion];
    if ([osVersion doubleValue]<6){
        AudioQueueDispose(recordQueue, TRUE);
    }
    else {
        AudioQueueStop(recordQueue, FALSE);
    }
    recordQueue = nil;
}
NSLog(@"Stopped recording");
shouldStopRecording = YES;
recording = NO; 
}

回调：

static void recordCallback(
                       void* inUserData,
                       AudioQueueRef inAudioQueue,
                       AudioQueueBufferRef inBuffer,
                       const AudioTimeStamp* inStartTime,
                       UInt32 inNumPackets,
                       const AudioStreamPacketDescription* inPacketDesc)
{
NSLog(@"recordCallback %u", (unsigned int)inBuffer->mAudioDataByteSize);
// I get always zero here...
}

顺便说一句，麦克风权限正常(启用对麦克风的访问(。

更新：似乎音频队列启动失败，错误为 -50。这仅在 iOS 7 上发生。我设置的参数有任何问题吗？

Answer 1

我发现了问题！ 似乎在iOS 7上也需要设置它(我认为这只是实际的，因此很难找到，没有写在任何地方(。只需在调用任何 AudioQueue 函数之前添加以下代码：

AudioSessionInitialize(NULL,
                       NULL,
                       nil,
                       ( void *)(self)
                       );
UInt32 sessionCategory = kAudioSessionCategory_PlayAndRecord;
AudioSessionSetProperty(kAudioSessionProperty_AudioCategory,
                        sizeof(sessionCategory),
                        &sessionCategory
                        );
AudioSessionSetActive(true);

希望这会帮助其他人。

可以在此处找到另一个可以提供帮助的资源。

Answer 2

@Idan您的答案正确且有效，但仅在应用程序最小部署目标是iOS 7时才显示警告。对于iOS 7，我们可以执行以下操作：

NSError *audioSessionError;
AVAudioSession *audioSession = [AVAudioSession sharedInstance];
[audioSession setCategory:AVAudioSessionCategoryPlayAndRecord error:&audioSessionError];
if(audioSessionError)
{
    NSLog(@"AVAudioSession error setting category:%@",audioSessionError);
}
else
{
    [audioSession setActive:YES error:&audioSessionError];
    if(audioSessionError)
        NSLog(@"AVAudioSession error activating: %@",audioSessionError);
}