ios - 音频队列录制错误 : AudioConverterNew from AudioQueueNew returned 'fmt?'

Question

这是我设置音频队列服务的代码:

aqData = AQRecorderState()
    aqData.mDataFormat.mFormatID             = kAudioFormatMPEG4AAC
    aqData.mDataFormat.mSampleRate           = 16000.0
    aqData.mDataFormat.mChannelsPerFrame     = 1
    aqData.mDataFormat.mBitsPerChannel       = 16
    aqData.mDataFormat.mBytesPerPacket       = aqData.mDataFormat.mChannelsPerFrame * UInt32(sizeof(UInt16))
    aqData.mDataFormat.mBytesPerFrame        = aqData.mDataFormat.mChannelsPerFrame * UInt32(sizeof(UInt16))
    aqData.mDataFormat.mFramesPerPacket      = 1
    aqData.mDataFormat.mFormatFlags          = kLinearPCMFormatFlagIsFloat | kLinearPCMFormatFlagIsBigEndian
    aqData.mQueue                            = AudioQueueRef()
    fileType                                 = kAudioFileM4AType

    // create new input for audio queue
    AudioQueueNewInput(&aqData.mDataFormat, handleInputBuffer, &aqData, nil, kCFRunLoopCommonModes, 0, &aqData.mQueue)
    var dataFormatSize:UInt32 = UInt32(sizeof(aqData.mDataFormat.dynamicType))
    AudioQueueGetProperty(aqData.mQueue, kAudioQueueProperty_StreamDescription, &aqData.mDataFormat, &dataFormatSize)

    // create file to store audio
    let data = recordUrl.dataUsingEncoding(NSUTF8StringEncoding, allowLossyConversion: false)!
    let audioFileURL: CFURLRef = CFURLCreateFromFileSystemRepresentation(nil, UnsafePointer(data.bytes), data.length, false)
    AudioFileCreateWithURL(audioFileURL, fileType, &aqData.mDataFormat, AudioFileFlags.EraseFile, &aqData.mAudioFile)

    // set magic cookie for file if needed
    setMegicCookieForFile(aqData.mQueue, inFile: aqData.mAudioFile)

    // derive buffer size
    deriveBufferSize(aqData.mQueue, ASBDescription: &aqData.mDataFormat, seconds: kBufferLengthInSecond, outbufferSize: &aqData.bufferByteSize)

    // allocate and enqueue each buffer
    for i in 0..<Record.kNumberBuffers {
        AudioQueueAllocateBuffer(aqData.mQueue, aqData.bufferByteSize, &aqData.mBuffers[i])
        AudioQueueEnqueueBuffer(aqData.mQueue, aqData.mBuffers[i], 0, nil)
    }

代码在行产生错误

AudioQueueNewInput(&aqData.mDataFormat, handleInputBuffer, &aqData, nil, kCFRunLoopCommonModes, 0, &aqData.mQueue)

错误信息是

AudioConverterNew from AudioQueueNew returned 'fmt?'

io:1 channel ，44100 Hz，Float32
客户端:1 channel ，44100 Hz，'aac' (0x00000003) 16 位/ channel ，2 字节/包，1 帧/包，2 字节/帧

我尝试了不同的音频格式设置，但似乎没有一个能修复这个错误。任何人都可以帮忙吗？

Answer 1

来自 CoreAudioTypes.h头文件，我们收集到:

kAudioFormatMPEG4AAC MPEG-4 Low Complexity AAC audio object, has no flags.

并在 AudioStreamBasicDescription 上方发表评论在同一个文件中说:

In compressed audio, a Packet is an indivisible chunk of compressed data, for example an AAC packet will contain 1024 sample frames.

而且由于 AAC 可以是可变比特率(这在 CAF spec 和注释中有所暗示
对于变量 mBytesPerPacket
compressed audio formats ) mBitsPerChannel , mBytesPerPacket和 mFramesPerPacket应该为零。

所以我会尝试更改您的 AudioStreamBasicDescription 的这些字段:

aqData.mDataFormat.mBitsPerChannel       = 0
aqData.mDataFormat.mBytesPerPacket       = 0
aqData.mDataFormat.mBytesPerFrame        = 0
aqData.mDataFormat.mFramesPerPacket      = 1024
aqData.mDataFormat.mFormatFlags          = 0