录音 AudioQueueStart 缓冲区从未填满

Question

我正在使用 AudioQueueStart 以便在 iOS 设备上开始录音，我希望所有录音数据都在缓冲区中流式传输给我，以便我可以处理它们并将它们发送到服务器。

基本功能运行良好，但在我的 BufferFilled 函数中，我通常每次调用都会得到 < 10 字节的数据。这感觉非常低效。特别是因为我试图将缓冲区大小设置为 16384 btyes（请参阅 startRecording 方法的开头）

如何让它在调用 BufferFilled 之前填充更多缓冲区？或者我需要在发送到服务器之前进行第二阶段缓冲以实现我想要的吗？

OSStatus BufferFilled(void *aqData, SInt64 inPosition, UInt32 requestCount, const void *inBuffer, UInt32 *actualCount) {
    AQRecorderState *pAqData = (AQRecorderState*)aqData;

    NSData *audioData = [NSData dataWithBytes:inBuffer length:requestCount];

    *actualCount = inBuffer + requestCount;

    //audioData is ususally < 10 bytes, sometimes 100 bytes but never close to 16384 bytes    


    return 0;
}

void HandleInputBuffer(void *aqData, AudioQueueRef inAQ, AudioQueueBufferRef inBuffer, const AudioTimeStamp *inStartTime, UInt32 inNumPackets, const AudioStreamPacketDescription *inPacketDesc) {
    AQRecorderState *pAqData = (AQRecorderState*)aqData;

    if (inNumPackets == 0 && pAqData->mDataFormat.mBytesPerPacket != 0)
        inNumPackets = inBuffer->mAudioDataByteSize / pAqData->mDataFormat.mBytesPerPacket;

    if(AudioFileWritePackets(pAqData->mAudioFile, false, inBuffer->mAudioDataByteSize, inPacketDesc, pAqData->mCurrentPacket, &inNumPackets, inBuffer->mAudioData) == noErr) {
        pAqData->mCurrentPacket += inNumPackets;
    }

    if (pAqData->mIsRunning == 0)
        return;

    OSStatus error = AudioQueueEnqueueBuffer(pAqData->mQueue, inBuffer, 0, NULL);
}


void DeriveBufferSize(AudioQueueRef audioQueue, AudioStreamBasicDescription *ASBDescription, Float64 seconds, UInt32 *outBufferSize) {
    static const int maxBufferSize = 0x50000;

    int maxPacketSize = ASBDescription->mBytesPerPacket;
    if (maxPacketSize == 0) {
        UInt32 maxVBRPacketSize = sizeof(maxPacketSize);
        AudioQueueGetProperty(audioQueue, kAudioQueueProperty_MaximumOutputPacketSize, &maxPacketSize, &maxVBRPacketSize);
    }

    Float64 numBytesForTime = ASBDescription->mSampleRate * maxPacketSize * seconds;
    *outBufferSize = (UInt32)(numBytesForTime < maxBufferSize ? numBytesForTime : maxBufferSize);
}

OSStatus SetMagicCookieForFile (AudioQueueRef inQueue, AudioFileID   inFile) {
    OSStatus result = noErr;
    UInt32 cookieSize;

    if (AudioQueueGetPropertySize (inQueue, kAudioQueueProperty_MagicCookie, &cookieSize) == noErr) {
        char* magicCookie =
        (char *) malloc (cookieSize);
        if (AudioQueueGetProperty (inQueue, kAudioQueueProperty_MagicCookie, magicCookie, &cookieSize) == noErr)
            result = AudioFileSetProperty (inFile, kAudioFilePropertyMagicCookieData, cookieSize, magicCookie);
        free(magicCookie);
    }
    return result;
}


- (void)startRecording {

    aqData.mDataFormat.mFormatID         = kAudioFormatMPEG4AAC;
    aqData.mDataFormat.mSampleRate       = 22050.0;
    aqData.mDataFormat.mChannelsPerFrame = 1;
    aqData.mDataFormat.mBitsPerChannel   = 0;
    aqData.mDataFormat.mBytesPerPacket   = 0;
    aqData.mDataFormat.mBytesPerFrame    = 0;
    aqData.mDataFormat.mFramesPerPacket  = 1024;
    aqData.mDataFormat.mFormatFlags      = kMPEG4Object_AAC_Main;
    AudioFileTypeID fileType             = kAudioFileAAC_ADTSType;
    aqData.bufferByteSize = 16384;


    UInt32 defaultToSpeaker = TRUE;
    AudioSessionSetProperty(kAudioSessionProperty_OverrideCategoryDefaultToSpeaker, sizeof(defaultToSpeaker), &defaultToSpeaker);

    OSStatus status = AudioQueueNewInput(&aqData.mDataFormat, HandleInputBuffer, &aqData, NULL, kCFRunLoopCommonModes, 0, &aqData.mQueue);
    UInt32 dataFormatSize = sizeof (aqData.mDataFormat);      

    status = AudioQueueGetProperty(aqData.mQueue, kAudioQueueProperty_StreamDescription, &aqData.mDataFormat, &dataFormatSize);
    status = AudioFileInitializeWithCallbacks(&aqData, nil, BufferFilled, nil, nil, fileType, &aqData.mDataFormat, 0, &aqData.mAudioFile);

    for (int i = 0; i < kNumberBuffers; ++i) {
        status = AudioQueueAllocateBuffer (aqData.mQueue, aqData.bufferByteSize, &aqData.mBuffers[i]);
        status = AudioQueueEnqueueBuffer (aqData.mQueue, aqData.mBuffers[i], 0, NULL);
    }

    aqData.mCurrentPacket = 0;                           
    aqData.mIsRunning = true;                            

    status = AudioQueueStart(aqData.mQueue, NULL);
}

更新： 我已经记录了我收到的数据，这很有趣，几乎 "packets" 的一半似乎是某种 header 一半是声音数据。我可以假设这就是 iOS 上的 AAC 编码的工作原理吗？它在一个缓冲区中写入 header，然后在下一个缓冲区中写入数据，依此类推。而且它从不希望每个数据块超过 170-180 字节，这就是为什么它忽略我的大缓冲区？

Answer 1

我最终解决了这个问题。结果是 iOS 上的编码产生了小块和大块数据。我自己使用 NSMutableData 添加了一个第二阶段缓冲区，它运行良好。

录音 AudioQueueStart 缓冲区从未填满

Audio Recording AudioQueueStart buffer never filled

ios

objective-c

iphone

cocoa-touch

aac