IOS8.1调用AudioConvertFillComplexBuffer进行无限循环，cpuload为100%

Question

我正在使用AudioToolBox.AudioConverter库转换音频。

AudioStreamBasicDescription inDescription;
inDescription.mSampleRate = 44100;
inDescription.mFormatID = kAudioFormatMPEGLayer3;
inDescription.mFormatFlags = 0;
inDescription.mBytesPerPacket = 0;
inDescription.mFramesPerPacket = 1152;
inDescription.mBytesPerFrame = 0;
inDescription.mChannelsPerFrame = 2;
inDescription.mBitsPerChannel = 0;
inDescription.mReserved = 0;

AudioStreamBasicDescription outDescription;
audioDescription.mFormatID = kAudioFormatLinearPCM
audioDescription.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked | kAudioFormatFlagsNativeEndian;
audioDescription.mChannelsPerFrame = 2;
audioDescription.mBytesPerPacket = sizeof(SInt16)*audioDescription.mChannelsPerFrame;
audioDescription.mFramesPerPacket = 1;
audioDescription.mBytesPerFrame = sizeof(SInt16)*audioDescription.mChannelsPerFrame;
audioDescription.mBitsPerChannel = 8 * sizeof(SInt16);
audioDescription.mSampleRate = 44100.0;

这是mp3AudioData的转换部分...

AudioBufferList *mp3Audio = (AudioBufferList *)malloc(sizeof(AudioBufferList) + sizeof(AudioBuffer));

mp3Audio->mNumberBuffers = 1;
mp3Audio->mBuffers[0].mNumberChannels  = 2;
mp3Audio->mBuffers[0].mDataByteSize = chunkLen;
mp3Audio->mBuffers[0].mData = calloc(chunkLen, sizeof(uint8_t));
memcpy(mp3Audio->mBuffers[0].mData, chunkData, chunkLen);

AudioStreamPacketDescription *packetDescription =
(AudioStreamPacketDescription*)malloc(sizeof(AudioStreamPacketDescription) * frames);
packetDescription->mDataByteSize = chunkLen;
packetDescription->mStartOffset = 0;
packetDescription->mVariableFramesInPacket = 1;

OSStatus result = AudioConverterFillComplexBuffer(audioConverter,
                                                  fillComplexBufferInputProc,
                                                  &(struct fillComplexBufferInputProc_t) { .bufferList =mp3Audio, .frames = frames, .packetDescriptions = packetDescription },
                                                  &frames,
                                                  pcmAudio,
                                                  NULL);

free(mp3Audio->mBuffers[0].mData);
free(mp3Audio);
free(packetDescription);

第一次运行AudioConverterFillComplexBuffer是正常的，但是当我第二次运行该函数时，无限循环发生了，cpuload 100%。

这段代码在iOS7设备上运行正常，但是当我在iOS8设备上运行它时，无限循环发生了。

谁能告诉我为什么在IOS 8上会发生这种情况？

fillComplexBufferInputProc函数：

static OSStatus fillComplexBufferInputProc(AudioConverterRef             inAudioConverter,
                                           UInt32                        *ioNumberDataPackets,
                                           AudioBufferList               *ioData,
                                           AudioStreamPacketDescription  **outDataPacketDescription,
                                           void                          *inUserData) {
    struct fillComplexBufferInputProc_t *arg = inUserData;

    for (int i = 0; i < ioData->mNumberBuffers; i++) {
        ioData->mBuffers[i].mData = arg->bufferList->mBuffers[i].mData;
        ioData->mBuffers[i].mDataByteSize = arg->bufferList->mBuffers[i].mDataByteSize;
    }

    if (NULL == *outDataPacketDescription) {
        *outDataPacketDescription = arg->packetDescriptions;
    }

    *ioNumberDataPackets = arg->frames;

    return noErr;
}

Answer 1

因为在你的代码中似乎没有无限循环(除了fillComplexBufferInputProc函数中的- loop )，我建议你使用Instruments (Time Profiler)来看看是什么方法占用了大部分的CPU时间。查看堆栈跟踪以获取更多信息，也许我们可以提供帮助。Here是time profiler的教程。