core-audio - m4a 音频文件无法在 iOS 9 上播放

Question

我有一个音频相关的应用程序，它具有多 channel 混音器，可以一次播放 m4a 文件。我正在使用 AudioToolBox 框架来流式传输音频，但在 iOS9 上，该框架在我正在流式传输音频文件的混音器渲染回调中抛出异常。

有趣的是，使用 iOS9 SDK 编译的应用程序继续在 iOS7/8 设备上完美地流式传输相同的文件，但在 iOS9 上则不然。现在我无法确定 Apple 是否在 iOS9 中破坏了某些东西，或者我们的文件编码错误，但它们在 iOS 7/8 上都可以正常播放，但在 iOS 9 上却不行。

异常(exception):

malloc: *** error for object 0x7fac74056e08: incorrect checksum for freed object - object was probably modified after being freed.
*** set a breakpoint in malloc_error_break to debug

它适用于所有其他格式，不会出现任何异常或任何类型的内存错误，但不适用于 m4a 格式，这非常令人惊讶。

这是一个加载文件的代码，适用于 wav、aif 等格式，但不适用于 m4a:

- (void)loadFiles{

    AVAudioFormat *clientFormat = [[AVAudioFormat alloc] initWithCommonFormat:AVAudioPCMFormatFloat32
                                                                   sampleRate:kGraphSampleRate
                                                                     channels:1
                                                                  interleaved:NO];
    for (int i = 0; i < numFiles && i < maxBufs; i++)  {

        ExtAudioFileRef xafref = 0;

        // open one of the two source files
        OSStatus result = ExtAudioFileOpenURL(sourceURL[i], &xafref);
        if (result || !xafref) {break; }

        // get the file data format, this represents the file's actual data format
        AudioStreamBasicDescription fileFormat;
        UInt32 propSize = sizeof(fileFormat);

        result = ExtAudioFileGetProperty(xafref, kExtAudioFileProperty_FileDataFormat, &propSize, &fileFormat);
        if (result) { break; }

        // set the client format - this is the format we want back from ExtAudioFile and corresponds to the format
        // we will be providing to the input callback of the mixer, therefore the data type must be the same

        double rateRatio = kGraphSampleRate / fileFormat.mSampleRate;

        propSize = sizeof(AudioStreamBasicDescription);
        result = ExtAudioFileSetProperty(xafref, kExtAudioFileProperty_ClientDataFormat, propSize, clientFormat.streamDescription);
        if (result) { break; }

        // get the file's length in sample frames
        UInt64 numFrames = 0;
        propSize = sizeof(numFrames);
        result = ExtAudioFileGetProperty(xafref, kExtAudioFileProperty_FileLengthFrames, &propSize, &numFrames);
        if (result) { break; }

        if(i==metronomeBusIndex)
            numFrames = (numFrames+6484)*4;
        //numFrames = (numFrames * rateRatio); // account for any sample rate conversion
        numFrames *= rateRatio;


        // set up our buffer
        mSoundBuffer[i].numFrames = (UInt32)numFrames;
        mSoundBuffer[i].asbd = *(clientFormat.streamDescription);

        UInt32 samples = (UInt32)numFrames * mSoundBuffer[i].asbd.mChannelsPerFrame;
        mSoundBuffer[i].data = (Float32 *)calloc(samples, sizeof(Float32));
        mSoundBuffer[i].sampleNum = 0;

        // set up a AudioBufferList to read data into
        AudioBufferList bufList;
        bufList.mNumberBuffers = 1;
        bufList.mBuffers[0].mNumberChannels = 1;
        bufList.mBuffers[0].mData = mSoundBuffer[i].data;
        bufList.mBuffers[0].mDataByteSize = samples * sizeof(Float32);

        // perform a synchronous sequential read of the audio data out of the file into our allocated data buffer
        UInt32 numPackets = (UInt32)numFrames;

        result = ExtAudioFileRead(xafref, &numPackets, &bufList);
        if (result) {
            free(mSoundBuffer[i].data);
            mSoundBuffer[i].data = 0;
        }

        // close the file and dispose the ExtAudioFileRef
        ExtAudioFileDispose(xafref);
    }

    // [clientFormat release];
}

如果有人能给我指明正确的方向，我该如何着手调试问题？我们是否需要以某种特定方式重新编码我们的文件？

Answer 1

我昨天在 iOS 9.1.beta3 上试了一下，一切似乎都恢复正常了。

尝试一下。让我们知道它是否也适合您。