Question

我有一个名为_recordingSamples的Float32值数组，我希望将其写入音频文件。 _recordingLength的值大约是390000.我使用以下代码：

NSString *outputPath = @"/Users/evanjackson/output.caf";
NSFileManager *fileManager = [NSFileManager defaultManager];
[fileManager createFileAtPath:outputPath contents:nil attributes:nil];

AudioStreamBasicDescription _audioFormat;
_audioFormat.mSampleRate = 44100.0;
_audioFormat.mFormatID = kAudioFormatLinearPCM;
_audioFormat.mFormatFlags = kAudioFormatFlagsNativeFloatPacked;
_audioFormat.mChannelsPerFrame = 1;
_audioFormat.mBitsPerChannel = 32;
_audioFormat.mBytesPerFrame = 4;
_audioFormat.mFramesPerPacket = 1;
_audioFormat.mBytesPerPacket = _audioFormat.mFramesPerPacket * _audioFormat.mBytesPerFrame;

UInt32 lengthPropertySize = sizeof(SInt64);
ExtAudioFileRef filteredAudio;
NSURL *destinationURL = [NSURL URLWithString:outputPath];
OSStatus status = ExtAudioFileCreateWithURL((__bridge CFURLRef)destinationURL, kAudioFileCAFType, &_audioFormat, NULL, kAudioFileFlags_EraseFile, &filteredAudio);
printf("Status: %d\n", status);
//ExtAudioFileOpenURL((__bridge CFURLRef)[NSURL fileURLWithPath:outputPath], &filteredAudio);
const AudioStreamBasicDescription audioFormat = [del audioFormat];
status = ExtAudioFileSetProperty(filteredAudio, kExtAudioFileProperty_ClientDataFormat, sizeof(audioFormat), &audioFormat);
printf("Status: %d\n", status);
status = ExtAudioFileGetProperty(filteredAudio, kExtAudioFileProperty_FileLengthFrames, &lengthPropertySize, &_recordingLength);
printf("Status: %d\n", status);
AudioBufferList *buffers = (AudioBufferList *)malloc(sizeof(AudioBufferList) + sizeof(AudioBuffer));
buffers->mNumberBuffers = 1;
for (int i = 0; i < buffers->mNumberBuffers; i++) {
    buffers->mBuffers[0].mData = _recordingSamples;
    buffers->mBuffers[0].mNumberChannels = 1;
    buffers->mBuffers[0].mDataByteSize = _recordingLength * sizeof(Float32);
}

status = ExtAudioFileWrite(filteredAudio, _recordingLength, buffers);
printf("Status: %d\n", status);

所有状态都返回0，文件被创建（4个字节）但Quicktime不会打开它并返回错误-12842，编译器发出以下消息：

libc++abi.dylib: terminating with uncaught exception of type std::bad_alloc: std::bad_alloc
(lldb)

有人知道出了什么问题吗？提前谢谢。

Answer 1

废弃我在问题中发布的代码。我在这里找到了解决方案：How to write array of float values to audio file in Core Audio?。看看第一个答案。我转到给定的链接，下载了源代码，然后将EAFWrite.h和EAFWrite.mm添加到我的项目中。该类假定音频将从多个缓冲区（即：2D数组）中读取，但需要它与1D数组一起使用，因此我修改了函数writeToFloats，如下所示：

-(OSStatus) writeFloats:(long)numFrames fromArray:(float *)data
{
    OSStatus    err = noErr;

    if (!data)      return -1;
    if (!numFrames) return -1;

    AudioBufferList *abl = AllocateAudioBufferList(mStreamFormat.mChannelsPerFrame, numFrames*sizeof(short));
    if (!abl)       return -1;

    abl->mBuffers[0].mNumberChannels = 1;
    abl->mBuffers[0].mDataByteSize = numFrames*sizeof(short);
    short *buffer = (short*)abl->mBuffers[0].mData;
    for (long v = 0; v < numFrames; v++) {
        if (data[v] > 0.999)
            data[v] = 0.999;
        else if (data[v] < -1)
            data[v] = -1;
        buffer[v] = (short)(data[v]*32768.f);
    }

    abl->mBuffers[0].mData = buffer;

    err = ExtAudioFileWrite(mOutputAudioFile, numFrames, abl);

    DestroyAudioBufferList(abl);

    if(err != noErr)
    {
        char formatID[5];
        *(UInt32 *)formatID = CFSwapInt32HostToBig(err);
        formatID[4] = '\0';
        fprintf(stderr, "ExtAudioFileWrite FAILED! %d '%-4.4s'\n",(int)err, formatID);
        return err;
    }

    return err;

}

要调用此功能，您需要：

NSString *outputPath = @"outputFile.caf"
NSFileManager *fileManager = [NSFileManager defaultManager];
[fileManager createFileAtPath:outputPath contents:nil attributes:nil];
NSURL* fileURL = [NSURL URLWithString:outputPath];

EAFWrite *writer = [[EAFWrite alloc] init];
[writer openFileForWrite:fileURL sr:44100.0 channels:1 wordLength:32 type:kAudioFileCAFType];
[writer writeFloats:_recordingLength fromArray:_recordingSamples];

Answer 2

这是一堆相当毛茸茸的代码。

这一行：

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

对我来说很可疑。它正在分配一个固定大小的缓冲区，即sizeof（AudioBufferList）和sizeof（AudioBuffer）的总和

这两个变量有哪些类型？

Sizeof返回结构的大小，而不是它指向的内容的大小。我猜你需要一个缓冲区，分配给一个浮点数的大小乘以一个值，该值保存数组中浮点数的总数。（这是_recordingLength？）

这段代码来自哪里？你能详细解释一下它应该做些什么吗？你的花车阵列来自哪里？什么告诉你的代码有多少字节？数据存储在内存中的哪个位置？什么将值缓冲区写入磁盘？

您说您的文件已创建并且长度为4个字节。如果你试图存储大约390000个花车，这听起来确实是一个问题。

将浮点数组写入音频文件

2 个答案: