ios - iOS 中的 ExtAudioFileRead 错误代码为 -50

Question

我使用 ExtAudioFileRead 函数将音频文件加载到内存中。但是我发现代码-50总是有错误。这意味着我向函数传递了错误的参数。但是我不知道哪个是错误的参数。

音频文件的数据格式为alac，采样率44100k，有2个声道。

我的代码如下所示:

ExtAudioFileRef recordFile;
OSStatus error = noErr;
error = ExtAudioFileOpenURL((CFURLRef)file, &recordFile);
checkError(error, "open file");

SInt64 frameCount;
UInt32 size = sizeof(frameCount);
error = ExtAudioFileGetProperty(recordFile, kExtAudioFileProperty_FileLengthFrames, &size, &frameCount);
checkError(error, "get frameTotlal");

soundStruct *sound = &_sound;
sound->frameCount = frameCount;
sound->isStereo = true;
sound->audioDataLeft = (SInt16 *)calloc(frameCount, sizeof(SInt16));
sound->audioDataRight = (SInt16 *)calloc(frameCount, sizeof(SInt16));

AudioStreamBasicDescription desc;
UInt32 descSize = sizeof(desc);
error = ExtAudioFileGetProperty(recordFile, kExtAudioFileProperty_FileDataFormat, &descSize, &desc);


[self printASBD:desc];

UInt32 channels = desc.mChannelsPerFrame;

error = ExtAudioFileSetProperty(recordFile, kExtAudioFileProperty_ClientDataFormat, sizeof(inFormat), &inFormat);

AudioBufferList *bufferList;
bufferList = (AudioBufferList *)malloc(sizeof(AudioBufferList) + sizeof(AudioBuffer) * (channels - 1));

AudioBuffer emptyBuff = {0};
size_t arrayIndex;
for (arrayIndex = 0; arrayIndex < channels; arrayIndex ++) {
    bufferList->mBuffers[arrayIndex] = emptyBuff;
}

bufferList->mBuffers[0].mData = sound->audioDataLeft;
bufferList->mBuffers[0].mNumberChannels = 1;
bufferList->mBuffers[0].mDataByteSize = frameCount * sizeof(SInt16);
if (channels == 2) {
    bufferList->mBuffers[1].mData = sound->audioDataRight;
    bufferList->mBuffers[1].mNumberChannels = 1;
    bufferList->mBuffers[1].mDataByteSize = frameCount * sizeof(SInt16);
    bufferList->mNumberBuffers = 2;
}

UInt32 count = (UInt32)frameCount;

error = ExtAudioFileRead(recordFile, &count, bufferList);
checkError(error, "reading");  // Get a -50 error

free(bufferList);
ExtAudioFileDispose(recordFile);

Answer 1

好问题。

当我 ExtAudioFileRead 一个 MONO 文件时，我在对 ExtAudioFileSetProperty 的调用中使用 STEREO 客户端数据格式时发生了这个错误。

我认为 ExtAudioFileRead 不会自动将单声道文件转换为立体声文件，如果存在不匹配，我认为它会失败并出现此 -50 错误。

使单声道文件成为立体声，或为单声道文件设置 inFormat.mChannelsPerFrame=1。

请记住，如果您不进行上转换，则必须通过从单个单声道数据通道写入 L/R channel 来说明音频渲染函数中的单声道文件。