我写了一个使用“novocaine”库来录制和播放声音的voip应用程序。我将采样率设置为8kHz。此采样率在音频单元的AudioStreamBasicDescription中设置为novocaine,并设置为音频会话属性kAudioSessionProperty_PreferredHardwareSampleRate。据我所知,设置首选硬件采样率并不能保证实际的硬件采样率会发生变化,但它适用于除iPhone6s和iPhone6s +之外的所有设备(当路由更改为扬声器时)。通过iPhone6s(+)和扬声器路线,我可以收到来自麦克风的48kHz声音。所以我需要以某种方式将这个48kHz的声音转换成8kHz。在文档中,我发现AudioConverterRef可以在这种情况下使用,但是我使用它时遇到麻烦。AudioConverterRef采样率转换(iOS)
我使用AudioConverterFillComplexBuffer进行采样率转换,但它总是返回-50 OSStatus(传递给函数的一个或多个参数无效)。这是我如何使用音频转换器:
// Setup AudioStreamBasicDescription for input
inputFormat.mSampleRate = 48000.0;
inputFormat.mFormatID = kAudioFormatLinearPCM;
inputFormat.mFormatFlags = kAudioFormatFlagIsFloat | kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked;
inputFormat.mChannelsPerFrame = 1;
inputFormat.mBitsPerChannel = 8 * sizeof(float);
inputFormat.mFramesPerPacket = 1;
inputFormat.mBytesPerFrame = sizeof(float) * inputFormat.mChannelsPerFrame;
inputFormat.mBytesPerPacket = inputFormat.mBytesPerFrame * inputFormat.mFramesPerPacket;
// Setup AudioStreamBasicDescription for output
outputFormat.mSampleRate = 8000.0;
outputFormat.mFormatID = kAudioFormatLinearPCM;
outputFormat.mFormatFlags = kAudioFormatFlagIsFloat | kAudioFormatFlagsNativeEndian | kAudioFormatFlagIsPacked;
outputFormat.mChannelsPerFrame = 1;
outputFormat.mBitsPerChannel = 8 * sizeof(float);
outputFormat.mFramesPerPacket = 1;
outputFormat.mBytesPerFrame = sizeof(float) * outputFormat.mChannelsPerFrame;
outputFormat.mBytesPerPacket = outputFormat.mBytesPerFrame * outputFormat.mFramesPerPacket;
// Create new instance of audio converter
AudioConverterNew(&inputFormat, &outputFormat, &converter);
// Set conversion quality
UInt32 tmp = kAudioConverterQuality_Medium;
AudioConverterSetProperty(converter, kAudioConverterCodecQuality,
sizeof(tmp), &tmp);
AudioConverterSetProperty(converter, kAudioConverterSampleRateConverterQuality, sizeof(tmp), &tmp);
// Get the size of the IO buffer(s)
UInt32 bufferSizeFrames = 0;
size = sizeof(UInt32);
AudioUnitGetProperty(self.inputUnit,
kAudioDevicePropertyBufferFrameSize,
kAudioUnitScope_Global,
0,
&bufferSizeFrames,
&size);
UInt32 bufferSizeBytes = bufferSizeFrames * sizeof(Float32);
// Allocate an AudioBufferList plus enough space for array of AudioBuffers
UInt32 propsize = offsetof(AudioBufferList, mBuffers[0]) + (sizeof(AudioBuffer) * outputFormat.mChannelsPerFrame);
// Malloc buffer lists
convertedInputBuffer = (AudioBufferList *)malloc(propsize);
convertedInputBuffer->mNumberBuffers = 1;
// Pre-malloc buffers for AudioBufferLists
convertedInputBuffer->mBuffers[0].mNumberChannels = outputFormat.mChannelsPerFrame;
convertedInputBuffer->mBuffers[0].mDataByteSize = bufferSizeBytes;
convertedInputBuffer->mBuffers[0].mData = malloc(bufferSizeBytes);
memset(convertedInputBuffer->mBuffers[0].mData, 0, bufferSizeBytes);
// Setup callback for converter
static OSStatus inputProcPtr(AudioConverterRef inAudioConverter,
UInt32* ioNumberDataPackets,
AudioBufferList* ioData,
AudioStreamPacketDescription* __nullable* __nullable outDataPacketDescription,
void* __nullable inUserData)
{
// Read data from buffer
}
// Perform actual sample rate conversion
AudioConverterFillComplexBuffer(converter, inputProcPtr, NULL, &numberOfFrames, convertedInputBuffer, NULL)
inputProcPtr回调永远不会被调用。我试图设置不同数量的帧,但仍然收到OSStatus -50。
1)使用AudioConverterRef是否是正确的方式来进行采样率转换或可以以不同的方式完成?
2)我的转换实现有什么问题?
谢谢大家提前