最近有做iOS直播变声的需求，于是去网上搜索了可用的第三方变声库，最终选定了SoundTouch，SoundTouch是C++的一套库，对iOS项目来说也是比较容易进行集成的，具体的可以参考一下 iOS下使用SoundTouch实现变声
要了解变声原理的同学，可以参考一下变声语音相关知识
在使用过程中遇到的最大问题应该是需要SoundTouch进行实时音频流的处理，而目前网上存在的例子，多数都是对音频文件进行处理，于是花了一些时间来适配，这也是今天要说明的重点。
目前在自己的项目中使用音频采集库数据返回的格式是 CMSampleBufferRef，我需要做的是对CMSampleBufferRef进行处理并返回给上层，而看SoundTouch的数据接口 putSamples 能接受的是一个 SAMPLETYPE 类型，继续跟踪查看会发现 SAMPLETYPE 是由以下两个宏定义来决定的
#defineSOUNDTOUCH_INTEGER_SAMPLES1//< 16bit integer samples//#define SOUNDTOUCH_FLOAT_SAMPLES1//< 32bit float samples
因为声音采集的数据格式会有不同，SoundTouch能支持的是16位的int值和32位的float值，接下来我们就需要知道自己的声音采样数据格式是什么样的，这些数据可以从CMSampleBufferRef中来寻找，以下为直接在XCode中打印的一个CMSampleBuffer的值，里面我们可以看到一个 mFormatFlags，目前这个值是0x29，去找AudioFormatFlags的定义可以发现 0x29 = kAudioFormatFlagIsFloat|kAudioFormatFlagIsBigEndian|kAudioFormatFlagIsNonInterleaved，因此可以断定音频数据格式是float类型的，从mBytesPerFrame中可以判断是32位的，这样我们就知道要在代码中打开SOUNDTOUCH_FLOAT_SAMPLES1的定义了
CMSampleBuffer0x14bd9df00retainCount:1allocator:0x1aa381bb8invalid = NO dataReady = YES makeDataReadyCallback =0x0makeDataReadyRefcon =0x0formatDescription = { mediaType:'soun'mediaSubType:'lpcm'mediaSpecific: { ASBD: { mSampleRate:44100.000000mFormatID:'lpcm'mFormatFlags:0x29mBytesPerPacket:4mFramesPerPacket:1mBytesPerFrame:4mChannelsPerFrame:1mBitsPerChannel:32} cookie: {(null)} ACL: {(null)} FormatListArray: {(null)} } extensions: {(null)}} sbufToTrackReadiness =0x0numSamples =941sampleTimingArray[1] = { {PTS = {10672774120541/1000000000=10672.774}, DTS = {INVALID}, duration = {1/44100=0.000}}, } dataBuffer =0x170113b00
接下来需要做的是将数据传给SoundTouch的putSamples，这需要我们从CMSampleBufferRef中来提取音频的数据
voidSoundTouch::putSamples(constSAMPLETYPE*samples,uint nSamples)
下面先贴出原码
- (CMSampleBufferRef)pitchSoundBuffer:(CMSampleBufferRef)ref { AudioBufferList audioBufferList;CMBlockBufferRefblockBuffer;CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(ref,NULL, &audioBufferList,sizeof(audioBufferList),NULL,NULL,0, &blockBuffer); AudioBuffer audioBuffer = audioBufferList.mBuffers[0]; Float32 *frame = (Float32*)audioBuffer.mData;NSMutableData*audioData=[[NSMutableDataalloc] init]; [audioData appendBytes:frame length:audioBuffer.mDataByteSize];char*pcmData = (char*)audioData.bytes;intpcmSize = (int)audioData.length;intnSamples = pcmSize /4; mSoundTouch->putSamples((Float32 *)pcmData, nSamples);if(audioData.length ==0) {returnref; }NSMutableData*soundTouchDatas = [[NSMutableDataalloc] init]; Float32 *samples = new Float32[pcmSize];intnumSamples =0; memset(samples,0, pcmSize); numSamples = mSoundTouch->receiveSamples(samples,nSamples); [soundTouchDatas appendBytes:samples length:numSamples*4]; delete [] samples;CMItemCounttimingCount;CMSampleBufferGetSampleTimingInfoArray(ref,0,nil, &timingCount);CMSampleTimingInfo* pInfo = (CMSampleTimingInfo*)malloc(sizeof(CMSampleTimingInfo) * timingCount);CMSampleBufferGetSampleTimingInfoArray(ref, timingCount, pInfo, &timingCount);if(soundTouchDatas.length ==0) {returnref; }void*touchData = (void*)[soundTouchDatas bytes];CMSampleBufferReftouchSampleBufferRef = [selfcreateAudioSample:touchData frames:(int)[soundTouchDatas length] timing:*pInfo];returntouchSampleBufferRef;}
下面为创建一个CMSampleBufferRef
- (CMSampleBufferRef)createAudioSample:(void*)audioData frames:(UInt32)len timing:(CMSampleTimingInfo)timing{intchannels =1; AudioBufferList audioBufferList; audioBufferList.mNumberBuffers =1; audioBufferList.mBuffers[0].mNumberChannels=channels; audioBufferList.mBuffers[0].mDataByteSize=len; audioBufferList.mBuffers[0].mData = audioData; AudioStreamBasicDescription asbd; asbd.mSampleRate =44100; asbd.mFormatID = kAudioFormatLinearPCM; asbd.mFormatFlags =0x29; asbd.mBytesPerPacket =4; asbd.mFramesPerPacket =1; asbd.mBytesPerFrame =4; asbd.mChannelsPerFrame =1; asbd.mBitsPerChannel =32; asbd.mReserved =0;CMSampleBufferRefbuff =NULL;staticCMFormatDescriptionRefformat =NULL; OSStatus error =0; error =CMAudioFormatDescriptionCreate(kCFAllocatorDefault, &asbd,0,NULL,0,NULL,NULL, &format);if(error) {returnNULL; } error =CMSampleBufferCreate(kCFAllocatorDefault,NULL,false,NULL,NULL, format, len/4,1, &timing,0,NULL, &buff);if(error) {returnNULL; } error =CMSampleBufferSetDataBufferFromAudioBufferList(buff, kCFAllocatorDefault, kCFAllocatorDefault,0, &audioBufferList);if(error){returnNULL; }returnbuff;}
本文出自:https://www.jianshu.com/p/c96a2dd80866