iOS 音频录制

iOS实现音频录制常用的三种方式

录制之前应对AVAudioSeeion进行设置

AVAudioSession *audioSession = [AVAudioSession sharedInstance]; [audioSession setCategory:AVAudioSessionCategoryRecord error:nil]; //设置为录音模式, 如果需要可以对采样率sampleRate，缓冲时长ioBufferDuration等进行设置 [audioSession setActive:YES error:nil];

1、AVAudioRecorder：

    AVAudioRecorder的使用相对比较简单 NSError *error; NSDictionary *settings = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithInt:kAudioFormatLinearPCM], AVFormatIDKey, [NSNumber numberWithFloat:8000], AVSampleRateKey, [NSNumber numberWithInt:2], AVNumberOfChannelsKey, [NSNumber numberWithInt:16], AVLinearPCMBitDepthKey, [NSNumber numberWithBool:NO], AVLinearPCMIsNonInterleaved, [NSNumber numberWithBool:NO],AVLinearPCMIsFloatKey, [NSNumber numberWithBool:NO], AVLinearPCMIsBigEndianKey,nil]; AVAudioRecorder *recorder = [[AVAudioRecorder alloc] initWithURL:[NSURL fileURLWithPath:filePath] settings:settings error:&error]; if (error) { 查看具体原因 } recorder.delegate = self; if ([recorder prepareToRecord]) { [recorder record]; }

这样就实现简单的音频录制。当然AVAudioRecorder还提供了暂停，继续等功能，代理中有录制完成、出错等回掉信息。

2、AVCaptureSession：

_captureSession = [[AVCaptureSession alloc] init]; AVCaptureDevice *devices = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio]; NSError *error; _deviceInput = [[AVCaptureDeviceInput alloc] initWithDevice:devices error:&error]; if ([_captureSession canAddInput: _deviceInput]) { // 添加输入设备 [_captureSession addInput:_deviceInput]; }

利用AVCaptureAudioFileOutput自动将音频写入文件

_audioFileOutput = [[AVCaptureAudioFileOutput alloc] init]; if ([_captureSession canAddOutput:_audioFileOutput]) { [_captureSession addOutput:_audioFileOutput]; } [self.audioFileOutput setAudioSettings:settings]; [self.audioFileOutput startRecordingToOutputFileURL:[NSURL fileURLWithPath:filePath] outputFileType:AVFileTypeCoreAudioFormat recordingDelegate:self]; #pragma mark - 代理 - 必须实现 - (void)captureOutput:(AVCaptureFileOutput *)output didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL fromConnections:(NSArray<AVCaptureConnection *> *)connections error:(nullable NSError *)error { // 这里是录制完成的回掉， 在这里可以进行文件移动、转码等操作。 }

利用AVAssetWriter将录制的音频流写入文件

_audioFileOutput = [[AVCaptureAudioDataOutput alloc] init]; //获取音频流，自己进行写入 [_audioFileOutput setSampleBufferDelegate:self queue:_audioOutQueue]; if ([_captureSession canAddOutput:_audioFileOutput]) { [_captureSession addOutput:_audioFileOutput]; } NSError *error; _asset = [[AVAssetWriter alloc] initWithURL:[NSURL fileURLWithPath:filePath] fileType:AVFileTypeCoreAudioFormat error:&error]; _assetWriteInput = [[AVAssetWriterInput alloc] initWithMediaType:AVMediaTypeAudio outputSettings:settings]; _assetWriteInput.expectsMediaDataInRealTime = YES; if ([_asset canAddInput:_assetWriteInput]) { [_asset addInput:_assetWriteInput]; } #pragma mark - 数据回掉 - (void)captureOutput:(AVCaptureOutput *)output didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection { if (_asset.status != AVAssetWriterStatusWriting) { CMTime lastSampleTime = CMSampleBufferGetPresentationTimeStamp(sampleBuffer); if (![_asset startWriting]) { NSLog(@"%@", _asset.error.localizedDescription); } [_asset startSessionAtSourceTime:lastSampleTime]; } if (_asset.status == AVAssetWriterStatusWriting) { [self.assetWriteInput appendSampleBuffer:sampleBuffer]; } }

3、AudioUnit：

static void CheckStatus(OSStatus status, NSString *errMsg, BOOL fatal) { //操作结果判断 if (status != noErr) { char fourcc[16]; *fourcc = CFSwapInt32HostToBig(status); fourcc[4] = '\0'; if (isprint(fourcc[0]) && isprint(fourcc[1]) && isprint(fourcc[2]) && isprint(fourcc[3])) { NSLog(@"%@ : %s", errMsg, fourcc); } else { NSLog(@"%@ : %d", errMsg, (int)status); } if (fatal) { exit(-1); } } }

AudioUnit初始化

AudioComponentDescription description; description.componentType = kAudioUnitType_Output; //录音一般选择Output, 除此之外还有Effect、FormatConverter等多种对音频进行解码、混音、变身等操作 description.componentSubType = kAudioUnitSubType_RemoteIO;//type对应的子类型 description.componentFlags = 0; description.componentFlagsMask = 0; description.componentManufacturer = kAudioUnitManufacturer_Apple;//厂商 _ioUnitRef = AudioComponentFindNext(NULL, &description); CheckStatus(AudioComponentInstanceNew(_ioUnitRef, &_audioUnit), @"初始化音频单元失败", NO);

AudioUnit配置

UInt32 flag = 1; CheckStatus(AudioUnitSetProperty(_audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, ElementOne, &flag, sizeof(flag)), @"打开麦克风成功", NO); /** AudioStreamBasicDescription: 这里描述与前两种录制方式中的settings大多相同 mSampleRate; 采样率, eg. 44100 mFormatID; 格式, eg. kAudioFormatLinearPCM mFormatFlags; 标签格式, eg. kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked mBytesPerPacket; 每个Packet的Bytes数量 mFramesPerPacket; 每个Packet的帧数量 mBytesPerFrame; 每帧的Byte数 mChannelsPerFrame; 1:单声道；2:立体声 mBitsPerChannel; 语音每采样点占用位数[8/16/24/32] mReserved; 保留 */ _streamDescription.mFormatID = kAudioFormatLinearPCM; _streamDescription.mSampleRate = 44100.00; _streamDescription.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsNonInterleaved; _streamDescription.mChannelsPerFrame = 1; _streamDescription.mFramesPerPacket = 1; _streamDescription.mBitsPerChannel = 16; _streamDescription.mBytesPerFrame = 2; _streamDescription.mBytesPerPacket = 2; CheckStatus(AudioUnitSetProperty(_audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, ElementOne, &_streamDescription, sizeof(_streamDescription)), @"设置输出音频参数成功", NO); AURenderCallbackStruct renderCallbackStruct; renderCallbackStruct.inputProc = recordingCallback; renderCallbackStruct.inputProcRefCon = (__bridge void *)self; CheckStatus(AudioUnitSetProperty(_audioUnit, kAudioOutputUnitProperty_SetInputCallback, kAudioUnitScope_Global, ElementOne, &renderCallbackStruct, sizeof(renderCallbackStruct)), @"设置录音回掉", NO); NSString *destinationFilePath = [[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"] stringByAppendingPathComponent:@"test.caf"]; CFURLRef urlRef = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, (CFStringRef)destinationFilePath, kCFURLPOSIXPathStyle, false); CheckStatus(ExtAudioFileCreateWithURL(urlRef, kAudioFileCAFType, &_streamDescription, NULL, kAudioFileFlags_EraseFile, &_audioFileRef), @"创建文件成功", NO); CFRelease(urlRef); static OSStatus recordingCallback(void *inRefCon, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData) { ViewController *controller = (__bridge ViewController *)inRefCon; AudioBufferList bufferList; bufferList.mNumberBuffers = 1; bufferList.mBuffers[0].mNumberChannels = 1; bufferList.mBuffers[0].mDataByteSize = 2 * inNumberFrames; //缓冲区大小 bufferList.mBuffers[0].mData = malloc(inNumberFrames * 2); CheckStatus(AudioUnitRender(controller->_audioUnit, ioActionFlags, inTimeStamp, inBusNumber, inNumberFrames, &(bufferList)), @"获取数据成", NO); CheckStatus(ExtAudioFileWrite(controller->_audioFileRef, inNumberFrames, &bufferList), @"写入文件成功", NO); return noErr; } AudioOutputUnitStart(_audioUnit);