转载地址:http://blog.csdn.net/shenyi0106/article/details/47004039
在Ios中,实现打开和捕获麦克风大多是用的AVCaptureSession这个组件来实现的,它可以不仅可以实现音频捕获,还可以实现视频的捕获。本文将主要实现麦克风音频的捕获和编码。
针对打开麦克风和捕获音频的代码,网上也有一些,我就简单的整理了一下:
首先,我们需要定义一个AVCaptureSession类型的变量,它是架起在麦克风设备和数据输出上的一座桥,通过它可以方便的得到麦克风的实时原始数据。
- AVCaptureSession *m_capture
同时,定义一组函数,用来打开和关闭麦克风;为了能使数据顺利的导出,你还需要实现AVCaptureAudioDataOutputSampleBufferDelegate这个协议
- -(void)open;
- -(void)close;
- -(BOOL)isOpen;
下面我们将分别实现上述参数函数,来完成数据的捕获。
- -(void)open {
- NSError *error;
- m_capture = [[AVCaptureSession alloc]init];
- AVCaptureDevice *audioDev = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
- if (audioDev == nil)
- {
- CKPrint("Couldn't create audio capture device");
- return ;
- }
-
- // create mic device
- AVCaptureDeviceInput *audioIn = [AVCaptureDeviceInput deviceInputWithDevice:audioDev error:&error];
- if (error != nil)
- {
- CKPrint("Couldn't create audio input");
- return ;
- }
-
-
- // add mic device in capture object
- if ([m_capture canAddInput:audioIn] == NO)
- {
- CKPrint("Couldn't add audio input")
- return ;
- }
- [m_capture addInput:audioIn];
- // export audio data
- AVCaptureAudioDataOutput *audioOutput = [[AVCaptureAudioDataOutput alloc] init];
- [audioOutput setSampleBufferDelegate:self queue:dispatch_get_main_queue()];
- if ([m_capture canAddOutput:audioOutput] == NO)
- {
- CKPrint("Couldn't add audio output");
- return ;
- }
- [m_capture addOutput:audioOutput];
- [audioOutput connectionWithMediaType:AVMediaTypeAudio];
- [m_capture startRunning];
- return ;
- }
- -(void)close {
- if (m_capture != nil && [m_capture isRunning])
- {
- [m_capture stopRunning];
- }
-
- return;
- }
- -(BOOL)isOpen {
- if (m_capture == nil)
- {
- return NO;
- }
-
- return [m_capture isRunning];
- }
通过上面三个函数,即可完成所有麦克风捕获的准备工作,现在我们就等着数据主动送上门了。要想数据主动送上门,我们还需要实现一个协议接口:
- - (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
- char szBuf[4096];
- int nSize = sizeof(szBuf);
-
- #if SUPPORT_AAC_ENCODER
- if ([self encoderAAC:sampleBuffer aacData:szBuf aacLen:&nSize] == YES)
- {
- [g_pViewController sendAudioData:szBuf len:nSize channel:0];
- }
- #else //#if SUPPORT_AAC_ENCODER
- AudioStreamBasicDescription outputFormat = *(CMAudioFormatDescriptionGetStreamBasicDescription(CMSampleBufferGetFormatDescription(sampleBuffer)));
- nSize = CMSampleBufferGetTotalSampleSize(sampleBuffer);
- CMBlockBufferRef databuf = CMSampleBufferGetDataBuffer(sampleBuffer);
- if (CMBlockBufferCopyDataBytes(databuf, 0, nSize, szBuf) == kCMBlockBufferNoErr)
- {
- [g_pViewController sendAudioData:szBuf len:nSize channel:outputFormat.mChannelsPerFrame];
- }
- #endif
- }
到这里,我们的工作也就差不多做完了,所捕获出来的数据是原始的PCM数据。
当然,由于PCM数据本身比较大,不利于网络传输,所以如果需要进行网络传输时,就需要对数据进行编码;Ios系统本身支持多种音频编码格式,这里我们就以AAC为例来实现一个PCM编码AAC的函数。
在Ios系统中,PCM编码AAC的例子,在网上也是一找一大片,但是大多都是不太完整的,而且相当一部分都是E文的,对于某些童鞋而言,这些都是深恶痛绝的。我这里就做做好人,把它们整理了一下,写成了一个函数,方便使用。
在编码前,需要先创建一个编码转换对象
- AVAudioConverterRef m_converter;
- #if SUPPORT_AAC_ENCODER
- -(BOOL)createAudioConvert:(CMSampleBufferRef)sampleBuffer { //根据输入样本初始化一个编码转换器
- if (m_converter != nil)
- {
- return TRUE;
- }
-
- AudioStreamBasicDescription inputFormat = *(CMAudioFormatDescriptionGetStreamBasicDescription(CMSampleBufferGetFormatDescription(sampleBuffer))); // 输入音频格式
- AudioStreamBasicDescription outputFormat; // 这里开始是输出音频格式
- memset(&outputFormat, 0, sizeof(outputFormat));
- outputFormat.mSampleRate = inputFormat.mSampleRate; // 采样率保持一致
- outputFormat.mFormatID = kAudioFormatMPEG4AAC; // AAC编码
- outputFormat.mChannelsPerFrame = 2;
- outputFormat.mFramesPerPacket = 1024; // AAC一帧是1024个字节
-
- AudioClassDescription *desc = [self getAudioClassDescriptionWithType:kAudioFormatMPEG4AAC fromManufacturer:kAppleSoftwareAudioCodecManufacturer];
- if (AudioConverterNewSpecific(&inputFormat, &outputFormat, 1, desc, &m_converter) != noErr)
- {
- CKPrint(@"AudioConverterNewSpecific failed");
- return NO;
- }
-
- return YES;
- }
- -(BOOL)encoderAAC:(CMSampleBufferRef)sampleBuffer aacData:(char*)aacData aacLen:(int*)aacLen { // 编码PCM成AAC
- if ([self createAudioConvert:sampleBuffer] != YES)
- {
- return NO;
- }
-
- CMBlockBufferRef blockBuffer = nil;
- AudioBufferList inBufferList;
- if (CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(sampleBuffer, NULL, &inBufferList, sizeof(inBufferList), NULL, NULL, 0, &blockBuffer) != noErr)
- {
- CKPrint(@"CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer failed");
- return NO;
- }
- // 初始化一个输出缓冲列表
- AudioBufferList outBufferList;
- outBufferList.mNumberBuffers = 1;
- outBufferList.mBuffers[0].mNumberChannels = 2;
- outBufferList.mBuffers[0].mDataByteSize = *aacLen; // 设置缓冲区大小
- outBufferList.mBuffers[0].mData = aacData; // 设置AAC缓冲区
- UInt32 outputDataPacketSize = 1;
- if (AudioConverterFillComplexBuffer(m_converter, inputDataProc, &inBufferList, &outputDataPacketSize, &outBufferList, NULL) != noErr)
- {
- CKPrint(@"AudioConverterFillComplexBuffer failed");
- return NO;
- }
-
- *aacLen = outBufferList.mBuffers[0].mDataByteSize; //设置编码后的AAC大小
- CFRelease(blockBuffer);
- return YES;
- }
- -(AudioClassDescription*)getAudioClassDescriptionWithType:(UInt32)type fromManufacturer:(UInt32)manufacturer { // 获得相应的编码器
- static AudioClassDescription audioDesc;
-
- UInt32 encoderSpecifier = type, size = 0;
- OSStatus status;
-
- memset(&audioDesc, 0, sizeof(audioDesc));
- status = AudioFormatGetPropertyInfo(kAudioFormatProperty_Encoders, sizeof(encoderSpecifier), &encoderSpecifier, &size);
- if (status)
- {
- return nil;
- }
-
- uint32_t count = size / sizeof(AudioClassDescription);
- AudioClassDescription descs[count];
- status = AudioFormatGetProperty(kAudioFormatProperty_Encoders, sizeof(encoderSpecifier), &encoderSpecifier, &size, descs);
- for (uint32_t i = 0; i < count; i++)
- {
- if ((type == descs[i].mSubType) && (manufacturer == descs[i].mManufacturer))
- {
- memcpy(&audioDesc, &descs[i], sizeof(audioDesc));
- break;
- }
- }
- return &audioDesc;
- }
- OSStatus inputDataProc(AudioConverterRef inConverter, UInt32 *ioNumberDataPackets, AudioBufferList *ioData,AudioStreamPacketDescription **outDataPacketDescription, voidvoid *inUserData) { //<span style="font-family: Arial, Helvetica, sans-serif;">AudioConverterFillComplexBuffer 编码过程中,会要求这个函数来填充输入数据,也就是原始PCM数据</span>
- AudioBufferList bufferList = *(AudioBufferList*)inUserData;
- ioData->mBuffers[0].mNumberChannels = 1;
- ioData->mBuffers[0].mData = bufferList.mBuffers[0].mData;
- ioData->mBuffers[0].mDataByteSize = bufferList.mBuffers[0].mDataByteSize;
- return noErr;
- }
- #endif
好了,世界是那么美好,一个函数即可所有的事情搞定了。当你需要进行AAC编码时,调用encoderAAC这个函数就可以了(在上面有完整的代码)
- char szBuf[4096];
- int nSize = sizeof(szBuf);
- if ([self encoderAAC:sampleBuffer aacData:szBuf aacLen:&nSize] == YES)
- {
- // do something
- }
-