我有一个IPCamer,需要使用自定义库进行连接和通信。我已经处理好了视频,但我还想给用户提供听取摄像机录制的音频的选项。
我以字节流的形式接收音频(音频是PCM u-law)。
由于我没有从文件中读取数据或连接到URL,我认为我必须使用像AudioUnits或openAL这样的东西来播放音频。
我尝试根据我在网上找到的示例使用AudioUnits进行实现,这是我目前的进展:
我以字节流的形式接收音频(音频是PCM u-law)。
由于我没有从文件中读取数据或连接到URL,我认为我必须使用像AudioUnits或openAL这样的东西来播放音频。
我尝试根据我在网上找到的示例使用AudioUnits进行实现,这是我目前的进展:
-(void) audioThread
{
char buffer[1024];
int size = 0;
boolean audioConfigured = false;
AudioComponentInstance audioUnit;
while (running) {
getAudioData(buffer,size); //fill buffer with my audio
int16_t* tempChar = (int16_t *)calloc(ret, sizeof(int16_t));
for (int i = 0; i < ret; i++) {
tempChar[i] = MuLaw_Decode(buf[i]);
}
uint8_t *data = NULL;
data = malloc(size);
data = memcpy(data, &tempChar, size);
CMBlockBufferRef blockBuffer = NULL;
OSStatus status = CMBlockBufferCreateWithMemoryBlock(NULL, data,
size,
kCFAllocatorNull, NULL,
0,
size,
0, &blockBuffer);
CMSampleBufferRef sampleBuffer = NULL;
// now I create my samplebuffer from the block buffer
if(status == noErr)
{
const size_t sampleSize = size;
status = CMSampleBufferCreate(kCFAllocatorDefault,
blockBuffer, true, NULL, NULL,
formatDesc, 1, 0, NULL, 1,
&sampleSize, &sampleBuffer);
}
AudioStreamBasicDescription audioBasic;
audioBasic.mBitsPerChannel = 16;
audioBasic.mBytesPerPacket = 2;
audioBasic.mBytesPerFrame = 2;
audioBasic.mChannelsPerFrame = 1;
audioBasic.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
audioBasic.mFormatID = kAudioFormatLinearPCM;
audioBasic.mFramesPerPacket = 1;
audioBasic.mSampleRate = 48000;
audioBasic.mReserved = 0;
if(!audioConfigured)
{
//initialize the circular buffer
if(instance.decodingBuffer == NULL)
instance.decodingBuffer = malloc(sizeof(TPCircularBuffer));
if(!TPCircularBufferInit(instance.decodingBuffer, 1024))
continue;
AudioComponentDescription componentDescription;
componentDescription.componentType = kAudioUnitType_Output;
componentDescription.componentSubType = kAudioUnitSubType_RemoteIO;
componentDescription.componentManufacturer = kAudioUnitManufacturer_Apple;
componentDescription.componentFlags = 0;
componentDescription.componentFlagsMask = 0;
AudioComponent component = AudioComponentFindNext(NULL, &componentDescription);
if(AudioComponentInstanceNew(component, &audioUnit) != noErr) {
NSLog(@"Failed to initialize the AudioComponent");
continue;
}
//enable IO for playback
UInt32 flag = 1;
if(AudioUnitSetProperty(audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Output, 0, &flag, sizeof(flag)) != noErr) {
NSLog(@"Failed to enable IO for playback");
continue;
}
// set the format for the outputstream
if(AudioUnitSetProperty(audioUnit, kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Output, 1, &audioBasic, sizeof(audioBasic)) != noErr) {
NSLog(@"Failed to set the format for the outputstream");
continue;
}
// set output callback
AURenderCallbackStruct callbackStruct;
callbackStruct.inputProc = playbackCallback;
callbackStruct.inputProcRefCon = (__bridge void*) self;
if(AudioUnitSetProperty(audioUnit, kAudioUnitProperty_SetRenderCallback, kAudioUnitScope_Global, 0, &callbackStruct, sizeof(callbackStruct))!= noErr) {
NSLog(@"Failed to Set output callback");
continue;
}
// Disable buffer allocation for the recorder (optional - do this if we want to pass in our own)
flag = 0;
status = AudioUnitSetProperty(audioUnit, kAudioUnitProperty_ShouldAllocateBuffer, kAudioUnitScope_Output, 1, &flag, sizeof(flag));
if(AudioUnitInitialize(audioUnit) != noErr) {
NSLog(@"Failed to initialize audioUnits");
}
if(AudioOutputUnitStart(audioUnit)!= noErr) {
NSLog(@"[thread_ReceiveAudio] Failed to start audio");
}
audioConfigured = true;
}
AudioBufferList bufferList ;
if (sampleBuffer!=NULL) {
CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(sampleBuffer, NULL, &bufferList, sizeof(bufferList), NULL, NULL, kCMSampleBufferFlag_AudioBufferList_Assure16ByteAlignment, &blockBuffer);
UInt64 size = CMSampleBufferGetTotalSampleSize(sampleBuffer);
// Put audio into circular buffer
TPCircularBufferProduceBytes(self.decodingBuffer, bufferList.mBuffers[0].mData, size);
//TPCircularBufferCopyAudioBufferList(self.decodingBuffer, &bufferList, NULL, kTPCircularBufferCopyAll, NULL);
CFRelease(sampleBuffer);
CFRelease(blockBuffer);
}
}
//stop playing audio
if(audioConfigured){
if(AudioOutputUnitStop(audioUnit)!= noErr) {
NSLog(@"[thread_ReceiveAudio] Failed to stop audio");
}
else{
//clean up audio
AudioComponentInstanceDispose(audioUnit);
}
}
}
int16_t MuLaw_Decode(int8_t number)
{
const uint16_t MULAW_BIAS = 33;
uint8_t sign = 0, position = 0;
int16_t decoded = 0;
number = ~number;
if (number & 0x80)
{
number &= ~(1 << 7);
sign = -1;
}
position = ((number & 0xF0) >> 4) + 5;
decoded = ((1 << position) | ((number & 0x0F) << (position - 4))
| (1 << (position - 5))) - MULAW_BIAS;
return (sign == 0) ? (decoded) : (-(decoded));
}
static OSStatus playbackCallback(void *inRefCon,
AudioUnitRenderActionFlags *ioActionFlags,
const AudioTimeStamp *inTimeStamp,
UInt32 inBusNumber,
UInt32 inNumberFrames,
AudioBufferList *ioData) {
int bytesToCopy = ioData->mBuffers[0].mDataByteSize;
SInt16 *targetBuffer = (SInt16*)ioData->mBuffers[0].mData;
int32_t availableBytes;
SInt16 *buffer = TPCircularBufferTail(instance.decodingBuffer, &availableBytes);
int sampleCount = MIN(bytesToCopy, availableBytes);
memcpy(targetBuffer, buffer, MIN(bytesToCopy, availableBytes));
TPCircularBufferConsume(self.decodingBuffer, sampleCount);
return noErr;
}
以上代码没有产生任何错误,但不会播放任何声音。我以为可以在recordCallback中通过bufferList设置音频,但它从未被调用。
所以我的问题是:如何在iOS上从字节流播放音频?