我是流媒体应用的初学者，我从AudioBuffer创建了NSdata，我将nsdata发送到客户端（接收器）。但我不知道如何将NSdata转换为音频缓冲区。
我使用以下代码将AudioBuffer转换为NSdata（这很好用）
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
AudioStreamBasicDescription audioFormat;
memset(&audioFormat, 0, sizeof(audioFormat));
audioFormat.mSampleRate = 8000.0;
audioFormat.mFormatID = kAudioFormatiLBC;
audioFormat.mFormatFlags = kAudioFormatFlagIsBigEndian | kLinearPCMFormatFlagIsSignedInteger | kLinearPCMFormatFlagIsPacked | kAudioFormatFlagIsAlignedHigh;
audioFormat.mFramesPerPacket = 1;
audioFormat.mChannelsPerFrame = 1;
audioFormat.mBitsPerChannel = 16;
audioFormat.mBytesPerPacket = 2;
audioFormat.mReserved = 0;
audioFormat.mBytesPerFrame = audioFormat.mBytesPerPacket = audioFormat.mChannelsPerFrame* sizeof(SInt16);
AudioBufferList audioBufferList;
NSMutableData *data=[[NSMutableData alloc] init];
CMBlockBufferRef blockBuffer;
CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(sampleBuffer, NULL, &audioBufferList, sizeof(audioBufferList), NULL, NULL, 0, &blockBuffer);
for( int y=0; y<audioBufferList.mNumberBuffers; y++ )
{
AudioBuffer audioBuffer = audioBufferList.mBuffers[y];
Float32 *frame = (Float32*)audioBuffer.mData;
[data appendBytes:frame length:audioBuffer.mDataByteSize];
}
}
如果这不是正确的方法那么请帮助我....谢谢。
答案 0 :(得分：4)
您可以使用以下代码从NSData创建CMSampleBufferRef，然后使用AVAudioPlayer播放。
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection {
AudioBufferList audioBufferList;
NSMutableData *data= [NSMutableData data];
CMBlockBufferRef blockBuffer;
CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(sampleBuffer, NULL, &audioBufferList, sizeof(audioBufferList), NULL, NULL, 0, &blockBuffer);
for( int y=0; y< audioBufferList.mNumberBuffers; y++ ){
AudioBuffer audioBuffer = audioBufferList.mBuffers[y];
Float32 *frame = (Float32*)audioBuffer.mData;
[data appendBytes:frame length:audioBuffer.mDataByteSize];
}
CFRelease(blockBuffer);
CFRelease(ref);
AVAudioPlayer *player = [[AVAudioPlayer alloc] initWithData:data error:nil];
[player play];
}
答案 1 :(得分：2)
这就是我这样做的，以防其他人遇到同样的问题。您无需从AudioBufferList中获取数据，而是按原样使用它。为了再次从NSData重新创建AudioBufferList，我也需要多个样本信息，所以我在实际数据之前附加了它。
以下是如何从CMSampleBufferRef中获取数据：
AudioBufferList audioBufferList;
CMBlockBufferRef blockBuffer;
CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer(sampleBuffer, NULL, &audioBufferList, sizeof(audioBufferList), NULL, NULL, 0, &blockBuffer);
CMItemCount numSamples = CMSampleBufferGetNumSamples(sampleBuffer);
NSUInteger size = sizeof(audioBufferList);
char buffer[size + 4];
((int*)buffer)[0] = (int)numSamples;
memcpy(buffer +4, &audioBufferList, size);
//This is the Audio data.
NSData *bufferData = [NSData dataWithBytes:buffer length:size + 4];
这是您使用此数据创建AudioSampleBufferRef的方法：
const void *buffer = [bufferData bytes];
buffer = (char *)buffer;
CMSampleBufferRef sampleBuffer = NULL;
OSStatus status = -1;
/* Format Description */
AudioStreamBasicDescription audioFormat;
audioFormat.mSampleRate = 44100.00;
audioFormat.mFormatID = kAudioFormatLinearPCM;
audioFormat.mFormatFlags = 0xc;
audioFormat.mBytesPerPacket= 2;
audioFormat.mFramesPerPacket= 1;
audioFormat.mBytesPerFrame= 2;
audioFormat.mChannelsPerFrame= 1;
audioFormat.mBitsPerChannel= 16;
audioFormat.mReserved= 0;
CMFormatDescriptionRef format = NULL;
status = CMAudioFormatDescriptionCreate(kCFAllocatorDefault, &audioFormat, 0, nil, 0, nil, nil, &format);
CMFormatDescriptionRef formatdes = NULL;
status = CMFormatDescriptionCreate(NULL, kCMMediaType_Audio, 'lpcm', NULL, &formatdes);
if (status != noErr)
{
NSLog(@"Error in CMAudioFormatDescriptionCreater");
return;
}
/* Create sample Buffer */
CMSampleTimingInfo timing = {.duration= CMTimeMake(1, 44100), .presentationTimeStamp= kCMTimeZero, .decodeTimeStamp= kCMTimeInvalid};
CMItemCount framesCount = ((int*)buffer)[0];
status = CMSampleBufferCreate(kCFAllocatorDefault, nil , NO,nil,nil,format, framesCount, 1, &timing, 0, nil, &sampleBuffer);
if( status != noErr)
{
NSLog(@"Error in CMSampleBufferCreate");
return;
}
/* Copy BufferList to Sample Buffer */
AudioBufferList receivedAudioBufferList;
memcpy(&receivedAudioBufferList, buffer + 4, sizeof(receivedAudioBufferList));
status = CMSampleBufferSetDataBufferFromAudioBufferList(sampleBuffer, kCFAllocatorDefault , kCFAllocatorDefault, 0, &receivedAudioBufferList);
if (status != noErr) {
NSLog(@"Error in CMSampleBufferSetDataBufferFromAudioBufferList");
return;
}
//Use your sampleBuffer.
让我知道任何问题。
答案 2 :(得分：0)
这是我用来将音频数据（音频文件）转换为浮点表示并保存到数组中的代码。首先，我将音频数据转换为AudioBufferList，然后获取音频的浮点值数据。检查以下代码是否有帮助
-(void) PrintFloatDataFromAudioFile {
NSString * name = @"Filename"; //YOUR FILE NAME
NSString * source = [[NSBundle mainBundle] pathForResource:name ofType:@"m4a"]; // SPECIFY YOUR FILE FORMAT
const char *cString = [source cStringUsingEncoding:NSASCIIStringEncoding];
CFStringRef str = CFStringCreateWithCString(
NULL,
cString,
kCFStringEncodingMacRoman
);
CFURLRef inputFileURL = CFURLCreateWithFileSystemPath(
kCFAllocatorDefault,
str,
kCFURLPOSIXPathStyle,
false
);
ExtAudioFileRef fileRef;
ExtAudioFileOpenURL(inputFileURL, &fileRef);
AudioStreamBasicDescription audioFormat;
audioFormat.mSampleRate = 44100; // GIVE YOUR SAMPLING RATE
audioFormat.mFormatID = kAudioFormatLinearPCM;
audioFormat.mFormatFlags = kLinearPCMFormatFlagIsFloat;
audioFormat.mBitsPerChannel = sizeof(Float32) * 8;
audioFormat.mChannelsPerFrame = 1; // Mono
audioFormat.mBytesPerFrame = audioFormat.mChannelsPerFrame * sizeof(Float32); // == sizeof(Float32)
audioFormat.mFramesPerPacket = 1;
audioFormat.mBytesPerPacket = audioFormat.mFramesPerPacket * audioFormat.mBytesPerFrame; // = sizeof(Float32)
// 3) Apply audio format to the Extended Audio File
ExtAudioFileSetProperty(
fileRef,
kExtAudioFileProperty_ClientDataFormat,
sizeof (AudioStreamBasicDescription), //= audioFormat
&audioFormat);
int numSamples = 1024; //How many samples to read in at a time
UInt32 sizePerPacket = audioFormat.mBytesPerPacket; // = sizeof(Float32) = 32bytes
UInt32 packetsPerBuffer = numSamples;
UInt32 outputBufferSize = packetsPerBuffer * sizePerPacket;
// So the lvalue of outputBuffer is the memory location where we have reserved space
UInt8 *outputBuffer = (UInt8 *)malloc(sizeof(UInt8 *) * outputBufferSize);
AudioBufferList convertedData ;//= malloc(sizeof(convertedData));
convertedData.mNumberBuffers = 1; // Set this to 1 for mono
convertedData.mBuffers[0].mNumberChannels = audioFormat.mChannelsPerFrame; //also = 1
convertedData.mBuffers[0].mDataByteSize = outputBufferSize;
convertedData.mBuffers[0].mData = outputBuffer; //
UInt32 frameCount = numSamples;
float *samplesAsCArray;
int j =0;
double floatDataArray[882000] ; // SPECIFY YOUR DATA LIMIT MINE WAS 882000 , SHOULD BE EQUAL TO OR MORE THAN DATA LIMIT
while (frameCount > 0) {
ExtAudioFileRead(
fileRef,
&frameCount,
&convertedData
);
if (frameCount > 0) {
AudioBuffer audioBuffer = convertedData.mBuffers[0];
samplesAsCArray = (float *)audioBuffer.mData; // CAST YOUR mData INTO FLOAT
for (int i =0; i<1024 /*numSamples */; i++) { //YOU CAN PUT numSamples INTEAD OF 1024
floatDataArray[j] = (double)samplesAsCArray[i] ; //PUT YOUR DATA INTO FLOAT ARRAY
printf("\n%f",floatDataArray[j]); //PRINT YOUR ARRAY'S DATA IN FLOAT FORM RANGING -1 TO +1
j++;
}
}
}}
答案 3 :(得分：0)
我使用以下代码片段将NSData（在我的800字节数据包的情况下，但可以说是任何大小）转换为AudioBufferList：
-(AudioBufferList *) getBufferListFromData: (NSData *) data
{
if (data.length > 0)
{
NSUInteger len = [data length];
//I guess you can use Byte*, void* or Float32*. I am not sure if that makes any difference.
Byte * byteData = (Byte*) malloc (len);
memcpy (byteData, [data bytes], len);
if (byteData)
{
AudioBufferList * theDataBuffer =(AudioBufferList*)malloc(sizeof(AudioBufferList) * 1);
theDataBuffer->mNumberBuffers = 1;
theDataBuffer->mBuffers[0].mDataByteSize = len;
theDataBuffer->mBuffers[0].mNumberChannels = 1;
theDataBuffer->mBuffers[0].mData = byteData;
// Read the data into an AudioBufferList
return theDataBuffer;
}
}
return nil;
}