概述
本文展示如何将两个音频文件数据读取到内存，作为MixerAudioUnit的两路输入，混合后将MixerAudioUnit的数据输出作为Remot I/O AudioUnit的输入，最后启动AudioGraph播放。
另外还将讲解如何调节两路音频的输入的音量，以及调节混合后音频的音量
着重讲解下，链路拉取音频数据时，如何给MixerAudioUnit填充数据，这个很多文章没有讲清楚这里为啥这么填充，填充后是什么效果，怎么填充可以播放整个文件，怎样填充可以循环播放，或者填充时有哪些注意点，可能会导致的音频出现鞭炮声，播放不出等等原因
1.将本地两个音频文件读取到内存
将本地文件读取到ExtAudioFileRef里面
CFURLRef sourceURL[2];// 这个是加载的文件URL
NSString *sourceA = [[NSBundle mainBundle] pathForResource:@"GuitarMonoSTP" ofType:@"aif"];
NSString *sourceB = [[NSBundle mainBundle] pathForResource:@"DrumsMonoSTP" ofType:@"aif"];
sourceURL[0] = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, (CFStringRef)sourceA, kCFURLPOSIXPathStyle, false);
sourceURL[1] = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, (CFStringRef)sourceB, kCFURLPOSIXPathStyle, false);
ExtAudioFileRef xafref = 0;
OSStatus result = ExtAudioFileOpenURL(sourceURL[i], &xafref);// 打开URL到文件xafref
从ExtAudioFileRef读取设定的音频格式的数据
// 设定的输出格式：音频格式为PCM格式，采样率44100， 采样位数4个字节AVAudioPCMFormatFloat32，通道数1，交互存储（通道数为1的时候，交互存储有意义吗？我这里认为是没有意义的，填写YES或者NO都可以）
AVAudioFormat *clientFormat = [[AVAudioFormat alloc] initWithCommonFormat:AVAudioPCMFormatFloat32
sampleRate:kGraphSampleRate
channels:1
interleaved:YES];
// 获取文件的数据格式fileFormat
// get the file data format, this represents the file's actual data format
AudioStreamBasicDescription fileFormat;
UInt32 propSize = sizeof(fileFormat);
OSStatus result = ExtAudioFileGetProperty(xafref, kExtAudioFileProperty_FileDataFormat, &propSize, &fileFormat);
// get the file's length in sample frames 获取文件的长度， 以帧数计的长度，即这个文件有多少帧
UInt64 numFrames = 0;
propSize = sizeof(numFrames);
result = ExtAudioFileGetProperty(xafref, kExtAudioFileProperty_FileLengthFrames, &propSize, &numFrames);
// 设置文件的输出格式
propSize = sizeof(AudioStreamBasicDescription);
result = ExtAudioFileSetProperty(xafref, kExtAudioFileProperty_ClientDataFormat, propSize, clientFormat.streamDescription);
// used to account for any sample rate conversion 采样率比
double rateRatio = kGraphSampleRate / fileFormat.mSampleRate;
numFrames = (numFrames * rateRatio); // account for any sample rate conversion 计算输出后的长度，以帧数计
// set up our buffer
mSoundBuffer[i].numFrames = (UInt32)numFrames;
mSoundBuffer[i].asbd = *(clientFormat.streamDescription);
UInt32 samples = (UInt32)numFrames * mSoundBuffer[i].asbd.mChannelsPerFrame;
mSoundBuffer[i].data = (Float32 *)calloc(samples, sizeof(Float32));
mSoundBuffer[i].sampleNum = 0;
// set up a AudioBufferList to read data into
AudioBufferList bufList;
bufList.mNumberBuffers = 1;
bufList.mBuffers[0].mNumberChannels = 1;
bufList.mBuffers[0].mData = mSoundBuffer[i].data;
bufList.mBuffers[0].mDataByteSize = samples * sizeof(Float32);
// perform a synchronous sequential read of the audio data out of the file into our allocated data buffer
UInt32 numPackets = (UInt32)numFrames;
result = ExtAudioFileRead(xafref, &numPackets, &bufList);
2.建立AUGraph，将两个文件的音频数据作为Mixer AudioUnit的输入
image.png
首先有几个点需要说下，Mixer Unit的InputScope有多个Element， OutputScope有1个Element，和Remote I/O Unit有些不一样，Remote I//O Unit 有2个Element，但是每个Element有各自的InputScope和OutputScope
建立Augraph就是建立这个连接
2.1 建立AUGraph
1.生成Mixer AudioUnit 和Remote I/O AudioUnit
AUNode outputNode;
AUNode mixerNode;
// this is the format for the graph
mAudioFormat = [[AVAudioFormat alloc] initWithCommonFormat:AVAudioPCMFormatFloat32
sampleRate:kGraphSampleRate
channels:2
interleaved:NO];
// create a new AUGraph
result = NewAUGraph(&mGraph);
// output unit
CAComponentDescription output_desc(kAudioUnitType_Output, kAudioUnitSubType_RemoteIO, kAudioUnitManufacturer_Apple);
CAShowComponentDescription(&output_desc);
// multichannel mixer unit
/**
多通道MixerUnit 的InputScope 可以设置有多个Element，outputScope有1个Element
*/
CAComponentDescription mixer_desc(kAudioUnitType_Mixer, kAudioUnitSubType_MultiChannelMixer, kAudioUnitManufacturer_Apple);
CAShowComponentDescription(&mixer_desc);
printf("new nodes\n");
// create a node in the graph that is an AudioUnit, using the supplied AudioComponentDescription to find and open that unit
result = AUGraphAddNode(mGraph, &output_desc, &outputNode);
if (result) { printf("AUGraphNewNode 1 result %ld %4.4s\n", (long)result, (char*)&result); return; }
result = AUGraphAddNode(mGraph, &mixer_desc, &mixerNode );
if (result) { printf("AUGraphNewNode 2 result %ld %4.4s\n", (long)result, (char*)&result); return; }
2.2 连接mixer unit 和 remote i/o unit
这里是将Mixer Unit的0 Element 输出作为Remote Unit的0Element的输入， Remote I/O Unit的默认是0element的输出作为1Element的输入，1Element的输出是扬声器
// connect a node's output to a node's input
result = AUGraphConnectNodeInput(mGraph, mixerNode, 0, outputNode, 0);
2.3 将音频文件的数据设置为Mixer unit的输入
for (int i = 0; i < numbuses; ++i) {
// setup render callback struct
AURenderCallbackStruct rcbs;
rcbs.inputProc = &renderInput;
rcbs.inputProcRefCon = mSoundBuffer;
printf("set kAudioUnitProperty_SetRenderCallback for mixer input bus %d\n", i);
// Set a callback for the specified node's specified input
/**
设置InputScope的第i个 Element的输入回调
*/
result = AUGraphSetNodeInputCallback(mGraph, mixerNode, i, &rcbs);
// equivalent to AudioUnitSetProperty(mMixer, kAudioUnitProperty_SetRenderCallback, kAudioUnitScope_Input, i, &rcbs, sizeof(rcbs));
if (result) { printf("AUGraphSetNodeInputCallback result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
// set input stream format to what we want
printf("set mixer input kAudioUnitProperty_StreamFormat for bus %d\n", i);
// 设置InputScope的第i个 Element的音频格式
result = AudioUnitSetProperty(mMixer, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, i, mAudioFormat.streamDescription, sizeof(AudioStreamBasicDescription));
if (result) { printf("AudioUnitSetProperty result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
}
2.4 设置Mixer Unit的输出格式
// 设置OutputScope的第0个 Element的音频格式，一般就只有1个Element
result = AudioUnitSetProperty(mMixer, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, mAudioFormat.streamDescription, sizeof(AudioStreamBasicDescription));
2.5 设置Remote Unit的输出格式
result = AudioUnitSetProperty(mOutput, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, mAudioFormat.streamDescription, sizeof(AudioStreamBasicDescription));
3.启动AUGraph
建立AUGraph之后，就可以启动工作了，一旦启动，需要数据时，就会触发我们前面设置的inputCallback,需要在这里对其填充数据
3.1 启动
result = AUGraphInitialize(mGraph);
OSStatus result = AUGraphStart(mGraph);
3.2 音频拉取数据回调时填充数据
因为我们设置了数据输出格式是2通道的非交叉类型，即LLLLRRRR，而不是LRLRLR，需要给ioData[0]填充左声道数据，给ioData【1】填充右声道数据，这个填充可以任意填你想要的效果，比如我左声道就第一个音频的数据，右声道填第二个音频的数据，这样播放出来的效果就是左扬声器只有第一个音频的声音，右扬声器只有第二个音频的声音；或者我左右声道填2个数据，这样左右扬声器播放出来的声音是混音。
这个拉取音频数据回调函数，是每次需要数据时都会调用，如果这里耗时，则会导致出现声音数据获取不及时，出现卡顿，一会有声音，一会没有，听起来像放鞭炮一样，或者没有声音播放出来
循环播放原理很简单：就是通过记录拉取的数是多少帧，给回调函数填充数据时，当拉取道最后一帧时，重新设置sample=0,从头开始拉取，这样，就实现了循环播放
static OSStatus renderInput(void *inRefCon, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData)
{
/**
AURenderCallbackStruct rcbs;
rcbs.inputProc = &renderInput;
rcbs.inputProcRefCon = mSoundBuffer;
当时设置的inRefCon为mSoundBuffer，其是一个数组 SoundBuffer mSoundBuffer[MAXBUFS]; 或者说是SoundBuffer的一个指针SoundBufferPtr
*/
SoundBufferPtr sndbuf = (SoundBufferPtr)inRefCon;
UInt32 sample = sndbuf[inBusNumber].sampleNum; // frame number to start from
UInt32 bufSamples = sndbuf[inBusNumber].numFrames; // total number of frames in the sound buffer 输入的文件总的帧数
Float32 *in = sndbuf[inBusNumber].data; // audio data buffer
// mixerUnit设置输出为2通道
Float32 *outA = (Float32 *)ioData->mBuffers[0].mData; // output audio buffer for L channel
Float32 *outB = (Float32 *)ioData->mBuffers[1].mData; // output audio buffer for R channel
// for demonstration purposes we've configured 2 stereo input busses for the mixer unit
// but only provide a single channel of data from each input bus when asked and silence for the other channel
// alternating as appropriate when asked to render bus 0 or bus 1's input // 交替渲染 bus 0 or bus 1
/**
mixerUnit的输出格式，不交错，所以(Float32 *)ioData->mBuffers[0].mData; // output audio buffer for L channel
(Float32 *)ioData->mBuffers[1].mData; // output audio buffer for R channel
mAudioFormat = [[AVAudioFormat alloc] initWithCommonFormat:AVAudioPCMFormatFloat32
sampleRate:kGraphSampleRate
channels:2
interleaved:NO];
*/
for (UInt32 i = 0; i < inNumberFrames; ++i) {
// 这种方式是两个通道交替渲染bus0，和bus1的声音
if (1 == inBusNumber) {
outA[i] = 0;
outB[i] = in[sample++];
} else {
outA[i] = in[sample++];
outB[i] = 0;
}
// // 这种方式是两个通道把各自把bus0和bus1的一起渲染
// if (1 == inBusNumber) {//
// outB[i] = in[sample++];
// outA[i] = outB[i] ;
// } else {
// outA[i] = in[sample++];
// outB[i] = outA[i];
// }
// 控制进行循环播放的
if (sample > bufSamples) {
// start over from the beginning of the data, our audio simply loops
printf("looping data for bus %d after %ld source frames rendered\n", (unsigned int)inBusNumber, (long)sample-1);
sample = 0;
}
}
// 记录播放的位置，下一次拉取音频数据时，就能往后拉取，通过这个控制拉取不同位置的数据，以及控制循环播放
sndbuf[inBusNumber].sampleNum = sample; // keep track of where we are in the source data buffer
// 加入下面的打印等耗时操作，就会出现鞭炮声（即某一时刻获取声音数据时延迟卡顿导致播放不了）
// printf("bus %d sample %d\n", (unsigned int)inBusNumber, (unsigned int)sample);
// for (int i = 0; i < 10; i++) {
// NSObject *obj = [NSObject new];
//
// NSLog(@"bus %@ \n", obj);
// }
return noErr;
}
4.调节音量
调节音量直接设置AudioUnit的属性即可
给两路音频控制其输入音量大小
// sets the input volume for a specific bus
- (void)setInputVolume:(UInt32)inputNum value:(AudioUnitParameterValue)value
{
OSStatus result = AudioUnitSetParameter(mMixer, kMultiChannelMixerParam_Volume, kAudioUnitScope_Input, inputNum, value, 0);
if (result) { printf("AudioUnitSetParameter kMultiChannelMixerParam_Volume Input result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
}
给混合后的音频设置其输出音量大小
// sets the overall mixer output volume
- (void)setOutputVolume:(AudioUnitParameterValue)value
{
OSStatus result = AudioUnitSetParameter(mMixer, kMultiChannelMixerParam_Volume, kAudioUnitScope_Output, 0, value, 0);
if (result) { printf("AudioUnitSetParameter kMultiChannelMixerParam_Volume Output result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
}
5.下面放的是Demo里关键代码
demo其实是苹果官方的demo，我在里面加了些注释而已
MultichannelMixerController.h
/*
Copyright (C) 2015 Apple Inc. All Rights Reserved.
See LICENSE.txt for this sample’s licensing information
Abstract:
The Controller Class for the AUGraph.
*/
#import <AudioToolbox/AudioToolbox.h>
#import <AudioUnit/AudioUnit.h>
#import <AVFoundation/AVAudioFormat.h>
#import "CAComponentDescription.h"
#define MAXBUFS 2
#define NUMFILES 2
typedef struct {
AudioStreamBasicDescription asbd;
Float32 *data;
UInt32 numFrames;
UInt32 sampleNum;
} SoundBuffer, *SoundBufferPtr;
@interface MultichannelMixerController : NSObject
{
CFURLRef sourceURL[2];
AVAudioFormat *mAudioFormat;
AUGraph mGraph;
AudioUnit mMixer;
AudioUnit mOutput;
SoundBuffer mSoundBuffer[MAXBUFS];
Boolean isPlaying;
}
@property (readonly, nonatomic) Boolean isPlaying;
- (void)initializeAUGraph;
- (void)enableInput:(UInt32)inputNum isOn:(AudioUnitParameterValue)isONValue;
- (void)setInputVolume:(UInt32)inputNum value:(AudioUnitParameterValue)value;
- (void)setOutputVolume:(AudioUnitParameterValue)value;
- (void)startAUGraph;
- (void)stopAUGraph;
@end
MultichannelMixerController.m
/*
Copyright (C) 2015 Apple Inc. All Rights Reserved.
See LICENSE.txt for this sample’s licensing information
Abstract:
The Controller Class for the AUGraph.
*/
#import "MultiChannelMixerController.h"
const Float64 kGraphSampleRate = 44100.0; // 48000.0 optional tests
#pragma mark- RenderProc
/**
这个方法是专门为音频拉取数据调用时候填充数据
*/
// audio render procedure, don't allocate memory, don't take any locks, don't waste time, printf statements for debugging only may adversly affect render you have been warned
static OSStatus renderInput(void *inRefCon, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData)
{
/**
AURenderCallbackStruct rcbs;
rcbs.inputProc = &renderInput;
rcbs.inputProcRefCon = mSoundBuffer;
当时设置的inRefCon为mSoundBuffer，其是一个数组 SoundBuffer mSoundBuffer[MAXBUFS]; 或者说是SoundBuffer的一个指针SoundBufferPtr
*/
SoundBufferPtr sndbuf = (SoundBufferPtr)inRefCon;
UInt32 sample = sndbuf[inBusNumber].sampleNum; // frame number to start from
UInt32 bufSamples = sndbuf[inBusNumber].numFrames; // total number of frames in the sound buffer 输入的文件总的帧数
Float32 *in = sndbuf[inBusNumber].data; // audio data buffer
// mixerUnit设置输出为2通道
Float32 *outA = (Float32 *)ioData->mBuffers[0].mData; // output audio buffer for L channel
Float32 *outB = (Float32 *)ioData->mBuffers[1].mData; // output audio buffer for R channel
// for demonstration purposes we've configured 2 stereo input busses for the mixer unit
// but only provide a single channel of data from each input bus when asked and silence for the other channel
// alternating as appropriate when asked to render bus 0 or bus 1's input // 交替渲染 bus 0 or bus 1
/**
mixerUnit的输出格式，不交错，所以(Float32 *)ioData->mBuffers[0].mData; // output audio buffer for L channel
(Float32 *)ioData->mBuffers[1].mData; // output audio buffer for R channel
mAudioFormat = [[AVAudioFormat alloc] initWithCommonFormat:AVAudioPCMFormatFloat32
sampleRate:kGraphSampleRate
channels:2
interleaved:NO];
*/
for (UInt32 i = 0; i < inNumberFrames; ++i) {
// 这种方式是两个通道交替渲染bus0，和bus1的声音
if (1 == inBusNumber) {
outA[i] = 0;
outB[i] = in[sample++];
} else {
outA[i] = in[sample++];
outB[i] = 0;
}
// // 这种方式是两个通道把各自把bus0和bus1的一起渲染
// if (1 == inBusNumber) {//
// outB[i] = in[sample++];
// outA[i] = outB[i] ;
// } else {
// outA[i] = in[sample++];
// outB[i] = outA[i];
// }
// 控制进行循环播放的
if (sample > bufSamples) {
// start over from the beginning of the data, our audio simply loops
printf("looping data for bus %d after %ld source frames rendered\n", (unsigned int)inBusNumber, (long)sample-1);
sample = 0;
}
}
// 记录播放的位置
sndbuf[inBusNumber].sampleNum = sample; // keep track of where we are in the source data buffer
// 加入下面的打印等耗时操作，就会出现鞭炮声（即某一时刻获取声音数据时延迟卡顿导致播放不了）
// printf("bus %d sample %d\n", (unsigned int)inBusNumber, (unsigned int)sample);
// for (int i = 0; i < 10; i++) {
// NSObject *obj = [NSObject new];
//
// NSLog(@"bus %@ \n", obj);
// }
return noErr;
}
#pragma mark- MultichannelMixerController
@interface MultichannelMixerController (hidden)
- (void)loadFiles;
@end
@implementation MultichannelMixerController
@synthesize isPlaying;
- (void)dealloc
{
printf("MultichannelMixerController dealloc\n");
DisposeAUGraph(mGraph);
free(mSoundBuffer[0].data);
free(mSoundBuffer[1].data);
CFRelease(sourceURL[0]);
CFRelease(sourceURL[1]);
[mAudioFormat release];
[super dealloc];
}
- (void)awakeFromNib
{
printf("awakeFromNib\n");
isPlaying = false;
// clear the mSoundBuffer struct
memset(&mSoundBuffer, 0, sizeof(mSoundBuffer));
// create the URLs we'll use for source A and B
NSString *sourceA = [[NSBundle mainBundle] pathForResource:@"GuitarMonoSTP" ofType:@"aif"];
NSString *sourceB = [[NSBundle mainBundle] pathForResource:@"DrumsMonoSTP" ofType:@"aif"];
sourceURL[0] = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, (CFStringRef)sourceA, kCFURLPOSIXPathStyle, false);
sourceURL[1] = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, (CFStringRef)sourceB, kCFURLPOSIXPathStyle, false);
}
- (void)initializeAUGraph
{
printf("initialize\n");
AUNode outputNode;
AUNode mixerNode;
// this is the format for the graph
mAudioFormat = [[AVAudioFormat alloc] initWithCommonFormat:AVAudioPCMFormatFloat32
sampleRate:kGraphSampleRate
channels:2
interleaved:NO];
OSStatus result = noErr;
// load up the audio data
[self performSelectorInBackground:@selector(loadFiles) withObject:nil];
// create a new AUGraph
result = NewAUGraph(&mGraph);
if (result) { printf("NewAUGraph result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
// create two AudioComponentDescriptions for the AUs we want in the graph
// output unit
CAComponentDescription output_desc(kAudioUnitType_Output, kAudioUnitSubType_RemoteIO, kAudioUnitManufacturer_Apple);
CAShowComponentDescription(&output_desc);
// multichannel mixer unit
/**
多通道MixerUnit 的InputScope 可以设置有多个Element，outputScope有1个Element
*/
CAComponentDescription mixer_desc(kAudioUnitType_Mixer, kAudioUnitSubType_MultiChannelMixer, kAudioUnitManufacturer_Apple);
CAShowComponentDescription(&mixer_desc);
printf("new nodes\n");
// create a node in the graph that is an AudioUnit, using the supplied AudioComponentDescription to find and open that unit
result = AUGraphAddNode(mGraph, &output_desc, &outputNode);
if (result) { printf("AUGraphNewNode 1 result %ld %4.4s\n", (long)result, (char*)&result); return; }
result = AUGraphAddNode(mGraph, &mixer_desc, &mixerNode );
if (result) { printf("AUGraphNewNode 2 result %ld %4.4s\n", (long)result, (char*)&result); return; }
// connect a node's output to a node's input
result = AUGraphConnectNodeInput(mGraph, mixerNode, 0, outputNode, 0);
if (result) { printf("AUGraphConnectNodeInput result %ld %4.4s\n", (long)result, (char*)&result); return; }
// open the graph AudioUnits are open but not initialized (no resource allocation occurs here)
result = AUGraphOpen(mGraph);
if (result) { printf("AUGraphOpen result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
result = AUGraphNodeInfo(mGraph, mixerNode, NULL, &mMixer);
if (result) { printf("AUGraphNodeInfo result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
result = AUGraphNodeInfo(mGraph, outputNode, NULL, &mOutput);
if (result) { printf("AUGraphNodeInfo result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
// set bus count
UInt32 numbuses = 2;
printf("set input bus count %u\n", (unsigned int)numbuses);
/**
多通道MixerUnit 的InputScope 可以设置有多个Element，outputScope有1个Element
*/
result = AudioUnitSetProperty(mMixer, kAudioUnitProperty_ElementCount, kAudioUnitScope_Input, 0, &numbuses, sizeof(numbuses));
if (result) { printf("AudioUnitSetProperty result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
for (int i = 0; i < numbuses; ++i) {
// setup render callback struct
AURenderCallbackStruct rcbs;
rcbs.inputProc = &renderInput;
rcbs.inputProcRefCon = mSoundBuffer;
printf("set kAudioUnitProperty_SetRenderCallback for mixer input bus %d\n", i);
// Set a callback for the specified node's specified input
/**
设置InputScope的第i个 Element的输入回调
*/
result = AUGraphSetNodeInputCallback(mGraph, mixerNode, i, &rcbs);
// equivalent to AudioUnitSetProperty(mMixer, kAudioUnitProperty_SetRenderCallback, kAudioUnitScope_Input, i, &rcbs, sizeof(rcbs));
if (result) { printf("AUGraphSetNodeInputCallback result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
// set input stream format to what we want
printf("set mixer input kAudioUnitProperty_StreamFormat for bus %d\n", i);
// 设置InputScope的第i个 Element的音频格式
result = AudioUnitSetProperty(mMixer, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, i, mAudioFormat.streamDescription, sizeof(AudioStreamBasicDescription));
if (result) { printf("AudioUnitSetProperty result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
}
// set output stream format to what we want
printf("set output kAudioUnitProperty_StreamFormat\n");
// 设置OutputScope的第0个 Element的音频格式，一般就只有1个Element
result = AudioUnitSetProperty(mMixer, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 0, mAudioFormat.streamDescription, sizeof(AudioStreamBasicDescription));
if (result) { printf("AudioUnitSetProperty result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
// 设置Remote IO Unit 的OutputScope的第1个 Element的音频格式，有2个Element，第0个Element 0 的系统默认输入为麦克风，可以配置第0个Element的输出为第1个Element的输入，第1个Element的输出为扬声器，这里是设置第1个Element的输出格式
result = AudioUnitSetProperty(mOutput, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, 1, mAudioFormat.streamDescription, sizeof(AudioStreamBasicDescription));
if (result) { printf("AudioUnitSetProperty result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
printf("AUGraphInitialize\n");
// now that we've set everything up we can initialize the graph, this will also validate the connections
result = AUGraphInitialize(mGraph);
if (result) { printf("AUGraphInitialize result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
CAShow(mGraph);
}
// load up audio data from the demo files into mSoundBuffer.data used in the render proc
- (void)loadFiles
{
// 输出格式：音频格式为PCM格式，采样率44100， 采样位数4个字节AVAudioPCMFormatFloat32，通道数1，交互存储（通道数为1的时候，交互存储有意义吗？）
AVAudioFormat *clientFormat = [[AVAudioFormat alloc] initWithCommonFormat:AVAudioPCMFormatFloat32
sampleRate:kGraphSampleRate
channels:1
interleaved:YES];
for (int i = 0; i < NUMFILES && i < MAXBUFS; i++) {
printf("loadFiles, %d\n", i);
ExtAudioFileRef xafref = 0;
// open one of the two source files 打开文件xafref
OSStatus result = ExtAudioFileOpenURL(sourceURL[i], &xafref);
if (result || !xafref) { printf("ExtAudioFileOpenURL result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); break; }
// get the file data format, this represents the file's actual data format
AudioStreamBasicDescription fileFormat;
UInt32 propSize = sizeof(fileFormat);
// 获取文件的数据格式fileFormat
result = ExtAudioFileGetProperty(xafref, kExtAudioFileProperty_FileDataFormat, &propSize, &fileFormat);
if (result) { printf("ExtAudioFileGetProperty kExtAudioFileProperty_FileDataFormat result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); break; }
// set the client format - this is the format we want back from ExtAudioFile and corresponds to the format
// we will be providing to the input callback of the mixer, therefore the data type must be the same
// used to account for any sample rate conversion 采样率比
double rateRatio = kGraphSampleRate / fileFormat.mSampleRate;
// 设置文件的输出格式
propSize = sizeof(AudioStreamBasicDescription);
result = ExtAudioFileSetProperty(xafref, kExtAudioFileProperty_ClientDataFormat, propSize, clientFormat.streamDescription);
if (result) { printf("ExtAudioFileSetProperty kExtAudioFileProperty_ClientDataFormat %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); break; }
// get the file's length in sample frames 获取文件的长度， 以帧数计的长度
UInt64 numFrames = 0;
propSize = sizeof(numFrames);
result = ExtAudioFileGetProperty(xafref, kExtAudioFileProperty_FileLengthFrames, &propSize, &numFrames);
if (result) { printf("ExtAudioFileGetProperty kExtAudioFileProperty_FileLengthFrames result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); break; }
printf("File %d, Number of Sample Frames: %u\n", i, (unsigned int)numFrames);
numFrames = (numFrames * rateRatio); // account for any sample rate conversion 计算输出后的长度，以帧数计
printf("File %d, Number of Sample Frames after rate conversion (if any): %u\n", i, (unsigned int)numFrames);
// set up our buffer
mSoundBuffer[i].numFrames = (UInt32)numFrames;
mSoundBuffer[i].asbd = *(clientFormat.streamDescription);
UInt32 samples = (UInt32)numFrames * mSoundBuffer[i].asbd.mChannelsPerFrame;
mSoundBuffer[i].data = (Float32 *)calloc(samples, sizeof(Float32));
mSoundBuffer[i].sampleNum = 0;
// set up a AudioBufferList to read data into
AudioBufferList bufList;
bufList.mNumberBuffers = 1;//几个数据数组
bufList.mBuffers[0].mNumberChannels = 1;// 通道数，输入音频的通道数都是1的
bufList.mBuffers[0].mData = mSoundBuffer[i].data;// 数据地址
bufList.mBuffers[0].mDataByteSize = samples * sizeof(Float32);// 数据大小
// perform a synchronous sequential read of the audio data out of the file into our allocated data buffer
UInt32 numPackets = (UInt32)numFrames;
result = ExtAudioFileRead(xafref, &numPackets, &bufList);
if (result) {
printf("ExtAudioFileRead result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result);
free(mSoundBuffer[i].data);
mSoundBuffer[i].data = 0;
}
// close the file and dispose the ExtAudioFileRef
ExtAudioFileDispose(xafref);
}
[clientFormat release];
}
#pragma mark-
// enable or disables a specific bus
- (void)enableInput:(UInt32)inputNum isOn:(AudioUnitParameterValue)isONValue
{
printf("BUS %d isON %f\n", (unsigned int)inputNum, isONValue);
OSStatus result = AudioUnitSetParameter(mMixer, kMultiChannelMixerParam_Enable, kAudioUnitScope_Input, inputNum, isONValue, 0);
if (result) { printf("AudioUnitSetParameter kMultiChannelMixerParam_Enable result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
}
// sets the input volume for a specific bus
- (void)setInputVolume:(UInt32)inputNum value:(AudioUnitParameterValue)value
{
OSStatus result = AudioUnitSetParameter(mMixer, kMultiChannelMixerParam_Volume, kAudioUnitScope_Input, inputNum, value, 0);
if (result) { printf("AudioUnitSetParameter kMultiChannelMixerParam_Volume Input result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
}
// sets the overall mixer output volume
- (void)setOutputVolume:(AudioUnitParameterValue)value
{
OSStatus result = AudioUnitSetParameter(mMixer, kMultiChannelMixerParam_Volume, kAudioUnitScope_Output, 0, value, 0);
if (result) { printf("AudioUnitSetParameter kMultiChannelMixerParam_Volume Output result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
}
// stars render
- (void)startAUGraph
{
printf("PLAY\n");
OSStatus result = AUGraphStart(mGraph);
if (result) { printf("AUGraphStart result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
isPlaying = true;
}
// stops render
- (void)stopAUGraph
{
printf("STOP\n");
Boolean isRunning = false;
OSStatus result = AUGraphIsRunning(mGraph, &isRunning);
if (result) { printf("AUGraphIsRunning result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
if (isRunning) {
result = AUGraphStop(mGraph);
if (result) { printf("AUGraphStop result %ld %08lX %4.4s\n", (long)result, (long)result, (char*)&result); return; }
isPlaying = false;
}
}
@end
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