我正在尝试从麦克风录制声音并在OS X上实时播放。最终它将通过网络流式传输，但现在我只是尝试实现本地录制/播放。
我能够录制声音并写入文件，我可以同时使用AVCaptureSession和AVAudioRecorder。但是，我不确定如何在录制时播放音频。使用AVCaptureAudioDataOutput有效：
self.captureSession = [[AVCaptureSession alloc] init];
AVCaptureDevice *audioCaptureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
NSError *error = nil;
AVCaptureDeviceInput *audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioCaptureDevice error:&error];
AVCaptureAudioDataOutput *audioDataOutput = [[AVCaptureAudioDataOutput alloc] init];
self.serialQueue = dispatch_queue_create("audioQueue", NULL);
[audioDataOutput setSampleBufferDelegate:self queue:self.serialQueue];
if (audioInput && [self.captureSession canAddInput:audioInput] && [self.captureSession canAddOutput:audioDataOutput]) {
[self.captureSession addInput:audioInput];
[self.captureSession addOutput:audioDataOutput];
[self.captureSession startRunning];
// Stop after arbitrary time
double delayInSeconds = 4.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
[self.captureSession stopRunning];
});
} else {
NSLog(@"Couldn't add them; error = %@",error);
}
...但我不确定如何实现回调：
- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection
{
?
}
我尝试从sampleBuffer获取数据并使用AVAudioPlayer通过复制this SO answer中的代码来播放数据，但该代码在appendBytes:length:方法上崩溃
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;
NSLog(@"Length = %i",audioBuffer.mDataByteSize);
[data appendBytes:frame length:audioBuffer.mDataByteSize]; // Crashes here
}
CFRelease(blockBuffer);
NSError *playerError;
AVAudioPlayer *player = [[AVAudioPlayer alloc] initWithData:data error:&playerError];
if(player && !playerError) {
NSLog(@"Player was valid");
[player play];
} else {
NSLog(@"Error = %@",playerError);
}
编辑 CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer方法返回的OSStatus代码为-12737，根据文档为kCMSampleBufferError_ArrayTooSmall
Edit2 ：根据this mailing list response，我将size_t输出参数作为第二个参数传递给...GetAudioBufferList...。这返回40.现在我只是传入40作为硬编码值，这似乎有效（OSStatus返回值为0，至少）。
现在，播放器initWithData:error:方法会出错：
Error Domain=NSOSStatusErrorDomain Code=1954115647 "The operation couldn’t be completed. (OSStatus error 1954115647.)"我正在调查。
我已经做了很长时间的iOS编程，但到目前为止我还没有使用过AVFoundation，CoreAudio等。看起来有十几种方法可以完成同样的事情，具体取决于你想要的低级别或高级别，所以任何高级概述或框架建议都会受到赞赏。
使用AVCaptureSession录制到文件：
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification
{
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(captureSessionStartedNotification:) name:AVCaptureSessionDidStartRunningNotification object:nil];
self.captureSession = [[AVCaptureSession alloc] init];
AVCaptureDevice *audioCaptureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
NSError *error = nil;
AVCaptureDeviceInput *audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioCaptureDevice error:&error];
AVCaptureAudioFileOutput *audioOutput = [[AVCaptureAudioFileOutput alloc] init];
if (audioInput && [self.captureSession canAddInput:audioInput] && [self.captureSession canAddOutput:audioOutput]) {
NSLog(@"Can add the inputs and outputs");
[self.captureSession addInput:audioInput];
[self.captureSession addOutput:audioOutput];
[self.captureSession startRunning];
double delayInSeconds = 5.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, (int64_t)(delayInSeconds * NSEC_PER_SEC));
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
[self.captureSession stopRunning];
});
}
else {
NSLog(@"Error was = %@",error);
}
}
- (void)captureSessionStartedNotification:(NSNotification *)notification
{
AVCaptureSession *session = notification.object;
id audioOutput = session.outputs[0];
NSLog(@"Capture session started; notification = %@",notification);
NSLog(@"Notification audio output = %@",audioOutput);
[audioOutput startRecordingToOutputFileURL:[[self class] outputURL] outputFileType:AVFileTypeAppleM4A recordingDelegate:self];
}
+ (NSURL *)outputURL
{
NSArray *searchPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentPath = [searchPaths objectAtIndex:0];
NSString *filePath = [documentPath stringByAppendingPathComponent:@"z1.alac"];
return [NSURL fileURLWithPath:filePath];
}
使用AVAudioRecorder录制到文件：
NSDictionary *recordSettings = [NSDictionary
dictionaryWithObjectsAndKeys:
[NSNumber numberWithInt:AVAudioQualityMin],
AVEncoderAudioQualityKey,
[NSNumber numberWithInt:16],
AVEncoderBitRateKey,
[NSNumber numberWithInt: 2],
AVNumberOfChannelsKey,
[NSNumber numberWithFloat:44100.0],
AVSampleRateKey,
@(kAudioFormatAppleLossless),
AVFormatIDKey,
nil];
NSError *recorderError;
self.recorder = [[AVAudioRecorder alloc] initWithURL:[[self class] outputURL] settings:recordSettings error:&recorderError];
self.recorder.delegate = self;
if (self.recorder && !recorderError) {
NSLog(@"Success!");
[self.recorder recordForDuration:10];
} else {
NSLog(@"Failure, recorder = %@",self.recorder);
NSLog(@"Error = %@",recorderError);
}
答案 0 :(得分：3)
好吧，我的工作水平低于AVFoundation - 不确定是否有必要。我读了学习核心音频的第5章，并使用音频队列进行了实现。这段代码是从用于录制到文件/播放文件转换而来的，所以肯定会有一些我不小心留下的不必要的内容。另外，我实际上并没有将缓冲区重新排入输出队列（我应该be），但这只是一个概念证明这是有效的。此处列出了唯一的文件，该文件也在Github上。
//
// main.m
// Recorder
//
// Created by Maximilian Tagher on 8/7/13.
// Copyright (c) 2013 Tagher. All rights reserved.
//
#import <Foundation/Foundation.h>
#import <AudioToolbox/AudioToolbox.h>
#define kNumberRecordBuffers 3
//#define kNumberPlaybackBuffers 3
#define kPlaybackFileLocation CFSTR("/Users/Max/Music/iTunes/iTunes Media/Music/Taylor Swift/Red/02 Red.m4a")
#pragma mark - User Data Struct
// listing 4.3
struct MyRecorder;
typedef struct MyPlayer {
AudioQueueRef playerQueue;
SInt64 packetPosition;
UInt32 numPacketsToRead;
AudioStreamPacketDescription *packetDescs;
Boolean isDone;
struct MyRecorder *recorder;
} MyPlayer;
typedef struct MyRecorder {
AudioQueueRef recordQueue;
SInt64 recordPacket;
Boolean running;
MyPlayer *player;
} MyRecorder;
#pragma mark - Utility functions
// Listing 4.2
static void CheckError(OSStatus error, const char *operation) {
if (error == noErr) return;
char errorString[20];
// See if it appears to be a 4-char-code
*(UInt32 *)(errorString + 1) = CFSwapInt32HostToBig(error);
if (isprint(errorString[1]) && isprint(errorString[2])
&& isprint(errorString[3]) && isprint(errorString[4])) {
errorString[0] = errorString[5] = '\'';
errorString[6] = '\0';
} else {
// No, format it as an integer
NSLog(@"Was integer");
sprintf(errorString, "%d",(int)error);
}
fprintf(stderr, "Error: %s (%s)\n",operation,errorString);
exit(1);
}
OSStatus MyGetDefaultInputDeviceSampleRate(Float64 *outSampleRate)
{
OSStatus error;
AudioDeviceID deviceID = 0;
AudioObjectPropertyAddress propertyAddress;
UInt32 propertySize;
propertyAddress.mSelector = kAudioHardwarePropertyDefaultInputDevice;
propertyAddress.mScope = kAudioObjectPropertyScopeGlobal;
propertyAddress.mElement = 0;
propertySize = sizeof(AudioDeviceID);
error = AudioHardwareServiceGetPropertyData(kAudioObjectSystemObject,
&propertyAddress, 0, NULL,
&propertySize,
&deviceID);
if (error) return error;
propertyAddress.mSelector = kAudioDevicePropertyNominalSampleRate;
propertyAddress.mScope = kAudioObjectPropertyScopeGlobal;
propertyAddress.mElement = 0;
propertySize = sizeof(Float64);
error = AudioHardwareServiceGetPropertyData(deviceID,
&propertyAddress, 0, NULL,
&propertySize,
outSampleRate);
return error;
}
// Recorder
static void MyCopyEncoderCookieToFile(AudioQueueRef queue, AudioFileID theFile)
{
OSStatus error;
UInt32 propertySize;
error = AudioQueueGetPropertySize(queue, kAudioConverterCompressionMagicCookie, &propertySize);
if (error == noErr && propertySize > 0) {
Byte *magicCookie = (Byte *)malloc(propertySize);
CheckError(AudioQueueGetProperty(queue, kAudioQueueProperty_MagicCookie, magicCookie, &propertySize), "Couldn't get audio queue's magic cookie");
CheckError(AudioFileSetProperty(theFile, kAudioFilePropertyMagicCookieData, propertySize, magicCookie), "Couldn't set audio file's magic cookie");
free(magicCookie);
}
}
// Player
static void MyCopyEncoderCookieToQueue(AudioFileID theFile, AudioQueueRef queue)
{
UInt32 propertySize;
// Just check for presence of cookie
OSStatus result = AudioFileGetProperty(theFile, kAudioFilePropertyMagicCookieData, &propertySize, NULL);
if (result == noErr && propertySize != 0) {
Byte *magicCookie = (UInt8*)malloc(sizeof(UInt8) * propertySize);
CheckError(AudioFileGetProperty(theFile, kAudioFilePropertyMagicCookieData, &propertySize, magicCookie), "Get cookie from file failed");
CheckError(AudioQueueSetProperty(queue, kAudioQueueProperty_MagicCookie, magicCookie, propertySize), "Set cookie on file failed");
free(magicCookie);
}
}
static int MyComputeRecordBufferSize(const AudioStreamBasicDescription *format, AudioQueueRef queue, float seconds)
{
int packets, frames, bytes;
frames = (int)ceil(seconds * format->mSampleRate);
if (format->mBytesPerFrame > 0) { // Not variable
bytes = frames * format->mBytesPerFrame;
} else { // variable bytes per frame
UInt32 maxPacketSize;
if (format->mBytesPerPacket > 0) {
// Constant packet size
maxPacketSize = format->mBytesPerPacket;
} else {
// Get the largest single packet size possible
UInt32 propertySize = sizeof(maxPacketSize);
CheckError(AudioQueueGetProperty(queue, kAudioConverterPropertyMaximumOutputPacketSize, &maxPacketSize, &propertySize), "Couldn't get queue's maximum output packet size");
}
if (format->mFramesPerPacket > 0) {
packets = frames / format->mFramesPerPacket;
} else {
// Worst case scenario: 1 frame in a packet
packets = frames;
}
// Sanity check
if (packets == 0) {
packets = 1;
}
bytes = packets * maxPacketSize;
}
return bytes;
}
void CalculateBytesForPlaythrough(AudioQueueRef queue,
AudioStreamBasicDescription inDesc,
Float64 inSeconds,
UInt32 *outBufferSize,
UInt32 *outNumPackets)
{
UInt32 maxPacketSize;
UInt32 propSize = sizeof(maxPacketSize);
CheckError(AudioQueueGetProperty(queue,
kAudioQueueProperty_MaximumOutputPacketSize,
&maxPacketSize, &propSize), "Couldn't get file's max packet size");
static const int maxBufferSize = 0x10000;
static const int minBufferSize = 0x4000;
if (inDesc.mFramesPerPacket) {
Float64 numPacketsForTime = inDesc.mSampleRate / inDesc.mFramesPerPacket * inSeconds;
*outBufferSize = numPacketsForTime * maxPacketSize;
} else {
*outBufferSize = maxBufferSize > maxPacketSize ? maxBufferSize : maxPacketSize;
}
if (*outBufferSize > maxBufferSize &&
*outBufferSize > maxPacketSize) {
*outBufferSize = maxBufferSize;
} else {
if (*outBufferSize < minBufferSize) {
*outBufferSize = minBufferSize;
}
}
*outNumPackets = *outBufferSize / maxPacketSize;
}
#pragma mark - Record callback function
static void MyAQInputCallback(void *inUserData,
AudioQueueRef inQueue,
AudioQueueBufferRef inBuffer,
const AudioTimeStamp *inStartTime,
UInt32 inNumPackets,
const AudioStreamPacketDescription *inPacketDesc)
{
// NSLog(@"Input callback");
// NSLog(@"Input thread = %@",[NSThread currentThread]);
MyRecorder *recorder = (MyRecorder *)inUserData;
MyPlayer *player = recorder->player;
if (inNumPackets > 0) {
// Enqueue on the output Queue!
AudioQueueBufferRef outputBuffer;
CheckError(AudioQueueAllocateBuffer(player->playerQueue, inBuffer->mAudioDataBytesCapacity, &outputBuffer), "Input callback failed to allocate new output buffer");
memcpy(outputBuffer->mAudioData, inBuffer->mAudioData, inBuffer->mAudioDataByteSize);
outputBuffer->mAudioDataByteSize = inBuffer->mAudioDataByteSize;
// [NSData dataWithBytes:inBuffer->mAudioData length:inBuffer->mAudioDataByteSize];
// Assuming LPCM so no packet descriptions
CheckError(AudioQueueEnqueueBuffer(player->playerQueue, outputBuffer, 0, NULL), "Enqueing the buffer in input callback failed");
recorder->recordPacket += inNumPackets;
}
if (recorder->running) {
CheckError(AudioQueueEnqueueBuffer(inQueue, inBuffer, 0, NULL), "AudioQueueEnqueueBuffer failed");
}
}
static void MyAQOutputCallback(void *inUserData, AudioQueueRef inAQ, AudioQueueBufferRef inCompleteAQBuffer)
{
// NSLog(@"Output thread = %@",[NSThread currentThread]);
// NSLog(@"Output callback");
MyPlayer *aqp = (MyPlayer *)inUserData;
MyRecorder *recorder = aqp->recorder;
if (aqp->isDone) return;
}
int main(int argc, const char * argv[])
{
@autoreleasepool {
MyRecorder recorder = {0};
MyPlayer player = {0};
recorder.player = &player;
player.recorder = &recorder;
AudioStreamBasicDescription recordFormat;
memset(&recordFormat, 0, sizeof(recordFormat));
recordFormat.mFormatID = kAudioFormatLinearPCM;
recordFormat.mChannelsPerFrame = 2; //stereo
// Begin my changes to make LPCM work
recordFormat.mBitsPerChannel = 16;
// Haven't checked if each of these flags is necessary, this is just what Chapter 2 used for LPCM.
recordFormat.mFormatFlags = kAudioFormatFlagIsBigEndian | kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
// end my changes
MyGetDefaultInputDeviceSampleRate(&recordFormat.mSampleRate);
UInt32 propSize = sizeof(recordFormat);
CheckError(AudioFormatGetProperty(kAudioFormatProperty_FormatInfo,
0,
NULL,
&propSize,
&recordFormat), "AudioFormatGetProperty failed");
AudioQueueRef queue = {0};
CheckError(AudioQueueNewInput(&recordFormat, MyAQInputCallback, &recorder, NULL, NULL, 0, &queue), "AudioQueueNewInput failed");
recorder.recordQueue = queue;
// Fills in ABSD a little more
UInt32 size = sizeof(recordFormat);
CheckError(AudioQueueGetProperty(queue,
kAudioConverterCurrentOutputStreamDescription,
&recordFormat,
&size), "Couldn't get queue's format");
// MyCopyEncoderCookieToFile(queue, recorder.recordFile);
int bufferByteSize = MyComputeRecordBufferSize(&recordFormat,queue,0.5);
NSLog(@"%d",__LINE__);
// Create and Enqueue buffers
int bufferIndex;
for (bufferIndex = 0;
bufferIndex < kNumberRecordBuffers;
++bufferIndex) {
AudioQueueBufferRef buffer;
CheckError(AudioQueueAllocateBuffer(queue,
bufferByteSize,
&buffer), "AudioQueueBufferRef failed");
CheckError(AudioQueueEnqueueBuffer(queue, buffer, 0, NULL), "AudioQueueEnqueueBuffer failed");
}
// PLAYBACK SETUP
AudioQueueRef playbackQueue;
CheckError(AudioQueueNewOutput(&recordFormat,
MyAQOutputCallback,
&player, NULL, NULL, 0,
&playbackQueue), "AudioOutputNewQueue failed");
player.playerQueue = playbackQueue;
UInt32 playBufferByteSize;
CalculateBytesForPlaythrough(queue, recordFormat, 0.1, &playBufferByteSize, &player.numPacketsToRead);
bool isFormatVBR = (recordFormat.mBytesPerPacket == 0
|| recordFormat.mFramesPerPacket == 0);
if (isFormatVBR) {
NSLog(@"Not supporting VBR");
player.packetDescs = (AudioStreamPacketDescription*) malloc(sizeof(AudioStreamPacketDescription) * player.numPacketsToRead);
} else {
player.packetDescs = NULL;
}
// END PLAYBACK
recorder.running = TRUE;
player.isDone = false;
CheckError(AudioQueueStart(playbackQueue, NULL), "AudioQueueStart failed");
CheckError(AudioQueueStart(queue, NULL), "AudioQueueStart failed");
CFRunLoopRunInMode(kCFRunLoopDefaultMode, 10, TRUE);
printf("Playing through, press <return> to stop:\n");
getchar();
printf("* done *\n");
recorder.running = FALSE;
player.isDone = true;
CheckError(AudioQueueStop(playbackQueue, false), "Failed to stop playback queue");
CheckError(AudioQueueStop(queue, TRUE), "AudioQueueStop failed");
AudioQueueDispose(playbackQueue, FALSE);
AudioQueueDispose(queue, TRUE);
}
return 0;
}