Question

我正在尝试使用SDK 8.1上的Core Audio和AVAudioSession开发一个分析来自麦克风的音频流的应用。使用苹果文档中的点点滴滴以及乐于助人的博主，我成功地制作了一个成功的程序

设置AVAudioSession的属性。
激活AVAudioSession。
实例化音频组件实例。
设置音频单元的属性，例如。回调函数和AudioStreamDescription。
初始化音频单元。

但该程序很难开始录制 - AudioOutputUnitStart函数失败，返回码为-500。这是为什么？ [以下代码按原样运行，如果它保存为ViewController.m并在单页xcode模板中使用。即使它不是最小的，我也尽量保持尽可能小。]

#import "ViewController.h"
@import AVFoundation;
@import AudioUnit;
#define kInputBus 1
AudioComponentInstance *audioUnit = NULL;
float *convertedSampleBuffer = NULL;
int status = 0;
static OSStatus recordingCallback(void *inRefCon,
                                  AudioUnitRenderActionFlags *ioActionFlags,
                                  const AudioTimeStamp *inTimeStamp,
                                  UInt32 inBusNumber,
                                  UInt32 inNumberFrames,
                                  AudioBufferList *ioData) {
    AudioBufferList *bufferList;
    OSStatus status;
    status = AudioUnitRender(*audioUnit,
                             ioActionFlags,
                             inTimeStamp,
                             inBusNumber,
                             inNumberFrames,
                             bufferList);
    printf("%d", status); printf("%s", " is the return code of AudioUnitRender from the recordingCallback.\n");
    // DoStuffWithTheRecordedAudio(bufferList);
    return noErr;
}
int myAudio() {
    AVAudioSession *mySession = [AVAudioSession sharedInstance];
    [mySession setCategory: AVAudioSessionCategoryRecord error: nil];
    [mySession setMode: AVAudioSessionModeMeasurement error: nil];
    [mySession setPreferredSampleRate:44100 error:nil];
    [mySession setPreferredIOBufferDuration:0.02 error:nil];
    [mySession setActive: YES error: nil];
    audioUnit = (AudioUnit*)malloc(sizeof(AudioUnit));
    AudioComponentDescription desc;
    desc.componentType = kAudioUnitType_Output;
    desc.componentSubType = kAudioUnitSubType_RemoteIO;
    desc.componentManufacturer = kAudioUnitManufacturer_Apple;
    desc.componentFlags = 0;
    desc.componentFlagsMask = 0;
    AudioComponent comp = AudioComponentFindNext(NULL, &desc);
    status = AudioComponentInstanceNew(comp, audioUnit);
    printf("%d", status); printf("%s", " is the return code of Instantiating a new audio component instance.\n");
    UInt32 enable = 1;
    status = AudioUnitSetProperty(*audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, kInputBus, &enable, sizeof(enable));
    printf("%d", status); printf("%s", " is the return code of EnablingIO on the audiounit.\n");
    AudioStreamBasicDescription streamDescription = {0};
    streamDescription.mSampleRate       = 44100;
    streamDescription.mFormatID         = kAudioFormatLinearPCM;
    streamDescription.mFormatFlags      = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
    streamDescription.mFramesPerPacket  = 1;
    streamDescription.mChannelsPerFrame = 1;
    streamDescription.mBitsPerChannel   = 16;
    streamDescription.mBytesPerPacket   = 2;
    streamDescription.mBytesPerFrame    = 2;
    status = AudioUnitSetProperty(*audioUnit, kAudioUnitProperty_StreamFormat, kAudioUnitScope_Input, 0, &streamDescription, sizeof(streamDescription));
    printf("%d", status); printf("%s", " is the return code of setting the AudioStreamDescription.\n");
    AURenderCallbackStruct callbackStruct;
    callbackStruct.inputProc = recordingCallback;
    callbackStruct.inputProcRefCon = NULL;
    status = AudioUnitSetProperty(*audioUnit,
                                  kAudioOutputUnitProperty_SetInputCallback,
                                  kAudioUnitScope_Global,
                                  kInputBus,
                                  &callbackStruct,
                                  sizeof(callbackStruct));
    printf("%d", status); printf("%s", " is the return code of setting the recording callback on the audiounit\n");
    status = AudioUnitInitialize(*audioUnit);
    printf("%d", status); printf("%s", " is the return code of initializing the audiounit.\n");
    status = AudioOutputUnitStart(*audioUnit);
    printf("%d", status); printf("%s", " is the return code of Starting the audioUnit\n");
    return noErr;
}

@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    myAudio();
    [NSThread sleepForTimeInterval:1];
    exit(0);
}
- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
@end

除了返回-500的最后一个语句之外，所有printf语句都返回0。

Answer 1

问题中提供的代码有两个错误：

应在音频设备启动后创建音频会话。
as @jn_pdx指出必须分配bufferList。

这是一个完整的ViewController.m，能够录制，并且如果激活了评论块，也可以播放（如果您的目标是播放并激活音频会话块，则从{{1}更改类别} Record。Michael Tyson用于发布我构建的基础的信用。

PlayAndRecord

为什么AudioOutputUnitStart（）失败并返回代码-500？

1 个答案: