以数值显示 SPL 级别，而不是改变颜色强度

Posted 2023-02-25

【中文标题】以数值显示 SPL 级别，而不是改变颜色强度

【英文标题】：Display SPL level in numeric value rather than varying colour intensity

【发布时间】：2017-03-14 02:53:55

【问题描述】：

我正在尝试为 ios 中的 uni 项目开发 SPL 计，我一直在关注有关如何获取音频输入和显示输入电平的在线教程，但是本教程将输入显示为不同强度的颜色和也处于 RMS 值，而不是峰值。我发现了与此相关的两个先前的帖子，但是它们的信息量不足以提供帮助，并且作为堆栈溢出的新手，我无法就所提供的答案寻求进一步的支持。

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我一直在关注的项目教程是在 Objective-C 而不是 Swift 中运行的，因为它是一个旧的视频集合，但是它（几乎）可以满足我的需要，所以在我理解之前没有尝试更改为 swift我在做什么以及为什么要这样做。

这是录音和输入电平监控的完整代码：

//Lynda.Com Tutorial Project


#import "ViewController.h"

@import AudioToolbox;
@import AVFoundation;

#define kOutputBus 0
#define kInputBus 1

@interface ViewController ()

@property (nonatomic,weak) IBOutlet UIView *indicatorView;

@end

@implementation ViewController

static AudioComponentInstance audioUnit;

- (void)viewDidLoad 
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    [self setupAudio];


- (void) setupAudio 
    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);

    OSStatus status = AudioComponentInstanceNew(comp, &audioUnit);
    if (status != noErr) 
        NSAssert(status == noErr,@"Error");
    

    AudioStreamBasicDescription audioFormat;

    audioFormat.mSampleRate = 44100.00;
    audioFormat.mFormatID = kAudioFormatLinearPCM;
    audioFormat.mFormatFlags = kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsPacked;
    audioFormat.mFramesPerPacket = 1;
    audioFormat.mChannelsPerFrame = 1;
    audioFormat.mBitsPerChannel = 16;
    audioFormat.mBytesPerFrame = audioFormat.mChannelsPerFrame * sizeof(SInt16);
    audioFormat.mBytesPerPacket = audioFormat.mFramesPerPacket * audioFormat.mBytesPerFrame;

    UInt32 flag = 1;
    status = AudioUnitSetProperty(audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Input, kInputBus, &flag, sizeof(flag));
    if (status != noErr) 
        NSAssert(status == noErr,@"Error");
    

    flag = 0;
    status = AudioUnitSetProperty(audioUnit, kAudioOutputUnitProperty_EnableIO, kAudioUnitScope_Output, kOutputBus, &flag, sizeof(flag));
    if (status != noErr) 
        NSAssert(status == noErr,@"Error");
    

    status = AudioUnitSetProperty(audioUnit , kAudioUnitProperty_StreamFormat, kAudioUnitScope_Output, kInputBus, &audioFormat, sizeof(audioFormat));
    if (status != noErr) 
        NSAssert(status == noErr,@"Error");
    

    AURenderCallbackStruct callbackStruct;
    callbackStruct.inputProc = recordingCallback;
    callbackStruct.inputProcRefCon = (__bridge void*)self;

    status = AudioUnitSetProperty(audioUnit , kAudioOutputUnitProperty_SetInputCallback, kAudioUnitScope_Global, kInputBus, &callbackStruct, sizeof(callbackStruct));
    if (status != noErr) 
        NSAssert(status == noErr,@"Error");
    

    status = AudioUnitInitialize(audioUnit);
    if (status != noErr) 
        NSAssert(status == noErr,@"Error");
    



static OSStatus recordingCallback(

                                  void *inRefCon,
                                  AudioUnitRenderActionFlags *ioActionFlags,
                                  const AudioTimeStamp *inTimeStamp,
                                  UInt32 inBusNumber,
                                  UInt32 inNumberFrames,
                                  AudioBufferList *ioData

                            ) 

    AudioBuffer buffer;

    buffer.mNumberChannels = 1;
    buffer.mDataByteSize = inNumberFrames * sizeof(SInt16);
    buffer.mData = malloc(buffer.mDataByteSize);

    AudioBufferList bufferList;
    bufferList.mNumberBuffers = 1;
    bufferList.mBuffers[0] = buffer;

    OSStatus status = AudioUnitRender(audioUnit , ioActionFlags, inTimeStamp, inBusNumber, inNumberFrames, &bufferList);
    if (status != noErr) 
        printf("Error\n");
        return -1;
    

    SInt16 *frameBuffer = buffer.mData;

    double totalAmplitude = 0;

    for (int i = 0; i < inNumberFrames; i++) 
        //printf("%i\n",frameBuffer[i]);
        totalAmplitude += frameBuffer[i] * frameBuffer[i];
    

    totalAmplitude /= inNumberFrames;

    totalAmplitude = sqrt(totalAmplitude);

    float alphaFloat = totalAmplitude / (float)SHRT_MAX * 2;

    dispatch_async(dispatch_get_main_queue(), ^
        ViewController *viewController = (__bridge ViewController*)inRefCon;
        viewController.indicatorView.backgroundColor = [UIColor colorWithRed:1.0 green:0 blue:0 alpha:alphaFloat];
    );

    return noErr;


- (IBAction)recordButtonPressed:(id)sender 
    NSError *error;
    [[AVAudioSession sharedInstance] setActive:YES error:&error];
    if (error != nil) 
        NSAssert(error == nil, @"Error");
    
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryRecord error:&error];
    if (error != nil) 
        NSAssert(error == nil, @"Error");
    

    [[AVAudioSession sharedInstance] requestRecordPermission:^(BOOL granted) 
        if (granted) 
            OSStatus status = AudioOutputUnitStart(audioUnit);
            if (status != noErr) 
                NSAssert(status == noErr,@"Error");
            
         else 
            NSAssert(NO, @"Error");
        
    ];


- (IBAction)stopButtonPressed:(id)sender 
    OSStatus status = AudioOutputUnitStop(audioUnit);
    if (status != noErr) 
        NSAssert(status == noErr,@"Error");
    
    NSError *error;
    [[AVAudioSession sharedInstance] setActive:NO error:&error];
    if (error != nil) 
        NSAssert(error == nil, @"Error");
    
    self.indicatorView.backgroundColor = [UIColor clearColor];


- (void)didReceiveMemoryWarning 
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.


- (void) dealloc 
    OSStatus status = AudioComponentInstanceDispose(audioUnit);
    if (status != noErr) 
        NSAssert(status == noErr,@"Error");
    


@end

我需要帮助理解的是，因为我相信这里的这段代码：

dispatch_async(dispatch_get_main_queue(), ^
    ViewController *viewController = (__bridge ViewController*)inRefCon;
    viewController.indicatorView.backgroundColor = [UIColor colorWithRed:1.0 green:0 blue:0 alpha:alphaFloat];

这是 UIView 被告知显示不同强度的红色的地方，我想要将其更改为不同的数字。

RMS 到 dBSPL 的值不是问题，它在正在运行的应用程序中的红色框的位置显示为不断变化的值，我真的可以通过一些帮助来做，所有帮助都非常感谢提前！

谢谢，

克里斯

【参考方案1】：

您要显示的值在变量 alphaFloat 中。你需要给你的 ViewController 添加一个 UILabel 属性，你可以称之为dBSPLView。然后在 viewController.indicatorView.backgroundColor 被改变的地方你会做这样的事情：

viewController.dBSPLView.text = [NSString stringWithFormat:@"%f", alphaFloat];