因为业务需要，公司之前的语音识别功能一直使用的是国外一家公司的SDK，但是为了让用户的体验更好，并有针对性的适应用户使用场景，我们在18年底准备使用Speech Recognition 来替换之前的SDK.
苹果在iOS10 中就公开了新的API：Speech Recognition 来帮助用户使用语音识别，并且根据需要来做一些我们想要完成的功能。
老样子废话不多说，直接说正事。
首先，你需要知道如果想使用语音识别功能，那么在Info.plist 文件中需要加上以下两项。
Privacy - Microphone Usage Description 麦克风使用权限。
Privacy - Speech Recognition Usage Description 语音识别使用权限。
其次，就是需要在你需要一些带注释的Demo, 来告诉你怎么调用和使用这些API，嘿嘿~ 我刚好总结了一下并且已经写好了注释，一起来看下吧。
//
// ViewController.m
// SpeechRecognitionEngineDemo
//
// Created by 司文 on 2019/2/18.
// Copyright © 2019 司小文. All rights reserved.
//
#import "ViewController.h"
#import <AVFoundation/AVFoundation.h>
#import <Speech/Speech.h>
#import <Accelerate/Accelerate.h>
@interface ViewController ()
@property(nonatomic,strong)SFSpeechRecognizer *mySpeechRecognizer;//语音识别引擎
@property(nonatomic,strong)SFSpeechAudioBufferRecognitionRequest *myAudioBufferRecognitionRequest;//语音识别请求
@property(nonatomic,strong)SFSpeechRecognitionTask *mySpeechRecognitionTask;//语音识别任务
@property(nonatomic,strong)AVAudioEngine *myAudioEngine;//音频引擎
@property(nonatomic,strong)UILabel *lab_textDisPlay;//文本显示
@property(nonatomic,strong)UILabel *lab_volumeDisPlay;//音量显示
@property (nonatomic, assign) BOOL isRunning;//语音识别引擎是否启动
@property (nonatomic, assign) BOOL isListening;//是否监听声音
@property (nonatomic, assign) BOOL isAudioBufferAppending;//是否开始音频缓冲
@property (nonatomic, assign) float correctNum;//不同设备的修正值(内置麦克风、有线耳机、无线耳机等)
@property (nonatomic, assign) int silenceCount;//结束音频缓冲的计数
@property (nonatomic, assign) int terminalSilenceNum;//拟定结束音频缓冲的次数
@property (nonatomic, assign) int micSensitivityNum;//补充设备修正值，不需要可以为0
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.micSensitivityNum = 0;
self.terminalSilenceNum = 3;
[self makeUI];
[AVCaptureDevice requestAccessForMediaType:AVMediaTypeAudio completionHandler:^(BOOL granted) {
NSLog(@"%@",granted ? @"麦克风准许":@"麦克风不准许");
//如果允许使用麦克风
if (granted) {
[SFSpeechRecognizer requestAuthorization:^(SFSpeechRecognizerAuthorizationStatus status) {
switch (status) {
case SFSpeechRecognizerAuthorizationStatusNotDetermined:
NSLog(@"NotDetermined");
break;
case SFSpeechRecognizerAuthorizationStatusDenied:
NSLog(@"Denied");
break;
case SFSpeechRecognizerAuthorizationStatusRestricted:
NSLog(@"Restricted");
break;
case SFSpeechRecognizerAuthorizationStatusAuthorized:
NSLog(@"Authorized");
break;
default:
break;
}
}];
[self startEngine];
[self configureAudio];
}
}];
}
- (void)makeUI{
self.lab_textDisPlay = [[UILabel alloc] initWithFrame:CGRectMake(30, 100, 260, 30)];
self.lab_textDisPlay.backgroundColor = [UIColor redColor];
self.lab_textDisPlay.text = @"You can say whatever you like.";
[self.view addSubview:self.lab_textDisPlay];
self.lab_volumeDisPlay = [[UILabel alloc] initWithFrame:CGRectMake(30, 200, 260, 30)];
self.lab_volumeDisPlay.backgroundColor = [UIColor whiteColor];
self.lab_volumeDisPlay.textColor = [UIColor blackColor];
self.lab_volumeDisPlay.text = @"Volume：0";
[self.view addSubview:self.lab_volumeDisPlay];
}
- (nullable id)formatPlistDictionary:(NSDictionary*)dic{
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:dic options:NSJSONWritingPrettyPrinted error:nil];
NSString * jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];
jsonString = [jsonString uppercaseString];
//NSUTF32LittleEndianStringEncoding
NSData *jsonDataA = [jsonString dataUsingEncoding:NSUTF8StringEncoding];
return [NSJSONSerialization JSONObjectWithData:jsonDataA options:NSJSONReadingMutableContainers error:nil];
}
#pragma mark 启动音频识别引擎
- (void)startEngine{
[self startListening];
if (self.mySpeechRecognizer == nil) {
NSString *strLanguage = @"en-US";//这个参数可以选择需要的语言 例如改为 @"es" 则为西班牙语。
self.mySpeechRecognizer = [[SFSpeechRecognizer alloc] initWithLocale:[NSLocale localeWithLocaleIdentifier:strLanguage]];
[self.mySpeechRecognizer setDefaultTaskHint:SFSpeechRecognitionTaskHintConfirmation];
}
if (self.myAudioEngine == nil) {
self.myAudioEngine = [[AVAudioEngine alloc] init];
}
__weak ViewController *weakSelf = self;
AVAudioInputNode *inputNode = [self.myAudioEngine inputNode];
AVAudioFormat *format = [inputNode outputFormatForBus:0];
[inputNode installTapOnBus:0 bufferSize:1024 format:format block:^(AVAudioPCMBuffer * _Nonnull buffer, AVAudioTime * _Nonnull when) {
//获取现在收集到的音量
float volume = [weakSelf getVolume:buffer.audioBufferList];
//修正音量值
volume = volume + self.correctNum;
// NSLog(@"Currect Volume: %f", volume);
if(volume < 0){
volume = 0;
}
//展示音量值
[self.lab_volumeDisPlay performSelectorOnMainThread:@selector(setText:) withObject:[NSString stringWithFormat:@"Volume：%0.f",volume] waitUntilDone:YES];
if (volume <= self.correctNum) {
//如果音量值在范围内
if (weakSelf.isListening) {
//如果开启监听声音
if (volume > 25 || weakSelf.isAudioBufferAppending) {
//如果音量大于25，或者已经开始音频缓冲进入
if (volume < 15){
//如果小于15准备结束音频缓冲
weakSelf.silenceCount ++;
if (weakSelf.silenceCount >= self.terminalSilenceNum){
//如果到达缓冲次数，结束缓冲
weakSelf.silenceCount = 0;
weakSelf.isAudioBufferAppending = NO;
[weakSelf stopListening];//结束监听
[weakSelf.myAudioBufferRecognitionRequest appendAudioPCMBuffer:buffer];
[weakSelf.myAudioBufferRecognitionRequest endAudio];
}else{
//继续音频缓冲
[weakSelf.myAudioBufferRecognitionRequest appendAudioPCMBuffer:buffer];
}
}else{
//开始音频缓冲
weakSelf.isAudioBufferAppending = YES;
weakSelf.silenceCount = 0;
if (weakSelf.myAudioBufferRecognitionRequest == nil) {
[weakSelf startPrepareSpeechRequest];
}
[weakSelf.myAudioBufferRecognitionRequest appendAudioPCMBuffer:buffer];
}
}
}
}
}];
if (![self.myAudioEngine isRunning]) {
//如果音频引擎没有开启，则开启音频引擎
[self.myAudioEngine prepare];
[self.myAudioEngine startAndReturnError:nil];
}
//语音识别引擎启动
self.isRunning = YES;
}
#pragma mark 启动语音识别
- (void)startPrepareSpeechRequest
{
[self.mySpeechRecognitionTask cancel];
self.mySpeechRecognitionTask = nil;
self.myAudioBufferRecognitionRequest = [[SFSpeechAudioBufferRecognitionRequest alloc] init];
self.myAudioBufferRecognitionRequest.shouldReportPartialResults = NO;
__weak ViewController *weakSelf = self;
self.mySpeechRecognitionTask = [self.mySpeechRecognizer recognitionTaskWithRequest:self.myAudioBufferRecognitionRequest resultHandler:^(SFSpeechRecognitionResult * _Nullable result, NSError * _Nullable error) {
if (result != nil) {
//识别内容
weakSelf.lab_textDisPlay.text = result.bestTranscription.formattedString;
NSLog(@"%@",result.bestTranscription.formattedString);
}
if (error != nil) {
NSLog(@"%@",error.userInfo);
}
//从新开启监听
[self startListening];
self.myAudioBufferRecognitionRequest = nil;
}];
}
#pragma mark 清除
- (void)stopEngine{
[self.mySpeechRecognitionTask cancel];
self.mySpeechRecognitionTask = nil;
self.isAudioBufferAppending = NO;
[self.myAudioEngine.inputNode removeTapOnBus:0];
[self.myAudioEngine stop];
self.myAudioEngine = nil;
self.mySpeechRecognizer = nil;
self.isRunning = NO;
}
- (void)startListening
{
self.isListening = YES;
}
- (void)stopListening
{
self.isListening = NO;
}
#pragma mark 获取设备状态
- (void)configureAudio
{
AVAudioSession *audioSession = [AVAudioSession sharedInstance];
BOOL success;
NSError* error;
success = [audioSession setCategory:AVAudioSessionCategoryPlayAndRecord withOptions:AVAudioSessionCategoryOptionDefaultToSpeaker|AVAudioSessionCategoryOptionAllowBluetooth|AVAudioSessionCategoryOptionMixWithOthers error:&error];
if(!success)
NSLog(@"AVAudioSession error setCategory = %@",error.debugDescription);
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(audioRouteChanged:) name:AVAudioSessionRouteChangeNotification object:nil];
[audioSession setActive:YES error:&error];
//Restrore default audio output to BuildinReceiver
AVAudioSessionRouteDescription *currentRoute = [[AVAudioSession sharedInstance] currentRoute];
[self changeCorrectNum:currentRoute];
}
- (void)audioRouteChanged:(NSNotification*)notify {
NSDictionary *dic = notify.userInfo;
AVAudioSessionRouteDescription *currentRoute = [[AVAudioSession sharedInstance] currentRoute];
AVAudioSessionRouteDescription *oldRoute = [dic objectForKey:AVAudioSessionRouteChangePreviousRouteKey];
NSInteger routeChangeReason = [[dic objectForKey:AVAudioSessionRouteChangeReasonKey] integerValue];
NSLog(@"audio route changed: reason: %ld\n input:%@->%@, output:%@->%@",(long)routeChangeReason,oldRoute.inputs,currentRoute.inputs,oldRoute.outputs,currentRoute.outputs);
[self changeCorrectNum:currentRoute];
[self performSelector:@selector(restartEngine) withObject:nil afterDelay:0.3f];
}
- (void)restartEngine{
if (self.isRunning) {
[self stopEngine];
[self startEngine];
}
}
- (void)changeCorrectNum:(AVAudioSessionRouteDescription*)currentRoute{
self.correctNum = 65.0 + self.micSensitivityNum;
for (AVAudioSessionPortDescription *portDesc in [currentRoute inputs]){
if([portDesc.portType isEqualToString:@"MicrophoneBuiltIn"])
{
self.correctNum = 50.0 + self.micSensitivityNum;
break;
}
}
}
#pragma mark 获取音量
- (float) getVolume:(const AudioBufferList *) inputBuffer
{
float* data = (float*)malloc(inputBuffer->mBuffers[0].mDataByteSize*sizeof(float));
(memcpy(data, (float *)inputBuffer->mBuffers[0].mData, inputBuffer->mBuffers[0].mDataByteSize));//初始化data
vDSP_vsq(data, 1, data, 1, inputBuffer->mBuffers[0].mDataByteSize);
float meanVal = 0.0;
vDSP_meanv(data, 1, &meanVal, inputBuffer->mBuffers[0].mDataByteSize);
float one = 1.0;
vDSP_vdbcon(&meanVal, 1, &one, &meanVal, 1, 1, 0);
float decibel = meanVal;
free(data);
return decibel;
// numFrames*numChannels：AudioBuffer中的mDataByteSize
}
@end
这段代码中获取音量的方法，获取到的音量大小并不是很准确，并且针对有线耳机、无线耳机、iPhone内置麦克风获取的音量是不同的，初步判断是因为降噪系数的不同，导致了这一差别，所以我加入了一个修正值correctNum 来进行修正，保证各个场景下功能不受影响，当然你的场景如果特殊，请自己适配一下这个参数。
另外Buffer 的传递是这段代码中比较核心的部分，这里的判断逻辑如果是最初使用的小伙伴，可以认真看一下，其他的就木有什么了，有什么问题可以评论叫我咱们一起聊聊。
Demo下载地址：SpeechRecognitionEngineDemo