语音表达是人类最直接的表达方式之一，语音输入不像手势识别的AirTap操作久了会让用户觉得手部酸痛。对于HoloLens，语音输入是三大基本输入方式之一，广泛地运用在各种交互场所上。Hololens上语音输入有三种形式，分别是：
- 语音命令 Voice Command
- 听写 Diction
- 语法识别 Grammar Recognizer
本文主要介绍语音命令，对于HoloLens的交互使用来说，语音命令也是最经常被使用的语音输入形式。
语音命令 Voice Command
使用语音命令，首先的确保在应用中已经开启 microphone 的功能特性，具体设置是 Edit -> Project Settings -> Player -> Settings for Windows Store -> Publishing Settings -> Capabilities 下找到 microphone 特性并勾上。
对于语音命令的使用，开发者通过声明 Dictionary<string, UnityEvent> 来设定语音命令的关键字和对应行为，并由这个注册 Dictionary 来初始化 KeywordRecognizer ，编写行为动作函数。当用户说出关键词时，预设的动作就会被调用，从而实现语音命令的功能。
**KeywordRecognizer.cs**
using UnityEngine.Windows.Speech;
using System.Collections.Generic;
using System.Linq;
public class KeywordManager : MonoBehavior
{
KeywordRecognizer keywordRecognizer;
Dictionary<string, System.Action> keywords = new Dictionary<string, System.Action>();
void Start()
{
//初始化关键词
keywords.Add("activate", () =>
{
// 想执行的行为
});
keywordRecognizer = new KeywordRecognizer(keywords.Keys.ToArray());
keywordRecognizer.OnPhraseRecognized += KeywordRecognizer_OnPhraseRecognized;
//开始识别
keywordRecognizer.Start();
}
private void KeywordRecognizer_OnPhraseRecognized(PhraseRecognizedEventArgs args)
{
System.Action keywordAction;
// 如果识别到关键词就调用
if (keywords.TryGetValue(args.text, out keywordAction))
{
keywordAction.Invoke();
}
}
void OnDestroy()
{
keywordRecognizer.Dispose();
}
}
下面是对 KeywordRecognizer.cs 脚本的一个应用：
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将KeywordRecognizer.cs 脚本中的关键词和动作操作的注册公开 Inspector 面板中，来代替在脚本中代码添加注册语音事件，这样可以在unity没运行的时候动态地添加语音命令。其脚本修改如下：
**KeywordRecognizer.cs**
using System.Collections.Generic;
using System.Linq;
using UnityEngine;
using UnityEngine.Events;
using UnityEngine.Windows.Speech;
namespace HoloToolkit
{
public class KeywordManager : MonoBehaviour
{
//将此结构体暴露在Inspector面板中实现语音关键词和动作的添加
public struct KeywordAndResponse
{
[Tooltip("The keyword to recognize.")]
public string Keyword;
[Tooltip("The UnityEvent to be invoked when the keyword is recognized.")]
public UnityEvent Response;
}
// This enumeration gives the manager two different ways to handle the recognizer. Both will
// set up the recognizer and add all keywords. The first causes the recognizer to start
// immediately. The second allows the recognizer to be manually started at a later time.
//这个枚举用于选择是立即进行语音识别 还是 过段时间进行手动设置进行语音识别
public enum RecognizerStartBehavior { AutoStart, ManualStart };
[Tooltip("An enumeration to set whether the recognizer should start on or off.")]
public RecognizerStartBehavior RecognizerStart;
[Tooltip("An array of string keywords and UnityEvents, to be set in the Inspector.")]
public KeywordAndResponse[] KeywordsAndResponses;
private KeywordRecognizer keywordRecognizer;
private Dictionary<string, UnityEvent> responses;
void Start()
{
if (KeywordsAndResponses.Length > 0)
{
// Convert the struct array into a dictionary, with the keywords and the keys and the methods as the values.
// This helps easily link the keyword recognized to the UnityEvent to be invoked.
//将struct数组转换为字典，将struct中的Keyword转换为字典的关键字，UnityEven转换为字典的方法
responses = KeywordsAndResponses.ToDictionary(keywordAndResponse => keywordAndResponse.Keyword,
keywordAndResponse => keywordAndResponse.Response);
//由注册的关键字来初始化KeywordRecognizer
keywordRecognizer = new KeywordRecognizer(responses.Keys.ToArray());
keywordRecognizer.OnPhraseRecognized += KeywordRecognizer_OnPhraseRecognized;
//如果RecognizerStartBehavior枚举值是AutoStart的话，就立马开始语音识别
if (RecognizerStart == RecognizerStartBehavior.AutoStart)
{
keywordRecognizer.Start();
}
}
else
{
Debug.LogError("Must have at least one keyword specified in the Inspector on " + gameObject.name + ".");
}
}
void OnDestroy()
{
if (keywordRecognizer != null)
{
StopKeywordRecognizer();
keywordRecognizer.OnPhraseRecognized -= KeywordRecognizer_OnPhraseRecognized;
keywordRecognizer.Dispose(); //取消语音识别后必须Dispose掉，由GC回收，节省资源
}
}
private void KeywordRecognizer_OnPhraseRecognized(PhraseRecognizedEventArgs args)
{
UnityEvent keywordResponse;
// Check to make sure the recognized keyword exists in the methods dictionary, then invoke the corresponding method.
// 如果识别到关键词就调用
if (responses.TryGetValue(args.text, out keywordResponse))
{
keywordResponse.Invoke();
}
}
/// <summary>
/// Make sure the keyword recognizer is off, then start it.
/// Otherwise, leave it alone because it's already in the desired state.
/// </summary>
public void StartKeywordRecognizer()
{
if (keywordRecognizer != null && !keywordRecognizer.IsRunning)
{
keywordRecognizer.Start();
}
}
/// <summary>
/// Make sure the keyword recognizer is on, then stop it.
/// Otherwise, leave it alone because it's already in the desired state.
/// </summary>
public void StopKeywordRecognizer()
{
if (keywordRecognizer != null && keywordRecognizer.IsRunning)
{
keywordRecognizer.Stop();
}
}
}
}
- 在脚本中可以看到首先声明一个结构体，将其暴露在在Inspector面板，动态在unity中注册语音关键词和对应的动作函数，在 Start() 函数中将这个结构体相关的数组转换为一个Dictionary，将struct中的Keyword转换为字典的关键字，UnityEven转换为字典的方法。
- 脚本声明了一个enum，给了两种不同的状态来处理识别，一个是立即开始语音识别，另一个是手动设置开始识别。
- 当取消语音识别后，必须将 KeywordRecognizer 给 Dispose() 掉，随后GC会自动进行垃圾回收，以节省资源消耗。
