# 語音串接 - Web Speech Api

[toc]

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| Type | Web Speech Api |
| -------- | -------- |
| STT (speech-to-text) | SpeechRecognition |
| TTS (text-to-speech) | SpeechSynthesis |

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## SpeechRecognition

### Basic Techniques
<div style="font-size: 12px; text-align: center;">figure from MDN website</div>

* Asynthesized

* SpeechRecognition use a server-based recognition engine in the browser. Therefore, it requires a condition of online.

* To do speech recognition offline, the speech recognition engine must be embedded within the browser.

* Language set required to help recognize the voice (default: en)

On some browsers, like Chrome, using Speech Recognition on 
a web page involves a server-based recognition engine. 
Your audio is sent to a web service for recognition processing, 
so it won't work offline.

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---

### Voice Stream in the SpeechRecognition setting

* SpeechRecognition.continuous
* Controls whether continuous results are returned for each recognition, or only a single result. Defaults to single (false.)
* SpeechRecognition.interimResults
* Controls whether interim results should be returned (true) or not (false.) Interim results are results that are not yet final (e.g. the SpeechRecognitionResult.isFinal property is false.)

var SpeechRecognition =
  window.SpeechRecognition || window.webkitSpeechRecognition;
if (SpeechRecognition) { 
    //some browser does not support Web Speech Recognition API, 
    //ex. Firefox use Firefox Nightly instead
    speechRecognition = new SpeechRecognition();
    //both properties set true to make the voice result use stream 
    speechRecognition.continuous = true;
    speechRecognition.interimResults = true;
}

---

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## SpeechSynthesis

### Basic Techniques
<div style="font-size: 12px; text-align: center;">figure from intersec website</div>

* Synthesized

* SpeechSynthesis run in the browser without any server support

* Main Useful Parameters:
* voice select (man/woman)
* rate value (voice rate number)
* language setting

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## Reference

[Web Speech API - Speech Recognition (from mozilla wiki)](https://wiki.mozilla.org/Web_Speech_API_-_Speech_Recognition)

[SpeechRecognition_MDN](https://developer.mozilla.org/en-US/docs/Web/API/SpeechRecognition)

[SpeechSynthesis_MDN](https://developer.mozilla.org/en-US/docs/Web/API/SpeechSynthesis)

[Web Speech API - Creating a web interface with 0 clicks](https://techtalk.intersec.com/2023/03/web-speech-api-creating-a-web-interface-with-0-clicks/)