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fixed 42105670 from https://gitee.com/wusongqing/docs/pulls/5372 

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en/application-dev/media/audio-capturer.md
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# Audio Capture Development
---
## ***Note***:
1. This document applies to JavaScript.
---
## **Summary**
This guide will show how a JS application can use AudioCapturer to record the audio.
Applications can use the APIs provided in this document to record raw audio files.
## **AudioCapturer Framework**
The AudioCapturer interface is one of the most important components of the audio framework.
### **Audio Capturing:**
The AudioCapturer framework provides APIs for capturing raw audio files.
## **Usage**
Here's an example of how to use AudioCapturer to capture a raw audio file.
1. Use **createAudioCapturer()** to create an AudioCapturer instance. Capturer parameters can be set in **audioCapturerOptions**.\
This instance can be used to record, control, and obtain the recording status, as well as to register a callback for notifications.
```
var audioStreamInfo = {
samplingRate: audio.AudioSamplingRate.SAMPLE_RATE_44100,
channels: audio.AudioChannel.CHANNEL_1,
sampleFormat: audio.AudioSampleFormat.SAMPLE_FORMAT_S16LE,
encodingType: audio.AudioEncodingType.ENCODING_TYPE_RAW
}
var audioCapturerInfo = {
source: audio.SourceType.SOURCE_TYPE_MIC,
capturerFlags: 1
}
var audioCapturerOptions = {
streamInfo: audioStreamInfo,
capturerInfo: audioCapturerInfo
}
let audioCapturer = await audio.createAudioCapturer(audioCapturerOptions);
var state = audioRenderer.state;
```
## When to Use
You can use the APIs provided by **AudioCapturer** to record raw audio files.
### State Check
During application development, you are advised to use **on('stateChange')** to subscribe to state changes of the **AudioCapturer** instance. This is because some operations can be performed only when the audio capturer is in a given state. If the application performs an operation when the audio capturer is not in the given state, the system may throw an exception or generate other undefined behavior.
For details about the APIs, see [AudioCapturer in Audio Management](../reference/apis/js-apis-audio.md).
**Figure 1** Audio capturer state
![](figures/audio-capturer-state.png)
## How to Develop
1. Use **createAudioCapturer()** to create an **AudioCapturer** instance.
Set parameters of the **AudioCapturer** instance in **audioCapturerOptions**. This instance is used to capture audio, control and obtain the recording status, and register a callback for notification.
2. (Optional) Subscribe to audio capturer state change events using the **on('stateChange')** API.
If an application wants to take some action based on the state updates in capturer, the application can subscribe to the state change event.
There are more events that applications can subscribe to, such as 'markReach' and 'periodReach'. Refer to [Audio](../reference/apis/js-apis-audio.md) for more details.
```js
var audioStreamInfo = {
samplingRate: audio.AudioSamplingRate.SAMPLE_RATE_44100,
channels: audio.AudioChannel.CHANNEL_1,
sampleFormat: audio.AudioSampleFormat.SAMPLE_FORMAT_S16LE,
encodingType: audio.AudioEncodingType.ENCODING_TYPE_RAW
}
var audioCapturerInfo = {
source: audio.SourceType.SOURCE_TYPE_MIC,
capturerFlags: 1
}
var audioCapturerOptions = {
streamInfo: audioStreamInfo,
capturerInfo: audioCapturerInfo
}
let audioCapturer = await audio.createAudioCapturer(audioCapturerOptions);
var state = audioRenderer.state;
```
2. (Optional) Use **on('stateChange')** to subscribe to audio renderer state changes.
If an application needs to perform some operations when the audio renderer state is updated, the application can subscribe to the state changes. For more events that can be subscribed to, see [Audio Management](../reference/apis/js-apis-audio.md).
```js
audioCapturer.on('stateChange',(state) => {
console.info('AudioCapturerLog: Changed State to : ' + state)
switch (state) {
case audio.AudioState.STATE_PREPARED:
console.info('--------CHANGE IN AUDIO STATE----------PREPARED--------------');
console.info('Audio State is : Prepared');
break;
case audio.AudioState.STATE_RUNNING:
console.info('--------CHANGE IN AUDIO STATE----------RUNNING--------------');
console.info('Audio State is : Running');
break;
case audio.AudioState.STATE_STOPPED:
console.info('--------CHANGE IN AUDIO STATE----------STOPPED--------------');
console.info('Audio State is : stopped');
break;
case audio.AudioState.STATE_RELEASED:
console.info('--------CHANGE IN AUDIO STATE----------RELEASED--------------');
console.info('Audio State is : released');
break;
default:
console.info('--------CHANGE IN AUDIO STATE----------INVALID--------------');
console.info('Audio State is : invalid');
break;
}
case audio.AudioState.STATE_PREPARED:
console.info('--------CHANGE IN AUDIO STATE----------PREPARED--------------');
console.info('Audio State is : Prepared');
break;
case audio.AudioState.STATE_RUNNING:
console.info('--------CHANGE IN AUDIO STATE----------RUNNING--------------');
console.info('Audio State is : Running');
break;
case audio.AudioState.STATE_STOPPED:
console.info('--------CHANGE IN AUDIO STATE----------STOPPED--------------');
console.info('Audio State is : stopped');
break;
case audio.AudioState.STATE_RELEASED:
console.info('--------CHANGE IN AUDIO STATE----------RELEASED--------------');
console.info('Audio State is : released');
break;
default:
console.info('--------CHANGE IN AUDIO STATE----------INVALID--------------');
console.info('Audio State is : invalid');
break;
}
});
```
3. Call the **start()** function on the AudioCapturer instance to start/resume the recording task.\
The capturer state will be STATE_RUNNING once the start is complete. The application can then begin reading buffers.
```
await audioCapturer.start();
if (audioCapturer.state == audio.AudioState.STATE_RUNNING) {
console.info('AudioRecLog: Capturer started');
} else {
console.info('AudioRecLog: Capturer start failed');
}
3. Use **start()** to start audio recording.
```
The capturer state will be **STATE_RUNNING** once the audio capturer is started. The application can then begin reading buffers.
4. Obtain the minimum buffer size to read using the **getBufferSize()** API.
```js
await audioCapturer.start();
if (audioCapturer.state == audio.AudioState.STATE_RUNNING) {
console.info('AudioRecLog: Capturer started');
} else {
console.info('AudioRecLog: Capturer start failed');
}
```
var bufferSize = await audioCapturer.getBufferSize();
console.info('AudioRecLog: buffer size: ' + bufferSize);
```
4. Use **getBufferSize()** to obtain the minimum buffer size to read.
5. Read the captured audio data and convert it to a byte stream. Call the **read()** API repeatedly to read the data
until the application wants to stop the recording. The following example shows how to write recorded data into a file.
```js
var bufferSize = await audioCapturer.getBufferSize();
console.info('AudioRecLog: buffer size: ' + bufferSize);
```
import fileio from '@ohos.fileio';
const path = '/data/data/.pulse_dir/capture_js.wav';
let fd = fileio.openSync(path, 0o102, 0o777);
if (fd !== null) {
console.info('AudioRecLog: file fd created');
}
else{
console.info('AudioRecLog: file fd create : FAILED');
return;
}
fd = fileio.openSync(path, 0o2002, 0o666);
if (fd !== null) {
console.info('AudioRecLog: file fd opened in append mode');
}
var numBuffersToCapture = 150;
while (numBuffersToCapture) {
var buffer = await audioCapturer.read(bufferSize, true);
if (typeof(buffer) == undefined) {
console.info('read buffer failed');
} else {
var number = fileio.writeSync(fd, buffer);
console.info('AudioRecLog: data written: ' + number);
}
numBuffersToCapture--;
}
```
6. Once the recording is complete, call the **stop()** API on the AudioCapturer instance to stop the recording.
```
await audioCapturer.stop();
if (audioCapturer.state == audio.AudioState.STATE_STOPPED) {
console.info('AudioRecLog: Capturer stopped');
} else {
console.info('AudioRecLog: Capturer stop failed');
}
5. Read the captured audio data and convert it to a byte stream. Call **read()** repeatedly to read the data until the application wants to stop the recording.
The following example shows how to write recorded data into a file.
```js
import fileio from '@ohos.fileio';
const path = '/data/data/.pulse_dir/capture_js.wav';
let fd = fileio.openSync(path, 0o102, 0o777);
if (fd !== null) {
console.info('AudioRecLog: file fd created');
}
else{
console.info('AudioRecLog: file fd create : FAILED');
return;
}
fd = fileio.openSync(path, 0o2002, 0o666);
if (fd !== null) {
console.info('AudioRecLog: file fd opened in append mode');
}
var numBuffersToCapture = 150;
while (numBuffersToCapture) {
var buffer = await audioCapturer.read(bufferSize, true);
if (typeof(buffer) == undefined) {
console.info('read buffer failed');
} else {
var number = fileio.writeSync(fd, buffer);
console.info('AudioRecLog: data written: ' + number);
}
numBuffersToCapture--;
}
```
7. After the recording task is complete, call the **release()** API on the AudioCapturer instance to release the stream resources.
6. Once the recording is complete, call **stop()** to stop the recording.
```
await audioCapturer.release();
if (audioCapturer.state == audio.AudioState.STATE_RELEASED) {
console.info('AudioRecLog: Capturer released');
} else {
console.info('AudioRecLog: Capturer release failed');
}
await audioCapturer.stop();
if (audioCapturer.state == audio.AudioState.STATE_STOPPED) {
console.info('AudioRecLog: Capturer stopped');
} else {
console.info('AudioRecLog: Capturer stop failed');
}
```
## **Importance of State Check**
Application developers should keep in mind that an AudioCapturer is state-based.
That is, the AudioCapturer has an internal state that the application must always check when calling recorder control APIs, because some operations are only acceptable while the capturer is in a given state.\
The system may throw an error/exception or generate other undefined behaviour if the application performs an operation while capturer is in an improper state.
7. After the task is complete, call **release()** to release related resources.
## **Other APIs**
See [AudioCapturer in the Audio API](../reference/apis/js-apis-audio.md) for more useful APIs like **getAudioTime**, **getCapturerInfo** and **getStreamInfo**.
```js
await audioCapturer.release();
if (audioCapturer.state == audio.AudioState.STATE_RELEASED) {
console.info('AudioRecLog: Capturer released');
} else {
console.info('AudioRecLog: Capturer release failed');
}
```
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