desktopCapturer API 示例展示了如何将屏幕捕获流写入
<video>
元素。
// In the renderer process.
var desktopCapturer = require('electron').desktopCapturer;
desktopCapturer.getSources({types: ['window', 'screen']}, function(error, sources) {
if (error) throw error;
for (var i = 0; i < sources.length; ++i) {
if (sources[i].name == "Electron") {
navigator.webkitGetUserMedia({
audio: false,
video: {
mandatory: {
chromeMediaSource: 'desktop',
chromeMediaSourceId: sources[i].id,
minWidth: 1280,
maxWidth: 1280,
minHeight: 720,
maxHeight: 720
}
}
}, gotStream, getUserMediaError);
return;
}
}
});
function gotStream(stream) {
document.querySelector('video').src = URL.createObjectURL(stream);
}
function getUserMediaError(e) {
console.log('getUserMediaError');
}
我尝试用以下内容替换 gotStream 函数:
function gotStream(stream) {
var fs = require('fs');
fs.writeFileSync('vid.mp4', stream);
}
这将创建一个以
[object MediaStream]
作为内容的文本文件。
如何录制此流并保存到磁盘上的文件?
我在 Demian 的 MediaRecorder 链接以及其他相关问题的帮助下回答了我自己的问题。
下面是 magnemite 的摘录,进行了一些细微的简化,并从 TypeScript 转换为 JavaScript ES5,以便大多数读者更好地理解。
var fs = require('fs');
var electron = require('electron');
var SECRET_KEY = 'Magnemite';
var recorder;
var blobs = [];
function startRecording() {
var title = document.title;
document.title = SECRET_KEY;
electron.desktopCapturer.getSources({ types: ['window', 'screen'] }, function(error, sources) {
if (error) throw error;
for (let i = 0; i < sources.length; i++) {
let src = sources[i];
if (src.name === SECRET_KEY) {
document.title = title;
navigator.webkitGetUserMedia({
audio: false,
video: {
mandatory: {
chromeMediaSource: 'desktop',
chromeMediaSourceId: src.id,
minWidth: 800,
maxWidth: 1280,
minHeight: 600,
maxHeight: 720
}
}
}, handleStream, handleUserMediaError);
return;
}
}
});
}
function handleStream(stream) {
recorder = new MediaRecorder(stream);
blobs = [];
recorder.ondataavailable = function(event) {
blobs.push(event.data);
};
recorder.start();
}
function stopRecording() {
recorder.stop();
toArrayBuffer(new Blob(blobs, {type: 'video/webm'}), function(ab) {
var buffer = toBuffer(ab);
var file = `./videos/example.webm`;
fs.writeFile(file, buffer, function(err) {
if (err) {
console.error('Failed to save video ' + err);
} else {
console.log('Saved video: ' + file);
}
});
});
}
function handleUserMediaError(e) {
console.error('handleUserMediaError', e);
}
function toArrayBuffer(blob, cb) {
let fileReader = new FileReader();
fileReader.onload = function() {
let arrayBuffer = this.result;
cb(arrayBuffer);
};
fileReader.readAsArrayBuffer(blob);
}
function toBuffer(ab) {
return Buffer.from(ab);
}
// Record for 7 seconds and save to disk
startRecording();
setTimeout(function() { stopRecording() }, 7000);
这将记录当前电子窗口 7 秒并保存到磁盘。
您应该将该流转换为二进制块。
desktopCapturer 示例展示了如何获取
Blob
。然后,您需要将 Blob
转换为 fs.writeFile
接受的内容。以下内容简短而高效:
fs.writeFile(filepath, Buffer.from(await blob.arrayBuffer()), ...);
只是提醒您应该在可用数据上使用 writestream 来避免内存泄漏。
调用
mediaRecorder.start()
时,您可以传递一个代表触发ondataavailable
的时间间隔的数字
示例:
// Assuming you already created the mediaStream
const mediaRecorder = new MediaRecorder(stream);
// starting the recording
mediaRecorder.start(1_000); // 1 second interval to trigger the dataavailable
// Create the stream file;
const writeStream = createWriteStream('your_path'); // Import this from 'fs'
const handleData = async (e: BlobEvent) => {
const arrayBuffer = await e.data.arrayBuffer(); // convert to array buffer
writeStream.write(Buffer.from(arrayBuffer));
}
const handleStop = () => {
writeStream.end();
}
mediaRecorder.addEventListener('dataavailable', handleData);
mediaRecorder.addEventListener('stop', handleStop);
通过这种方法,您可以录制长录音而不会出现延迟问题,因为您不再在内存中存储缓冲区。