我正在尝试制作一个网络广播电台，我想经常自由地更换歌曲和叠加声音。我想对音频进行速率限制，以便可以在发送之前更改提要。如果可能的话，我也想提供连续的内容
到目前为止，我们对 websockets 的尝试已经接近成功，但质量有点混乱：
这是代码：
server.jsconst express = require('express');
const app = express()
const http = require('http')
const server = http.createServer(app)
const { Server } = require("socket.io")
const io = new Server(server)
const fs = require('fs')
const SRC_PATH = 'src.wav'
const PACKET_SIZE = 6400
let PACKET = 0
function getpacket(socket){
const file_descriptor = fs.openSync(SRC_PATH, 'r', null)
const read_offset = PACKET * PACKET_SIZE
const buffer = Buffer.alloc(PACKET_SIZE)
const buffer_write_offset = 0
const num_bytes_to_read = PACKET_SIZE
const num_bytes_read = fs.readSync(file_descriptor, buffer, buffer_write_offset, num_bytes_to_read, read_offset)
fs.closeSync(file_descriptor)
console.log(`Sending packet ${PACKET}`)
socket.emit("data", buffer)
PACKET++
}
app.use('/', express.static('.'))
io.on('connection', (socket) => {
console.log("connected...")
socket.on("get", ()=>{getpacket(socket)})
})
server.listen(3000, () => {
console.log('listening on *:3000');
})
index.html<!DOCTYPE html>
<html>
<head>
<title>Testing</title>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
<script src="https://cdn.socket.io/4.5.4/socket.io.min.js"></script>
</head>
<body>
<div onclick="listen()">Click to Listen</div>
<script>
const socketio = io()
const SAMPLE_RATE = 32000 // samples/second
async function listen(){
// Set up the new audio context
const audioContext = new AudioContext()
socketio.once("data", (arrayBuff)=>{
const buffer = new Uint8Array(arrayBuff)
addTobuffer(buffer, audioContext)
})
requestData()
}
function requestData(){
socketio.emit("get")
}
async function addTobuffer(data, audioContext){
// Set up the new audio source
const audioSource = await audioContext.createBufferSource()
// create audio buffer from data,
const audioBuffer = await createAudioBuffer(audioContext,data)
// Asign the data buffer to the audioSource
audioSource.buffer = audioBuffer
// Connect the audio source to the audio context
audioSource.connect(audioContext.destination)
audioSource.start(0)
// wait until just before the end and then get more data
const packetLength = (data.length/SAMPLE_RATE)*1000-10
await new Promise(resolve=>setTimeout(resolve,packetLength))
socketio.once("data", (arrayBuff)=>{
const buffer = new Uint8Array(arrayBuff)
addTobuffer(buffer, audioContext)
})
requestData()
}
async function createAudioBuffer(audioContext,data){
/* uint8 pcm to float */
const number_of_channels = 1
const number_of_bytes = data.length
const audioBuffer = audioContext.createBuffer(number_of_channels, number_of_bytes, SAMPLE_RATE)
const nowBuffering = audioBuffer.getChannelData(0)
for (let index=0; index<number_of_bytes;index++){
const thirtytwofloat = new Float32Array(1)
thirtytwofloat[0] = (data[index]-(255/2))/255
nowBuffering[index] = thirtytwofloat[0]
}
return audioBuffer
}
</script>
</body>
</html>
并生成格式奇怪的 PCM WAV：
ffmpeg -i src.mp3 -ar 32000 -ac 1 -acodec pcm_u8 src.wav
有没有办法获得更清晰的音频输出？
好的，所以看起来像许多广播电台，如 Today's Hits （可以在 howler.js 广播示例中找到），使用 live 流媒体标准
流式传输音频首先，它们发送一条 http 消息“内容类型：音频/mpeg”，以及一些其他消息，例如 Transfer-Encoding，以向浏览器发出流即将到来的信号并保持与服务器的连接。如果我们查看 safari 上开发者控制台的网络选项卡并检查请求，我们可以看到 http 消息
根据 MDN 文档 有几种标准化的流媒体格式，wav 目前看起来不是其中之一，但 mp3 是
这是一个工作示例...
服务器.js
const EventEmitter = require('events')
const schedule = require('node-schedule')
const express = require('express')
const http = require("http")
const fs = require('fs')
const app = express()
const SAMPLE_SIZE = 32000 // samples/sec
const PACKET_SIZE = SAMPLE_SIZE // 1 second worth of data
const UPDATE_TIME = '* * * * * *' // every second
const PATH = "./src.mp3"
let PACKET_NUM = 0
const eventEmitter= new EventEmitter ()
async function getpacket(req,res){
const file_descriptor = fs.openSync(PATH, 'r', null)
const read_offset = PACKET_NUM * PACKET_SIZE
const buffer = Buffer.alloc(PACKET_SIZE)
const buffer_write_offset = 0
const num_bytes_to_read = PACKET_SIZE
const num_bytes_read = fs.readSync(file_descriptor, buffer, buffer_write_offset, num_bytes_to_read, read_offset)
fs.closeSync(file_descriptor)
console.log(`Sending packet ${PACKET_NUM} to ${req.socket.remoteAddress}`) // safari sometimes requests two streams at the same time
res.write(buffer)
}
app.get("/", (req,res)=>{
res.sendFile("index.html",{root: '.'})
})
app.get("/src.mp3", async (req,res)=>{
res.writeHead(200,"OK",{"Content-Type":"audio/mpeg"})
const updateHandler = () =>{ getpacket(req,res) }
eventEmitter.on("update", updateHandler) // On update event, send another packet
req.socket.on("close",()=>{
eventEmitter.removeListener("update",updateHandler)
console.log(`Client ${req.socket.remoteAddress} disconected from server`)
})
})
// This creates a schedule to make an update event on every second
schedule.scheduleJob(UPDATE_TIME, function(){
PACKET_NUM+=1
eventEmitter.emit("update")
})
const server = http.createServer(app)
server.listen(3000)
index.html
<!DOCTYPE html>
<html>
<head>
<title>Testing</title>
<meta http-equiv="content-type" content="text/html; charset=utf-8" />
</head>
<body>
<audio controls id="music"></audio>
<div onclick="listen()">Click to Listen</div>
<div onclick="stop()">Click to Stop</div>
<script>
async function listen(){
let music = document.getElementById('music')
music.src="/src.mp3"
music.play()
}
async function stop(){
let music = document.getElementById('music')
music.pause()
music.src=""
}
</script>
</body>
</html>
并从 wav 文件生成 mp3 文件
ffmpeg -i src.wav -ab 128k src.mp3
如果 server.js 在您的计算机上运行，您可以访问 http://localhost:3000/src.mp3 查看实时流，然后访问 http://localhost:3000/ 查看示例浏览器支持
可以使用 ffmpeg 实时更新 src.mp3