My app is supposed to take Web Audio streamed from the client, encode it as MP3, before sending it back out to clients via WebSocket.
I can currently encode and pipe to a file like this:
inbound_stream.pipe(encoder).pipe(fs.createWriteStream('audio.mp3'));
And if I already have a file on the server I can do this:
var mp3File = fs.createReadStream('audio.mp3');
mp3File.on('data', function(buffer){
io.sockets.emit('audio', { buffer: buffer });
});
However, I want to access the encoded chunks in real time, and send those out to clients - not write to a file.
What I want is this, effectively:
inbound_stream.pipe(encoder).pipe(newReadStream);
newReadStream.on('data', function(buffer){
io.sockets.emit('audio', { buffer: buffer });
});
I've looked at Duplex and Transform streams, but frankly I am still learning and the Prototyping made my head spin.
How do I do this? Thanks.
The solution below from @Nazar Sakharenko certainly does what I wanted, but the overhead of live encoding seems to make this inpossible, so writing the encoded MP3, and pre-buffering it seems to be the only way (thanks to various people for the suggestion.)
However I still have problems with this approach. New question here:
node.js - create a new ReadStream for a new file, when that file reaches a certain size
According to documentation readable.pipe(destination[, options]) the destination should be stream.Writable.
What you can do is to implement your own Writable stream:
const Writable = require('stream').Writable;
var buffer = [];
//in bytes
const CHUNK_SIZE = 102400; //100kb
const myWritable = new Writable({
write(chunk, encoding, callback) {
buffer += chunk;
if(buffer.length >= CHUNK_SIZE) {
io.sockets.emit('audio', { buffer: buffer});
buffer = [];
}
callback();
}
});
myWritable.on('finish', () => {
//emit final part if there is data to emit
if(buffer.length) {
io.sockets.emit('audio', { buffer: buffer});
}
});
inbound_stream.pipe(encoder).pipe(myWritable);
thats all.
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