Unreliable RTCDataChannel

mediasoup libraries
2

This is a known problem. Magic doe snot exist. mediasoup cannot buffer all data that receivers must receive.

  • Alice and Bob join the same mediasoup Router.
  • Alice create a WebRTC reliable DataProducer and Bob consumes its data by creating a WebRTC reliable DataConsumer.
  • Alice sends ton of data. Bob has poor downlink quality.
  • Eventually mediasoup (the SCTP stack) cannot send that many messages to Bob and its sending buffer gets filled so some messages are lost.

Workaround (the bad way)

Set a higher sctpSendBufferSize: mediasoup :: API

Proper solution

  • Create a DirectTransport in mediasoup and create a DataConsumer on it to consume from Alices WebRTC DataProducer`.
  • Create another DirectTransport and a fake DataProducer on it both associated to Bob (such a fake DataProducer is required due the design of producers and consumers).
  • Make the WebRTC DataConsumer of Bob consume from such a DataProducer instead of consuming from the original WebRTC DataProducer.
  • When a message is received in mediasoup by Alice’s direct DataConsumer, take the message and call dataConsumer.send(message or whatever) in the WebRTC DataConsumer of Bob.

And here the thing:

  • You must check the async result of dataConsumer.send() (see the API) and you must properly use the dataConsumer.getBufferedAmount() method and the dataConsumer.on(“bufferedamountlow”) event and buffer the messages in Node land (within your app) is needed, so if there is a memory leak it will be a failure in your Node app rather than in mediasoup.

PS: I know this is complex and that’s why this is gonna change in mediasoup v4 eventually, but unfortunately I cannot give more tips about this solution. Hope it helps.

Using non-zero streamId for RTC dataProducer