Question: keeping client connections alive after input stream interruptions

[derSoerrn95]

Description:
I'm new to RTSP and streaming. I’ve tried the server example in the gortsplib repo (https://github.com/bluenviron/gortsplib/blob/main/examples/server/main.go), but the clients get terminated when the input stream ends. My application already automatically restarts the FFmpeg process that sends the RTSP input stream.

I think it's because the sh.stream.Close() when a new stream is announced what happens, when I'm restarting my ffmpeg input process.

I would like to build a RTSP server that:

• Receives an RTSP stream from an FFmpeg process.
• Allows multiple FFmpeg clients to connect and receive the stream.
• Keeps the FFmpeg clients connected even if the input stream is interrupted (e.g., network failure or FFmpeg process termination).
• Automatically resumes feeding the stream to clients once the input stream is restored without requiring clients to reconnect.

Example FFmpeg processes:

1. Input FFmpeg process (sending to RTSP server):

   ffmpeg -i input_stream_url_cameraX -c:v copy -c:a copy -f rtsp rtsp://localhost:8554/{{ cameraX }}/stream

2. Client FFmpeg process (receiving from RTSP server and outputting to another stream):

   ffmpeg -i rtsp://localhost:8554/{{ cameraX }}/stream -c:v libx264 -c:a aac -f flv rtmp://cameraX/stream

Questions:

• Is this possible with gortsplib?
• How can I maintain the connection to the clients when the ffmpeg process that sends the input stream is restarted?

[aler9]

It is possible indeed, it's enough to create ServerStream once, delete every stream.Close() reference and reuse it.
The problem is that most clients close the connection in case of pauses of incoherent streams, that is what happens when you switch from a publisher to the next one.

The stream can be made more coherent by manually filling PayloadType, SequenceNumber and Timestamp of RTP packets in order to produce an homogeneous stream, for instance:

	nextSequenceNumber := 0

	// called when receiving a RTP packet
	ctx.Session.OnPacketRTPAny(func(medi *description.Media, _ format.Format, pkt *rtp.Packet) {
		// make sure that PayloadType is the same advertised by the first publisher
		pkt.PayloadType = 96

		// recompute SequenceNumber
		pkt.SequenceNumber = nextSequenceNumber++

		// recompute Timestamp
		pkt.Timestamp = (monothonic timestamp with a 90khz clock)

		// route the RTP packet to all readers
		sh.stream.WritePacketRTP(medi, pkt) //nolint:errcheck
	})