What is best way to deal with client network errors?

[Olex1313]

Hello, I'm currently working on my course project in university and my goal is to write simple rtsp proxy with error-prone client.

Generally speaking I have a ip-cam with rtsp stream in lecture room and ffmpeg-based scheduled scripts somewhere to save lecture record. But due to network issues sometimes camera is unavailable which causes ffmpeg to throw an error.

I want to put a proxy between camera and client, and when network error occurs send some picture with "please stand by". I'm not that familiar with network programming and RTSP protocol, but can I just catch error after play request and directly write packets to ServerStream? Or is there some way to do it more clearly?

// start playing
	_, err = rc.Play(nil)
	if err.Error() == "EOF" {
		stream.WritePacketRTP()
	}
	if err != nil {
		return err // "EOF"
	}

[aler9]

Hello, this task is difficult since it involves creating a continuous and coherent H264 stream (assuming your camera uses H264 as its video codec). The RTSP protocol only implements the outer layer that wraps the H264 stream. When a camera disconnects, the H264 stream goes missing and it's impossible to recreate it or insert frames in between.

The easiest way i can think of implementing this consists in:

1. Connect to the stream, start decoding H264 access units:
   https://github.com/bluenviron/gortsplib/blob/main/examples/client-read-format-h264/main.go

2. Create a server that encodes the H264 access units and makes them available to any client:
   https://github.com/bluenviron/gortsplib/blob/main/examples/server/main.go

   H264 encoder is here:
   https://pkg.go.dev/github.com/bluenviron/gortsplib/[email protected]/pkg/formats/rtph264#Encoder

3. Keep the last H264 access unit stored in memory

4. When the RTSP client disconnects, start a routine that periodically publishes the last H264 access unit, and in the meanwhile start another RTSP client

5. When the new RTSP client is connected and ready, stop the routine and attach the new RTSP client to the server again

[Olex1313]

Thanks, I'll try to make some cache for packages and will try to re-send it

[danielamar101]

Were you able to implement this approach @Olex1313 ?