# Stream Desktop/Video/Webcam to Kodi/Beamer/other PCs
Gregor and I had a closer look at the following projects:

# Laplace
Simple WebRTC implementation in GO: https://github.com/adamyordan/laplace.git
Simple to compile and just works.
WebRTC actually uses SRTP (Secure Real-time Transport Protocol). 

IPv6+IPv4, and no TLS:

    ./laplace -addr "[::]:8080" -tls=false

## WebRTC signaling

* https://developer.mozilla.org/en-US/docs/Web/API/WebRTC_API/Signaling_and_video_calling
* https://www.tutorialspoint.com/webrtc/webrtc_signaling.htm
* https://www.html5rocks.com/en/tutorials/webrtc/infrastructure/
* https://github.com/topics/webrtc-signaling

# gstreamer
* Supports RTP
* Supports webcam capture via v4l (video for linux)
* Supports screen capture via xmanager/ximagesrc
* Interesting URLs:
  * WebRTC in one direction only: https://stackoverflow.com/questions/57430215/how-to-use-webrtcbin-create-offer-only-receive-video
  * gstreamer to VLC via RTP: https://stackoverflow.com/questions/13154983/gstreamer-rtp-stream-to-vlc
  * https://github.com/intel/gstreamer-media-SDK/issues/138
  * https://developer.ridgerun.com/wiki/index.php?title=GstWebRTC_Pipelines
  * https://developer.ridgerun.com/wiki/index.php?title=GstWebRTC_-_H264-Opus_Examples#Receive_Pipeline

## WebRTC
gstreamer has a WebRTC implementation.
The examples at https://github.com/centricular/gstwebrtc-demos.git work once

    export OPENSSL_CONF=''

has been set (see https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/issues/811)

There's a new recvonly example:

* https://github.com/centricular/gstwebrtc-demos/commit/000cfb6cd817ca0f07d761795b352a8b8b9074f8
* `sendonly/webrtc-recvonly-h264.c`

## gstreamer examples
    gst-launch-1.0 -v playbin uri=file:///home/philipp/tmp/GerisGame.mp4
    
    # send
    gst-launch-1.0 ximagesrc ! videoconvert ! videoscale ! video/x-raw,width=800,height=600 ! vp8enc ! rtpvp8pay ! udpsink host=239.255.12.42 port=5004
    # receive
    gst-launch-1.0 udpsrc address=239.255.12.42 port=5004 caps="application/x-rtp, media=(string)video, clock-rate=(int)90000, encoding-name=(string)VP8-DRAFT-IETF-01, payload=(int)96, ssrc=(uint)2990747501, clock-base=(uint)275641083, seqnum-base=(uint)34810" ! rtpvp8depay ! vp8dec ! autovideosink
    
    # send
    gst-launch-1.0 -v ximagesrc ! videoconvert ! videoscale ! video/x-raw,format=I420,width=800,height=600,framerate=25/1 ! jpegenc ! rtpjpegpay ! udpsink host=239.255.12.42 port=5004
    # receive
    gst-launch-1.0 udpsrc address=239.255.12.42 port=5004 ! application/x-rtp,encoding-name=JPEG,payload=26 ! rtpjpegdepay ! jpegdec ! autovideosink


* https://stackoverflow.com/questions/33747500/using-gstreamer-to-capture-screen-and-show-it-in-a-window/33822024#33822024
* http://www.einarsundgren.se/gstreamer-basic-real-time-streaming-tutorial/
* https://gist.github.com/tetkuz/0c038321d05586841897
* https://gist.github.com/esrever10/7d39fe2d4163c5b2d7006495c3c911bb
* https://gist.github.com/nebgnahz/26a60cd28f671a8b7f522e80e75a9aa5
* https://salsa.debian.org/debconf-video-team/ansible/-/blob/master/roles/voctomix/templates/videoteam-stream.j2
* https://github.com/xfxf/video-scripts/blob/master/michael/youtube-live.sh
  (and others in the same repo)

## gstreamer webrtc, another example

* blog post: https://aweirdimagination.net/2020/07/05/gstreamer-webrtc/
* code: https://git.aweirdimagination.net/perelman/minimal-webrtc-gstreamer
    
## websockets

connecting to websockets (plus gstreamer and v4l2sink)

https://michael.stapelberg.ch/posts/2020-06-06-iphone-camera-linux-v4l2loopback/

	# send
	laplace / chromium

	# receive
	websocat --insecure "wss://localhost:8080/ws_connect?id=cranky_kind_chipmunk"

## more v4l2loopback/v4l2sink

	# send
	gst-launch-1.0 videotestsrc ! v4l2sink device=/dev/video42

	# receive
	cvlc v4l2:///dev/video42

## SRT and gstreamer

* https://github.com/Haivision/srt/blob/master/docs/gstreamer.md
* https://srtlab.github.io/srt-cookbook/

## gstreamer and rtsp

working minimal example: https://github.com/Enne2/PyGObject-GstRtspServer/blob/master/rtsp-server.py

other maybe helpful links (for getting an existing pipeline streamed):

* https://stackoverflow.com/questions/52562499/is-it-possible-to-stream-an-existing-gstreamer-pipeline-through-gstrtspserver
* http://gstreamer-devel.966125.n4.nabble.com/Continuously-streaming-a-video-file-code-review-td4671364.html
* https://stackoverflow.com/questions/59858898/how-to-convert-a-video-on-disk-to-a-rtsp-stream
* http://gstreamer-devel.966125.n4.nabble.com/RTSP-Server-from-a-manually-created-and-linked-pipeline-td4680305.html
* http://gstreamer-devel.966125.n4.nabble.com/Using-C-API-based-pipelines-in-RTSP-server-without-quot-launch-quot-arg-td4680144.html
* RTSP on_media_configure and appsrc: https://github.com/GStreamer/gst-rtsp-server/blob/master/examples/test-appsrc.c
* Link two pipelines: http://gstreamer-devel.966125.n4.nabble.com/Two-pipelines-link-them-merge-them-easy-handling-td4686753.html

a "relay" between cameras and rtsp, in rust:

* https://github.com/thirtythreeforty/neolink

## gstreamer: from udp to rtsp

* http://trac.gateworks.com/wiki/Yocto/gstreamer/streaming

## HLS

or gstreamer's `hlssink(2)`, if we want to serve files via HTTP and kodi can
read/play .m3u8 playlist

# VLC
Note that you have to close VLC and open it again for new streaming as VLC leaves the connections
open (I spent hours figuring out why http based streaming doesn't work - `netstat -4 --ip` is nice
for debugging in that respect).

## RTP
### Source
The address has to be the address where the video should be streamed **to**. In the following
examples, a multicast address is used. It is either the IP address of the device receiving the video (unicast address) or a multicast address 
like 239.255.12.42 (multicast addresses are between 224.0.0.0 and 239.255.255.255, some of
them being reserved, 239.0.0.0 to 239.255.255.255 are Organization-Local Scope so they are
good candidates, see
https://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml).

    cvlc -vv --sout '#transcode{vcodec=h264,acodec=mpga,channels=2,vb=800,ab=128}:rtp{mux=ts,dst=239.255.12.42,sdp=sap,name="Geris Game"}' GerisGame.mp4
    cvlc -vv --sout '#transcode{vcodec=h264,acodec=mpga,ab=128,channels=2,samplerate=44100,scodec=none}:rtp{dst=239.255.12.42,port=5004,mux=ts,sap,name=Geris Game}' :no-sout-all :sout-keep GerisGame.mp4
    cvlc -vv --sout '#transcode{vcodec=h264,acodec=mpga,channels=2}:rtp{mux=ts,dst=239.255.12.42,sdp=sap,name="Videokamera"}' v4l2:///dev/video0 # long latency
    cvlc -vv --sout '#transcode{vcodec=h264,acodec=mpga,channels=2}:rtp{mux=ts,dst=239.255.12.42,sdp=sap,name="Desktop"}' screen:// # not convincing

### Player
    cvlc rtp://239.255.12.42


## RTSP
For VLC, RTSP means RTSP combined with RTP.

### Source
We assume that the video source computer has the external IP 192.168.1.54.
Instead of rtsp://192.168.1.54:8554/ we could also use rtsp://192.168.1.54:8554/mystream.sdp

    cvlc -vv --sout '#transcode{vcodec=h264,acodec=mpga,ab=128,channels=2,samplerate=44100,scodec=none}:rtp{sdp=rtsp://:8554/}' :no-sout-all :sout-keep GerisGame.mp4
    cvlc -vv --sout '#rtp{dst=239.255.12.42,port=1234,sdp=rtsp://192.168.1.54:8554/}' :no-sout-all :sout-keep GerisGame.mp4


### Player
The address needs to be the address of the source. Note the backslash at the end.

    vlc rtsp://192.168.1.54:8554/


## VLC Remarks
* Latency: The following options are said to reduce latency:

      --network-caching=150 --clock-jitter=0 --clock-synchro=0

* Duplicating a stream is nice for debugging:

      cvlc -vv --sout '#duplicate{dst=display,dst="transcode{vcodec=h264,acodec=mpga,channels=2,vb=800,ab=128}:rtp{mux=ts,dst=239.255.12.42,sdp=sap,name=Geris Game}"}' GerisGame.mp4
      cvlc rtp://239.255.12.42


## HTTP
The address at the source side has to be the external one of the local computer.

### Source (server)
    cvlc -vv --sout '#transcode{vcodec=mp4v,acodec=mpga,vb=800,ab=128}:standard{access=http,mux=ogg,dst=0.0.0.0:8080}' GerisGame.mp4

### Player (client)

    vlc http://192.168.1.54:8080


# Kodi
The player built into code knows at least the following streaming protocols: http, rtsp.

https://kodi.wiki/index.php?title=Internet_video_and_audio_streams


# Random other projects

* µstreamer: https://github.com/pikvm/ustreamer
* minimal-webrtc-gstreamer: https://git.aweirdimagination.net/perelman/minimal-webrtc-gstreamer