Building a Raspberry Pi 2 WebRTC camera

如果网络条件允许，建议看原文。原文地址：http://www.rs-online.com/designspark/electronics/blog/building-a-raspberry-pi-2-webrtc-camera



Using Janus and gStreamer to feed video straight into the browser.

WebRTC enables browser-based Real Time Communications (RTC) via simple APIs. It is royalty free and powerful. We can use Janus, a general purpose WebRTC gateway,
to stream video from a Raspberry Pi directly to browsers, without having to install any extra software on client machines.

We will use a gStreamer pipeline to take the video output from a Raspberry Pi camera module and encode the video in H.264 format before passing it on to Janus.

Hardware used:

Raspberry Pi 2
USB Wifi adaptor
8GB micro SD card
Raspberry Pi Camera

Initial Raspberry Pi setup

To begin with we will assume that:

you are running the latest version of Raspbian (version 'January 2015' at time of writing).
you have a Raspberry Pi camera module attached.
the network is configured and you can SSH into the Pi.

First we will enable the Pi camera module:

$ sudo raspi-config
Choose 'Enable Camera' and press return
Save and quit raspi-config

Testing the camera

Now that we have enabled the camera module we can test that it is working correctly using the command line tool raspistill.

$ raspistill -o test.jpg

This should have taken a photo. Type ls to see if test.jpg has appeared in your directory.

Copy this photo over to your local machine and open it with an image viewer. If it needs rotating you can use the options -vf and -hf for vertical and horizontal flipping when taking the photo. E.g:

$ raspistill -vf -hf -o test2.jpg

Once you are happy the camera is working and you know which extra options to use we can move on to getting the camera streaming video over the network.

Setting up Janus

It is worth taking a look at the Janus GitHub repository for some background information and to assist with installation.

First make sure your Apt cache is up to date:

$ sudo aptitude update

Next we need to install build dependencies as follows:

$ sudo aptitude install libmicrohttpd-dev libjansson-dev libnice-dev libssl-dev libsrtp-dev libsofia-sip-ua-dev libglib2.0-dev libopus-dev libogg-dev libini-config-dev libcollection-dev pkg-config gengetopt libtool automake dh-autoreconf

We will not be making use of Data Channels, WebSockets or RabbitMQ so we don't need to install the optional dependencies.

Next we can clone the repository onto the Pi, build and install:

$ git clone https://github.com/meetecho/janus-gateway.git
$ cd janus-gateway

$ sh autogen.sh

$ ./configure --disable-websockets --disable-data-channels --disable-rabbitmq --disable-docs --prefix=/opt/janus

$ make

$ sudo make install

Now run a comand to install default configuration files:

$ sudo make configs

Next modify /opt/janus/etc/janus/janus.plugin.streaming.cfg (we will use nano but you may use an editor of your choice):

$ sudo nano janus.plugin.streaming.cfg

Add the following lines (and comment out the other example streams by adding a semicolon before each line)

[gst-rpwc]

type = rtp

id = 1

description = RPWC H264 test streaming

audio = no

video = yes

videoport = 8004

videopt = 96

videortpmap = H264/90000

videofmtp = profile-level-id=42e028\;packetization-mode=1



Save and exit the editor.

Installing gStreamer and Nginx

gStreamer is a pipeline-based multimedia framework that we will use to encode the video for streaming. To install gstreamer:

$ sudo aptitude install gstreamer1.0

Nginx is a lightweight web server that we will use to serve the Janus demos, specifically the streaming example. To install this:

$ sudo aptitude install nginx

Now copy the Janus HTML content to the Nginx server root:

$ sudo cp -r /opt/janus/share/janus/demos/ /usr/share/nginx/www/

Now start Nginx:

$ sudo service nginx start

Streaming test

Now open two SSH shell sessions logged into the Pi. We will run one command in each shell.

In the first shell execute the following:

$ raspivid --verbose --nopreview -hf -vf --width 640 --height 480 --framerate 15 --bitrate 1000000 --profile baseline --timeout 0 -o - | gst-launch-1.0 -v fdsrc ! h264parse ! rtph264pay config-interval=1 pt=96 ! udpsink host=127.0.0.1 port=8004

This will take video from the camera, format it and pipe it into gStreamer to be H.264 encoded, before sending it on to Janus.

In the second shell navigate to /opt/janus/bin/ and execute:

$ ./janus -F /opt/janus/etc/janus/

This starts the Janus WebRTC gateway.

On a different computer connected to the same network, ensure you running a recent version of Firefox (we are using build 37). Enter the following into the address bar:
http://<IP_of_your_pi>/streamingtest.html
This will load the streaming demo that is bundled with Janus. Click the 'Start' button next to the heading, choose your stream and click 'Watch or Listen' to display the video stream from the Pi directly into your browser!