CODEWITHSUNDEEP
javaopencvwebrtc
Gildraths
Gildraths

Reputation: 376

How to get OpenCV WebRTC Stream into Java

We are currently working on a robotics project where we want to recognize elements with OpenCV. The detection already works in OpenCV with a video.

For the hardware we use a Raspberry Pi B2 with a Raspicam. After long search for something with minimal lag we found http://www.linux-projects.org/modules/sections/index.php?op=viewarticle&artid=14

The WebRTC solution is by far the one with the lowest lag 200-300ms. Now we wish to open the WebRTC Stream in Java, however we weren't able so far.

Any pointers how we can open a WebRTC Stream in OpenCV in Java?

Upvotes: 2

Views: 1856

Answers (2)

Gildraths
Gildraths

Reputation: 376

For anybody interested here how we were able to connect OpenCV over a h264 stream with a delay of 200-300ms over WLAN:

  1. Create a WLAN Hotspot with a nano wlan-adapter:
    We used a Edimax EW-7811Un

Follow the tutorial at:
http://www.daveconroy.com/turn-your-raspberry-pi-into-a-wifi-hotspot-with-edimax-nano-usb-ew-7811un-rtl8188cus-chipset/

  1. Install uv4l on the raspberry pi:

    $ curl http://www.linux-projects.org/listing/uv4l_repo/lrkey.asc | sudo apt-key add -

Add the following line to the file /etc/apt/sources.list :

deb http://www.linux-projects.org/listing/uv4l_repo/raspbian/ wheezy main

$ sudo apt-get update
$ sudo apt-get install uv4l uv4l-raspicam

Detailed instruction and documentation here: http://www.linux-projects.org/modules/sections/index.php?op=viewarticle&artid=14

  1. Install OpenCV 3.0 auf Windows computer:

We were using OpenCV installed in ecplise according to this tutorial: http://docs.opencv.org/3.0-beta/doc/tutorials/introduction/java_eclipse/java_eclipse.html

  1. Run the server on the raspberry pi:
    Either install the uv4l-server according to the linux-projects website or per command line:
    uv4l --auto-video_nr --driver raspicam --width 640 --height 480 --encoding h264 --server-option '--port=8080'

  2. connect to the stream:

    System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
    Mat image=new Mat();
    VideoCapture capture = new VideoCapture();
    capture.open("http://IPADDRESSofRaspberry:8080/stream/video.h264");
    capture.read(image);

Important hints and potential errors:

Check the documentation of uv4l for speeds and resolution. We went with 640x480 @ 30fps.
If you want to check if the stream is loading you can open it in VLC mediaplayer, however make sure to set the correct demuxer: http://www.stardot-tech.com/kb/index.php?View=entry&EntryID=186

Upvotes: 1

gogasca
gogasca

Reputation: 10048

Have you take a look at this one: http://www.rs-online.com/designspark/electronics/blog/building-a-raspberry-pi-2-webrtc-camera

Other option is to use a central MCU (check Medooze/McuWeb project) the idea is to connect your Raspberry via Websockets/SIP. This stream will be mixed into the MCU and then you can generate an additional stream back to any server (Example: Wooza) where you can apply OpenVC. Why do you need Java?

Upvotes: 0

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