Mjpeg carrier... how to use?

[lukeboorman]

Hi. We would like to compress the iCub image streams using the Mjpeg carrier in YARP but are struggling to use this. We will stream the camera output to a remote location and so need to reduce bandwidth usage. Is there an example on how to do this?

I have turned on the mjpeg carrier in YARP cmake and have the autocompress on, is there a setting we are missing in the icubmoddev frame grabber? The Mjpeg_test executable I assume only decompresses the stream?

I have started using the mjpegstream c++ class, but the include file isn't moved across with the yarp install and I assume I don't need to use this?

Ps How do I add labels #Discussion #Software

[drdanz]

Hello @lukeboorman, the mjpeg_carrier must be compiled in order to work, please check that the ENABLE_yarpcar_mjpeg_carrier flag is enabled when building yarp on both sides.

The easiest way to use the mjpeg carrier is this on the same pc/network:

(shell 0) yarp server
(shell 1) yarpdev --device test_grabber --name /grabber
(shell 2) yarpview --name /view
(shell 3) yarp connect /grabber /view mjpeg

Another way to use it, is to connect a stream generated by yarp to an external application

(pc1) yarpdev --device test_grabber --name /grabber # yarpserver must be running
   # get the ip address and port from the output (here I'm assuming 192.168.99.1:10002)
(pc2) open browser at http://192.168.99.1:10002/?action=stream

To connect 2 different yarp ports running on different networks, you should be able to do something like this:

(pc1) yarpdev --device test_grabber --name /grabber # yarpserver must be running
   # get the ip address and port from the output (here I'm assuming 192.168.99.1:10002)
(pc2) yarpview --name /view # yarpserver must be running, but not necessarily the same instance
(pc2) yarp connect http://192.168.99.1:10002 /view mjpeg

Finally the mjpeg carrier allows you to connect to any external mjpeg stream you can reach, you will have to do something like this (to be honest I never tried it and I was not able to do it right now, perhaps @apaikan can add something):

yarp name register /streamer tcp ... 8080
yarpview /view
yarp connect /view /streamer mjpeg # Note that the connect order because this is a "pull" protocol

[lukeboorman]

Thanks for the info, will give the test_grabber a go today.

[apaikan]

@lukeboorman the instruction provided by @drdanz should work.
The mjpeg carrier automatically compress and decompress the images and you do not need to implement anything to get it work. If you have compiled Yarp with ENABLE_yarpcar_mjpeg_carrier=ON, it is enough to connect two yarp ports using the mjpeg carrier:

yarp connect /sender /receiver mjpeg

mjpeg carrier also allows you to stream out Yarp images and visualize them using any standard application (e.g., mplayer, firefox). For example to see a Yarp image from a web browser (can be a browser from your mobile phone too) follow these steps:

• run a test_grabber

$ yarpdev --device test_grabber 
[INFO]Test grabber period 0.0333333 / freq 30 , mode [line]
[INFO]created device <test_grabber>. See C++ class yarp::dev::TestFrameGrabber for documentation.
yarp: Port /grabber active at tcp://10.1.89.119:10002
yarp: No framerate specified, polling the device
[INFO]created wrapper <grabber>. See C++ class yarp::dev::ServerFrameGrabber for documentation.
yarp: Port /test_grabber/quit active at tcp://10.1.89.119:10003
[INFO]device active...
[INFO]device active...

• open a firefox/iceweasel browser (chrome does not support mjpeg streaming) and enter the ip address of the test_grabber in this format:

http://10.1.89.119:10002/?action=stream

Let me know if you encounter any problem.

P.S. You can read more on that here : http://apaikan.net/papers/Fitzpatrick14middleway.pdf

[lukeboorman]

Thanks we have got this working between the icub laptop and another ubuntu pc uisng yarpview.... "yarp connect /icub/cam/left /yarpImgView mjpeg". Reading the paper now...

However we are having some issues:

1. I can't get this to run on a windows machine (probably my config!), Running the yarp connect... it finds the mjpeg carrier, but says "yarp: Failed to find library support for carrier mjpeg". The PC has yarp_data_dirs etc setup and the mjpeg_carrier.dll have been produced and is in the 'install' location.

Other comments:

1. When closing the connection we have to use "yarp disconnect /icub/cam/left mjpeg://yarpImgView" otherwise it says the connection doesn't exist.
2. On connecting the return message from yarp seems to be the wrong way round (to -> from), or is this a two-way link? "Success: Added connection from /yarpImgView mjpeg://icub/cam/left

Thanks again for the help

[drdanz]

There are some issues on windows, I managed to get it working, but I don't remember exactly what I had to change, and also it works only in some cases, I will investigate this a little bit more and try to fix it...

[Tobias-Fischer]

Hi @lukeboorman,
I can only help with your "other comment" 2: See the comment from @drdanz, where it is written that mjpeg is a pull protocol. Therefore, sender and receiver are the wrong way around. Did you try the same trick with other comment 1?

[pattacini]

@lukeboorman any update?

[lukeboorman]

Hi, thanks all! We got MJPEG stream running and used gateways to send the data over a different network. Much increase in frame rate and we were able to increase the resolution using Mjpeg with bayer, which overcomes some of the visible effects of the compression. I still struggle to run on my windows without running from within the yarp build directory, I think I have all the environment variables set up correctly.

[pattacini]

... hence it should suffice to have yarp/build/bin/release in the path, right?