Saturday, December 19, 2015

Use your DSLR Camera as a Webcam on Ubuntu

It is not uncommon that you have a DSLR and you wonder that it would be awesome if you can use it as a webcam. Have video calls with your family and friends using your high definition DSLR camera. Recording videos directly from your DSLR camera into your computer or us it for live view.

I was trying to do the same thing and searched over the internet, found some software that can do that but are not free and/or won't work on my Linux machine.

But recently found another way of achieving it. Basically making my DSLR work as a capture device, that is /dev/video*.

To do that you need a utility named gphoto2. First you have to check whether your camera is in the supported list of cameras, For that go through the list of supported cameras here.

I have a Canon EOS 100D, which is in the list, so it works for me.

Now attach your camera with your machine using the USB cable, and execute the following command in the terminal (linux shell).

gphoto2 --abilities

This should show you the camera name and abilities and other information, this shows that your camera is detected.

Now to the next step,

You need "v4l2loopback kernel module" to make a virtual device in /dev/video* for your camera. This can be installed by executing the following command,

sudo apt-get install v4l2loopback-utils

If all goes without any error, you can execute the following command to make a virtual camera device for your DSLR connect to the machine.

modprobe v4l2loopback

gphoto2 --capture-movie --stdout | gst-launch-0.10 videotestsrc ! v4l2sink device=/dev/video1

Now you can use this new device /dev/video1 as your webcam.

For Example you can configure Skype to use this as a Video device for video calls.

Monday, November 30, 2015

Fix Urdu font rendering in Chrome in ubuntu 14.04

You might have faced a problem in Ubuntu using chrome when you visit a website that has text in Urdu and it doesn't render properly. Mostly the letter "Ří" is not rendered and connected correctly with other letters.

Now font rendering is a very complex process which involves (but not limited to) positioning (pen algorithm), layout and Bidirectional text processing. The problem mentioned above is related to layout and seems like some layout information in the font being used is wrong or missing.

Now this is very annoying and becomes very difficult, and sometimes you even feel like that you are deciphering an encoded text by analysing the broken Urdu text.

This can be easily fixed by first installing a proper Urdu font by executing the following command,

sudo apt-get install fonts-nafees

After installing this you have to change the standard font in your browser. Ubuntu by default uses the font "Abyssinica SIL".

To change the font go to Chrome settings, in settings search field search for "Web Content" and client on "Customize Fonts".

Now change the Standard font to "Nafees". This  should correct the rendering of Urdu text in chrome.

This problem only occurs in the websites which do not explicitly specify the font that they want to use.