KDE spellchecker not working for Indian Languages

As I mentioned in my blog post on Language detection the sonnet spellchecker of KDE is not working. I read the code of the Sonnet and found that it fails to determine the word boundaries in a sentence (or string buffer) and passes the parts of the words to backend spellcheckers like aspell or hunspell. And eventually we get all words wrong. This is the logic used in Sonnet to recognize the word boundaries

Loop through the chars of the word, until the current char is not a letter/ anymore.

And for this , it use the QChar::.isLetter() function. This functions fails for Matra signs of our languages.

A screenshot from a text area in Konqueror:

For example

#include <QtCore/QString>
#include <stdlib.h>
int main(){
	QChar letter ;
	letter = 'அ';
	fprintf(stdout,"%d\n", letter.isLetter());
	letter = 'ी';
	fprintf(stdout,"%d\n", letter.isLetter());

In this program, you will get true as output for அ and false for ी.

When I showed this to Sayamindu during foss.in , he showed me a bug in glibc . Eventhough the bug is about Bengali, it is applicable for all languages. It is assigned to Pravin Satpute and he told me that he got a solution and will be submitting soon to glibc.

But I am wondering why this bug in KDE unnoticed so far? Nobody used spellcheck for Indian languages in KDE?!

Let me explain why this is not happening in GNOME spellchecker if this is a glibc bug. In gnome, this word splitting will be done in application itself using gtk_text_iter_* and these iteration through words are done by pango words boundary detection algorithms.

Filed a bug in KDE to track it.

Youtube to MPEG or Ogg video conversion

Here is the two line method to convert a youtube video to oggvorbis video.
Locate clive and ffmpeg2theora in your package and install
$clive http://in.youtube.com/watch?v=6JeZ5oeAEyU (replace this with the youtube address you want)
It will create a flv file.
Convert to mpeg video file
$ffmpeg -i AmericaAmerica.flv AmericaAmerica.mpg
Convert to ogg video file
$ffmpeg2theora AmericaAmerica.mpg (replace it with the name of the flv file the previous command created)
Done. You can see the .ogg file in the directory from where you executed the above commands

Dhvani 0.94 Released

A new version of Dhvani -The Indian Language Text to Speech System is available now. The new version comes with the following improvements/features

Dhvani documentation is available here.

Binary packages and source code are available here


  • Rahul Bhalerao for Marathi module and patches
  • Zabeehkhan for Pashto Module
  • Nirupama, CDAC Chennai and CDAC Noida people for testing and reporting bugs
  • NRCFOSS Chennai, Krishnakanth Mane and many others for feedbacks
  • Amida Simputer team for patches on Telugu module especially the Telugu number reading logic
  • Debayan and Roshan for testing and informing problems

There was good amount of code change in this version. Still there are many improvements to do in language modules and synthesizer. Some of the language modules requires developers who speak that language. Syntheziser got some improvements and require some amount of research to make the speech more natural. So your feedbacks, suggestions, bug reports and patches are valuable.

PS: A note for quick usage after installation from binary: After installing deb or rpm, Open gedit, edit->preferences->plugins, enable external tools. Dhvani will be available as a plugin there. Select some text in any of the supporting languages and click the Dhvani menu.

Language Detection and Spellcheckers

A few weeks back there was a discussion on #indlinux IRC channel about automatic language detection. The idea is, spellcheckers or any language tools should not ask the users to select a language. Instead, they should detect the language automatically. The idea is not new. There is a KDE bug hereand Ubuntu has this as an brainstorm idea. It seems M$ word already have this.

A sample use case can be this: “While preparing a document in Openoffice, I want to write in English as well as in Hindi. For doing spellcheck, I need to manually change the language rather than the application detect it automatically”

Regarding the algorithm behind automatic language detection, there are many approaches. Statistical approaches are effective for languages sharing same script(For eg: languages which use latin script or Hindi and Marathi). N-gram based methods are used in statistical approach. Here is a ‘patented’ idea . And this page explains a character trigram approach. Google has a language detection service(http://www.google.com/uds/samples/language/detect.html) and it seems it is still in development or ‘learning stage’.

Here is an example of statistical language detection: languid(It did not work for me when I tried, But you can download the source code and check)

Sonnet is the spellchecker framework of KDE written by J. Rideout. It is also trying to provide the language detection feature. Here is an old article in linux.com about that. It is based on n-gram based text categorization and is a port of languid. From the article:

A gram is a segment of text made of N number of characters. Sonnet uses trigrams, made from three characters. By analyzing the popularity of any given trigram within a text, one may make assumptions about the language the text is written in. Rideout gives an example: “The top trigram for our English model is ‘_th’ and for Spanish ‘_de’. Therefore, if the text contains many words that start with ‘th’ and no words that start with ‘de,’ it is more likely the text is in English [than Spanish]. Additionally, there are several optimizations which include only checking the language against languages with similar scripts and some heuristics that use the language of neighboring text as a hint.”

(I tried sonnet and could not get it working for ml_IN. Instead of words, it was iterating through letters. Anyway I will check this problem later.)

As far as Indian languages are concerned, Unicode code range based language detection will work for most of the cases. Most of the languages has its own script and Unicode code point range. For example, detecting Malayalam is a matter of checking the letters are in the Malayalam Unicode range. But for Devanagari script it is not straight forward. Hindi , Marathi etc use Devanagari script. Dhvani, the text to speech system for Indian languages use a simple algorithm for language detection(http://dhvani.sourceforge.net/doc/language-detection.html). There the Hindi and Marathi is identified by giving a priority for LANG environment variable. But it will fail if somebody try to use Marathi in an English desktop(Users can specify the language to be used – In that case language detection will not be done.).

In the case of spell checkers other than LANG environment variable there are other options. When you type in gedit or any text editors, detecting the keyboard layout will be one way of detecting the language. But it depends which IME the users uses. It can be xkb or scim or even a copy-paste.

Anyway, it is pretty clear that the current natural language features in the free desktops requires more improvements. Based on a discussion we had in #indlinux IRC, we had setup a wiki page here to discuss on this.

As a proof of concept, I tried to write a spellchecker for Gedit texteditor with language detection for Indian languages. Basically it uses Unicode character range. It is a gedit plugin written in python. And it uses pyenchant spellcheck wrapper library. Install python-enchant using your package manager if it is not already installed. Download the plugin and python module to ~/.gnome2/gedit/plugins folder and restart gedit. Enable external tools and new Spellchecker plugin in edit->preferences->plugins. It does not have the pango error style underline or suggestions in context menu as of now. It just prints the results and suggestions in the console of gedit. And ‘Add to Dictionary’ etc are not there now.

I would like to request interested developers to come forward and make this feature ready to use in free desktops. Suggestions are welcome. We need good algorithms for detecting the language too.
A sample use case: “System locale is English and I am typing a document in Hindi and want to write some Marathi sentences in between. Without manually changing the language, system detect the language of each word and check the spelling against corresponding dictionaries.”

PS: Because of the inflectional and agglutinative nature of some of the Indian languages, the spell checking is not at all effective. I will write on that later.

Gedit plugin for showing unicode codepoints

While working with Unicode text, it is often required to get the Unicode code points of text for debugging. Using python, it is very easy to get the unicode codepoints of the text. Following examples illustrates it.

>>> "സന്തോഷ്".decode("utf-8")


>>> str=u"സന്തോഷ്"
>>> print repr(str)

Well, But we need to take python console and type/paste the text etc..How can we make it more easy? What if pressing F12 key after selecting some text gives the codepoints?
So I wrote a plugin for gedit. I never knew that writing a gedit plugin is too easy. This tutorial gives all the required information.
Download the plugin file and python module and place it in .gnome2/gedit/plugins folder inside your home folder. And restart gedit. Enable the plugin from Edit->Preferences->Plugins menu. Note that you need to enable the External tools plugin too.

Select some text and press F12. If text is not selected, entire content of the document will be used.