When placing Ogg Theora video files in your site using HTML5 <video> tags, you can optionally specify the width and height of the videos. But how do you find the width and height? Use the tool ogginfo:

$ ogginfo video.ogg

Festival is an interesting OpenSource project for converting text-to-speech in Linux environment. It has a commandline tool text2wave which converts, guess what, text to voice in wave format. Simple usage:

$ echo "Hello World" | text2wave > a.wav

Wave files are uncompressed, and occupy lot of space. To encode to Ogg Vorbis format:

$ oggenc a.wav

This will create a.ogg in the current directory.

recordmydesktop is a powerful screencasting commandline tool for Linux. To capture the screen:

$ recordmydesktop

Press Ctrl+C to quit capturing. The captured video will be encoded in Ogg Theora format and saved as out.ogv (if out.ogv exists, as out-1.ogv and so on). To save the file in another name, say myout.ogv:

$ recordmydesktop myout.ogv

There is also a GTK frontend for recordmydesktop. To launch it:

$ gtk-recordMyDesktop

To encode a video file for use in HTML5 video compatible browser (firefox 3.5 and above supports HTML5 video), use the command:

$ ffmpeg -i in.flv -vcodec libtheora -sameq \
   -acodec libvorbis -ac 2 -sameq out.ogg

Finally use it in your page:

<video src="out.ogg">
Your browser does not support HTML5 video.
</video>

Reference: HTML 5 <video> Tag.

To stream video content using Video View Portlet, I had to re-encode some videos to flv format. This is pretty simple in Linux:

$ mencoder -oac copy -ovc lavc -o out.flv in.avi

-oac means Output Audio Codec and -ovc means Output Video Codec. The various options for -oac:

The options for -ovc: