xawtv
xawtv was originally just a TV viewing application for Bttv devices (bt848, bt878), written by Gerd Knorr, but evolved into a small suite of X11 applications for V4L devices (the 3.9x branch). The version 4.x development branch added support for DVB functionality.
Unfortunately, development of both branches of xawtw, versions 3 and 4, came to a halt for several years. Having not kept in step with broader kernel developments, version 3 had become broken and most Linux distributions choosing to include it within their releases were stuck with having to independently provided their own patch solutions to xawtv version 3.95. It is doubtful that version 4 ever saw widespread packaging by distributions. In any regard, in 2010, an effort was made by LinuxTV developers to provide a centralized repository for both versions (see here and here for details).
xawtv 3.xx branch
The xawtv version 3.xx development repository can be found in the http://git.linuxtv.org/xawtv3.git tree.
Since becoming hosted on LinuxTV, there have been a number of changes made to this original xawtv branch that help to modernize it and allow it to act as a reference like V4L application. In time, it is hoped that Linux distributions will both submit changes to this version as well as utilize it as the one they package within their releases.
xawtv 4.xx branch
The xawtv version 4.xx development repository can be found in the http://git.linuxtv.org/xawtv4.git tree. This branch essentially remains in a state of stasis and awaits anyone so inclined and willing to pickup/resume its development.