If anyone is looking for a working G4TV code, here it is...
(tested with AllVideos v2.5.3, include this in your plugins/content/jw_allvideos/jw_allvideos_sources.php and use it with something like {g4tv}27897{/g4tv} in an article)
"g4tv" => "
<span style=\"width:{VWIDTH}px;height:{VHEIGHT}px;\" class=\"allvideos_player\" title=\"JoomlaWorks AllVideos Player\">
<object width=\"{VWIDTH}\" height=\"{VHEIGHT}\" id=\"VideoPlayer\">
<param name=\"movie\" value=\"http://www.g4tv.com/sv3/{AVSOURCE}\" />
<param name=\"allowScriptAccess\" value=\"always\" />
<param name=\"allowFullScreen\" value=\"true\" />
<embed src=\"http://www.g4tv.com/sv3/{AVSOURCE}\" type=\"application/x-shockwave-flash\" name=\"VideoPlayer\" width=\"{VWIDTH}\" height=\"{VHEIGHT}\" allowScriptAccess=\"always\" allowFullScreen=\"true\" />
</object>
</span>
",