doing as described here http://tagavalgal.blogspot.com/2011/11/quicktime-demuxer-not-found-in-ubuntu.html as someone mentioned in another bug report has solved this problem for most but not all of my videos. they will all play with the command $gst-launch playbin uri=file:'<file>'
doing as described here http:// tagavalgal. blogspot. com/2011/ 11/quicktime- demuxer- not-found- in-ubuntu. html as someone mentioned in another bug report has solved this problem for most but not all of my videos. they will all play with the command $gst-launch playbin uri=file:'<file>'