If Zencoder reports a failure on postback (say due to a corrupt input file) the theme function 'theme_video_conversion_failed' is not called, and the rules event 'video encoding failed' also does not fire..... so the user is given no indication of the problem. The node view continues to display 'This video is currently being processed. Please wait.' - which will leave them waiting a very long time.... ;)
We have the transcoder error in the log - but unless someone is actually monitoring this - it's of little use.
Zencoder reports errors in postback for fid 3509, job id 31930560: The input file appears to be corrupt and could not be correctly decoded.