Exclude certain nodes from the 'ironing'

My manifest (http://54.241.9.147//new-fandor/vod/40/4032/captain_video_FILM_v14_chromecast.smil/manifest_mpm4sav_mvlist.mpd) fails to load within the 10 seconds that my Android sender requires.  I get a timeout and the video won't play.  I have very little idea on what's actually going on in the ironing code other than it seems to be merging certain properties down the manifest's json tree.  I'm not sure why that's required.  My manifest has a ton of segments(it's over 4 hours), so I stopped doing some of the work at the Segment level.  I'm not sure if this breaks anything, but it puts the parsing performance under 10 seconds and the video starts playing without a timeout.  

I would love to understand what's going on here so I could possibly improve the code further.