Apologize for jumping in and a bit off topic from the OP question, but my experience here may be of interest.
Among many other trials and errors, I ran the following tests:
I ran FCPX 10.2.2 and created a 24 second QT .mov, 1280 x 720, 60p, ProRes 422 in two versions - one with an embedded audio track (W/A) and then the same video file without audio (W/O-A). The audio was a song off iTunes, m4A, 44.1 KHz.
I exported those with default settings.
I attempted to make a disk image with iDVD 7.1.2 of both of these using the "Sunflower" theme.
Results as follows:
With my 27" late 2012 iMac running OS X 10.10.5 the W/A movie encoded and multiplexed successfully and gave a disk image that could be opened and played.
The same setup, and the W/O-A got an encoding error and stopped. Totally repeatable.
I booted up the iMac from a previously cloned backup drive with 10.10.4 running.
Both movies, with and without audio, encoded and played successfully.
To make a long story short, I've run a number of other tests along these lines, lots of variations, and 10.10.4 has no problems but for me iDVD under 10.10.5 will not encode a video file without an audio track.
I believe something has changed in the OS and that it's not an FCP X or iDVD issue.