M4v files

To get a disc that will play on a DVD player one must use a video DVD authoring application to create and burn the disc.

Since iDVD has been discontinued and unsupported for over 5 years you can get a DVD authoring application from the App Store. Since you're only using video files for the video DVD project any of the apps will do the job.

There is one app, DVD Maker Lite - DVD Creator, that can also create slideshows from still photos like iDVD did. The free demo version at the App Store will put a water mark over the slideshow but you can create a disk image and play with DVD Player to see how it works.

Follow this workflow to help assure the best qualty video DVD:

Once you have the project as you want it save it as a disk image via the File ➙ Save as Disk Image menu option. This will separate the encoding process from the burn process.

To check the encoding mount the disk image, launch DVD Player and play it. If it plays OK with DVD Player the encoding is good.

Then burn to disk with Disk Utility or Toast at the slowest speed available (2x-4x) to assure the best burn quality. Always use top quality media: Verbatim, Maxell or Taiyo Yuden DVD-R are the most recommended in these forums.

Any chance Apple will provide an updated IDVD that will generate a useable file?

From zero to none. It's a dead horse.

I just created a test project withd DVD Maker Lite-DVD and a .m4v movie file and it saved to an .iso disk without a problem.

You can open the .m4v file with Quicktime Player and export it as a 480p (.mov) file and use that.