Lumix GH3 to iDVD - black stage curtain is a macro block mess

[sigamy]

I am creating DVDs for my child's elementary school. I shot ceremony in the gym/auditorm with teachers speaking at podium in front of a black stage curtain. On the final DVD the black curtain is a mess of dancing macro blocks.

Shot with GH3 in MOV format, 72Mbps. I'm editing in iMovie. Footage looks fine in iMovie. I have exported as 1080p from iMovie. After creating a DVD with iDVD, the black curtain is basically a big macro block.

I know I'm using consumer tools but I can't understand why these black curtains are getting so crushed. The rest of the frame looks fine--teacher at podium, students, etc.

Is there anything I can do to get a better encode? Would compressor do a better job?

 

[Andrius Simutis]

What are you exporting out of iMovie? If it's a compressed codec, like h264, and then you're bringing that into iDVD to compress again into MPEG2 you will see all sorts of compression artifacts. If you export a ProRes422 out of iMovie, or go direct to MPEG2 out of iMovie then you should see an improvement over what you've been getting.
Compressor might help, but only if you're giving it a good uncompressed signal coming in and know what settings are the right ones.