[Bibio]

when you are using your editing software to create the OSD for chapters and such are you working directly with the mp4?

most editing software these days can split your mp4 into sections or add 'metadata' index to tell the OSD where the 'chapters' are. ''''you can then save the whole project as'''' mp4 or mkv, etc.etc. once you have 'compiled' your mp4 or mkv with index and OSD then you just need to burn as 'data disc'. if your bluray/dvd player supports mp4/mkv playback then it will read the file from the disc. as long as everything is contained within the mp4 or mkv.

if your just doing this for yourself then no need to burn a disc and instead just put the 'compiled' mp4/mkv it on a thumb drive and plug into tv or bluray player usb port.

if you want to hand hard copies out to friends and family not knowing what hardware they have the yes you need to burn as 'dvd' if not then burn the compiled mp4 or mkv as 'data disc'.

as long as the finished product contains all the chapters and OSD it matters not what the 'container' (mp4 or mkv) is as long as that container supports playback of chapters etc.etc

its the converting to 'DVD' that is taking up the space as its decompiling the mp4 to 'raw'.

its the same as burning a CD using mp3's even though the mp3 is 1.2mb when its converted into 'WMA' it will be 10 times the size depending on the original mp3 bit size.