Re-authoring a DVD with both 4:3 and 16:9 parts

[lordretsudo]

Looking for some help with quite a complicated problem here... I have added a scene from a 4:3 VHS rip back into a 16:9 DVD using Sony Vegas. I've reset the IFOs to 16:9, but the film seems to display in 4:3... is there any way to correct this, or a better way to re-author the DVD that will keep the 16:9 flagging intact?

Any advice would be great!

[Ghitulescu]

Well, each TitleSet should have one DAR and only one, either 4:3 or 16:9. Mixing both within a single VTS makes the DVD illegal (out of specs).
You don't need to modify the IFO, if the player understands and respects the DAR within the MPEG header, it'll switch automatically 4:3<->16:9. Generaly the standalone DVD recorders allow this as the only measure that circumvents the recording of movies with commercials (16:9 movies vs. 4:3 ads), this works normally only in the recorder that made it.
However most authoring software do not allow the mixing, so you might need to trick them wuth DVDpatcher.
If you reencode the 4:3 files to 16:9 (pillarbox) or viceversa (letterbox) you'll end with a legal DVD.

[bigotti5]

You don't need to modify the IFO,

From the specs a DVD Video player has to read DAR from IFO only.