muxman error

[vanderbog]

Hi guys,
I am converting an avi to DVD elementary streams, to add a subtitle.
I do the convertion with Canopus. When trying to multiplex all together with Muxman...I get an error related to GOP not being null or something like that (see the picture).
What does this mean ? What setting I need to take care of in Canopus, to avoid this nighmare ?
Thanks.

[AlanHK]

Muxman is very fussy about files following standards exactly. Often it complains or rejects files other authoring apps deal with fine and work in practice despite being out of spec.

Your error appears to be having too many pictures in the GOP, which may be a side-effect of doing pulldown. I don't use Canopus so I can't say how to change that; but try Rejig, which has a similar authoring module, it may be able to use your files as-is.

[vanderbog]

Thanks for your reply.
Yes, it's very fussy indeed. Rejig was useless. I just tried Ifoedit and it worked but for some reason it messed the image quality
Frustrating

[manono]

Maybe you shouldn't complain, since you set up the encoding incorrectly. Go back and redo it, this time setting your GOP length for 12 frames before Pulldown.

Muxman isn't being fussy, just following specs.

[vanderbog]

Thanks Manono ! I'll try that. I didn't know.
But what does it mean "before pulldown" ?

[manono]

But what does it mean "before pulldown" ?

AlanHK speculated, and I agree, that the easiest way to wind up with the GOP size too large is to encode for 23.976fps. Most encoders have the GOP length set for 15 frames (30 fields) by default, and if creating an NTSC DVD, 23.976fps has to have pulldown applied in order to output 29.97fps. This increases the GOP length by 25% (29.97/23.976=1.25). 15 frames=30 fields. 30 x 1.25=37.25. So, some GOP lengths will be as great as 38 fields (19 frames), or 2 fields greater than that allowed by the NTSC specs, and would explain the error message.

If you encode for 23.976fps, no authoring app will accept the output until after it's had 2:3 (or 3:2) pulldown applied. You can (usually) do it during the encoding, or afterwards. One popular after-encoding app used to apply pulldown is DGPulldown at default settings. If you're encoding 23.976fps for NTSC DVD, you'd best set the GOP size to 12 frames (24 fields) to allow for the GOP size increase (to 15 frames or 30 fields) after pulldown. For more on pulldown:

http://en.wikipedia.org/wiki/Telecine#Common_pulldown_patterns
http://www.dvdfile.com/news/special_report/production_a_z/3_2_pulldown.htm

If you're not encoding for 23.976fps, then something else caused the screwup.

[vanderbog]

Thanks a lot for the detailed explanation, Manono.
Indeed, I changed the GOP size to 12 and it's good now, Muxman complains no more .
Thanks again. All the best.