Video Editing Forums: Digital Director - View Single Post - Exporting Mpeg-2 Video file from Premier Pro 1.5

Crusty · #6 (**permalink**) 01-04-2006, 05:48 AM

Re: Chapter jumps - I think a small fade in is fine, though 90 frames (3 seconds) might be a bit long. An abrupt snap is a bit jarring and it may detract from the subject matter.

Re: lead-in copyright.. I really don't know if NeroVision can do this. I've never tried it. One thing I'm sure you can do is put in a video clip for the background on the main menu. This isn't elegant, but it would let you get the notice out there at the start. This video clip will get looped, so provide a good length after the copyright notice to keep it from flashing again and again.

In the structure of NeroVision DVD menus, each video segment is called a 'title'. Each title has it's own mpeg file. Each title can also have chapters. If you have multiple titles, each one gets a selection button/window on the main menu (and extra main menu pages are possible it you have a lot of titles). When the user selects a title, if it has no chapters the title starts playing else there's a jump to a chapter menu for the title with the first chapter highlighted. Pressing play starts the title.

More professional types of DVD authoring programs would let you have a start title that always plays when the DVD is inserted, then when that is finished allow a jump to another title or menu.

Re: GoP - Group of Pictures. MPEG compression is a mixed bag of tricks that are used when needed. The first trick is called an I frame. This is single image compressed with a good method. It stands by itself and needs no other frames in order to be decompressed and output to the TV. The next trick is a P frame. It uses a Previous frame and it's own information to reconstruct the output frame. It's about half the data of an I frame. The last trick is a B frame, it uses a Previous and the next frame to reconstruct the current frame for output. It uses about a quarter of the data of an I frame.

These sorts of frames are strung together to make the video stream. A GoP is a group of an I frame and all the P and B frames up to the next I frame. There is a selectable repeating pattern, usually something like IBBPBBPBBPBBPBB that's common, but it's not cast in stone and can change according to scene complexity, a fast pan/zoom/jump can result in more I frames at the cost of larger data size. This is up to the encoder settings more than anything. Real Hollywood style MPEG artists will manually adjust these parameters for every action scene to minimize distortion resulting in superb videos. We poor humans are usually dependant on the default encoder settings. If one has a lot of time these settings can be fun to diddle with to see the effects.

Anyway, a chapter or a fast forward/backwards jump can only be from I frame to I frame, otherwise the intervening frames would have to be decompressed to calculate the output picture and that takes time and memory. The GoP setting mostly influences how 'coarse' the jump resolution can be. A GoP of 6 would result in IBBPBB groupings that would allow relatively fine steps, about a sixth of a second. GoP of 15 allows about half second steps. If you select a B or P frame to start a chapter, at transcode time NeroVision will find the GoP it's in and then decompress all it's frames then make I frames out of them so the jump will be smooth.