DVD Architect Studio: Question 2

[Bobby]

Hey guys, making great progress. I have just finished my first project using DVDSA and I really like it. I had a LOT more flexibility in controlling my menus. Some things were a bit more work than I liked (such as setting where the scene markers are) but overall a good thing.

Question: Some of my scene markers show little orange triangle icons, and some are yellow with an exclamation point. I can't figure out what it is trying to tell me. When I prepared the DVD there were no error messages associated with them, and everything seemed to run fine.

Also, DVDSA created a scene marker for me at the beginning of the video, but won't let me rename or delete it. No problem as I just used the name as-is, but wondering why...

Does anybody know what the yellow means?

[RJ Johnston]

There are yellow in and out point markers, allowing you to trim clips on the timeline in DVDAS. Those yellow things?

Move the cursor to the beginning of 1. Scene/Chapter. Then type "M" to place another marker, which you can rename. It will become number 1, but as you move the orange marker to the right, it will become number 2 and reveal the original 1. Scene/Chapter label underneath.

I haven't seen any exclamation points yet, but when I do, I will let you know.

[Chuck Engels]

Sounds like an error of some kind Bobby. What happens if you click, double click, or right click on the yellow triangle with the exclamation point?

[RJ Johnston]

Okay, I had to use a magnifying glass to see that it was an exclamation point.

When dealing with MPEG files, if the scene marker is not on an "I-Frame" then you will get that symbol.

For DVD-compliant video files, markers must occur at I-frames. If a marker does not occur at an I-frame, the tag will appear. To snap the marker to the I-frame, drag the marker along the timeline to one of the I-frame reference points .

I-frame reference points will appear on the timeline once you begin to drag the marker.

When the marker has snapped to the I-frame, the tag will clear from the marker.

If a marker is not an I-frame, you can recompress the video title to add an I-frame at that location on the timeline. However, if you don't manually recompress the title, DVD Architect Studio will automatically move the marker to an I-frame. For more information on recompressing video titles, click here.

[Chuck Engels]

if the scene marker is not on an "I-Frame" then you will get that symbol.

Ahhh, that makes sense. Good find RJ, thanks

[Bobby]

Thanks Robert. That makes perfect sense.

Where did you find that info? I looked in the DVDSA .pdf document and couldn't find it. That .pdf document is not too detailed

[Bobby]

Just a final comment on my now completed project.

The fonts in the menus are beautiful - no excess anti-aliasing at all. So that leaves me to wonder why under PRE I was having so much trouble and why some of the others here weren't seeing it also.

I know that it is not corrupted font files as I am using the same fonts (Trajan Pro, etc.).

I am not going to worry about it, now that I have a "fix" and especially that the fix only cost this old retired guy $26!

[Steve Grisetti]

Yep. It's in there, Bobby. In a discussion of the Timeline panel.

It's also, of course, in my book. Not that that helps you right now!

[Bobby]

Oh, NOW you tell me

[RJ Johnston]

Thanks Robert. That makes perfect sense.

Where did you find that info? I looked in the DVDSA .pdf document and couldn't find it. That .pdf document is not too detailed

I pressed F1 and then did a Search for "Icons."

[Peru]

At the risk of sounding ignorant, what is an I-frame?

[Bobby]

I-frames:

At a high level, using i-frames is one form of compression. You start with a full frame, and then subsequent frames are not really full frames, but what is in the file (or data stream) is just the differences between the frames. That goes on for an unspecified number of frames - possibly 15 or so - determined by when you apply the MPEG compression. So you are saving a lot of space in the file by only keeping difference information.

This takes advantage of the fact that in 1/30 sec there is often not much change between frames.

But after a while keeping track of the changes is too much and so you stick in another full i-frame again, and start over.

DV-AVI files do not use this form of compression and that is why they are easier (i.e. less horsepower required) to edit. To edit an MPEG stream you have to re-create all the individual frames from the i-frame and that takes a lot more horsepower.

See http://en.wikipedia.org/wiki/Video_compression for an intro.

What the guys were saying above is that DVDSA does not allow you to hook a scene marker to a frame that is not an i-frame, as it isn't complete.

[Chuck Engels]

At the risk of sounding ignorant, what is an I-frame?

I think this part of an article explains it pretty well. If you ask what I Frames are then you also need to know what B frames and P frames are as well

Terminology in MPEG Compression
http://www.cs.wfu.edu/~burg/Courses/Spr ... s/MPEG.htm

There are three types of frames used in MPEG compression — I frames (intraframes), P frames (predicative frames), and B frames (bi-directional frames).

I frames are compressed without reference to any other frames. That is, they are compressed using just the information in the frame itself, in the same way still images are compressed (using the DCT, quantization, run-length encoding, etc.). This is called intracoding. There are generally two or more I frames each second (more often three to six), and particularly complex frames are encoded as I frames.

P and B frames are encoded with reference to the previous frame, i.e., they are intercoded. P frames are encoded with reference to a previous frame, called forward prediction.

B frames are encoded with reference to both the previous frame and the next frame. This is called forward and backward prediction.

Use of forward and backward prediction makes a high compression rate possible, because it is necessary to record only the changes from one frame to the next.

An I frame plus the following B and P frames before the next I frame together define a Group of Pictures (GOP). The size of the GOP can be set to 8, 12, or 16 to optimize encoding to suit different movies and display formats.

Macroblocks are blocks of 16 pixels by 16 pixels within a frame.

The encoder uses motion compensated prediction for P frames and B frames. That is, it detects macroblocks that don’t change from one frame to the next, or that change only by moving. For each macroblock, a search is made for the closest match in the search area of the previous picture. When a match is found, a motion vector is computed. The motion vector records how far the macroblock has moved, and in what direction.

[Chuck Engels]

And these are part of the reasons why MPEG is not a good editing format

[RJ Johnston]

If you open an MPEG-2 file in GSPOT, GSPOT will show you the number of I,B, and P frames and the distance between each.