can you help me about "close gop"

[yani]

can you tell if that is correct

I encoded all my video dv with cinemacrat 2.64 and authoring with scenarist the setting of the encode was 3 pass VBR for the setting video I active dvd compilation but I have active close all gop in the gop menu

a friend off me say if this is not active you mpeg2 file can not be read in a standalone dvd player can you confirm that I'm very sad

can you tell me if he has a way to correct this on a mpeg2 file


thanks

[pijetro]

I'm not familiar with anything you're talking about, but I once read that closing Gop's is helpful if you plan on editing the .MPG's for future use.

Good luck!!!!!

[yani]

hello

I just want to know if a video mpeg2 compress without close gop can be compatible with sandalone dvd player

sorry for my english

yani

[pijetro]

Are you asking "can you get away without closing gop's for standalone playback?"

The answer would be yes, since Tmpgenc and CCE uncheck this default anyways, and it's what I run for standalone players.

I've never had to check the box for closed GOP's, but can guess that it should be okay. Like I said, I'm sure this helps for someone who plans on video editing the mpeg 2 file(because mpeg is tricky to edit, closed gop's help the encoding software). But it should work also for simple encoding for standalone.

Give it a try. Two short tracks, one with, one without closed GOP's.
Sorry I couldn't help you any more. I'm just pulling from what I've read on previous posts.

Good luck!!!!

[Zeppeliner]

I've only had to use it once, when I encoded two video files for use in a multi-angle dvd movie. The rest of the time I leave it unchecked.

[Boulder]

Read the CCE manual (downloadable from the CCE website). It contains a thing or two about the different options;)

[Arky]

Yeah, closed GOPs are mostly used for multi-angle titles, where you need to jump from one stream to another without unsightly jumps as you do so. Because the GOPs are closed on multi-angle MPEG streams, there is always a reference frame to jump to within extremely close proximity, which would would not be the case with open GOPs, where so many B and P frames reference of *distant* I frames. Closed GOPs can also help where you need to be more accurate with your chapter markers/placement, although one doesn't usually have to be overly accurate with these.

One DOWNside to using closed GOPs, and the reason many people choose not to use them, when authoring single-angle titles, is that because the I-B-P GOP structure is tighter, there is a reduction in efficiency of the MPEG compression process. The whole point of the MPEG compression process is that B and P frames use less bitrate than I frames. If you reduce the number of these "diluted" (but by virtue of being diluted, efficient) frames *relative* to the number of reference I-frames, then of course you will end up using more bitrate, or to put it another way, you'll create a bigger file for a given bitrate specification, because there are more I frames created, *relative* to the number of B and P frames. For the most part, this drop in efficiency is pretty negligible, but it's worth bearing in mind, if space is at a premium and you are trying to squeeze the last ounce of quality from long source footage onto a DVD-R, or even a CDR. Personally, when authoring single-angle titles, I used to sacrifice the drop in efficency and happily use closed GOP encoding on all my MPEG2 streams. These days, however, I find myself using open GOPs for much of my work, and have very little trouble with this approach unless I am working on a job which requires many, very closely adjacent, chapter markers in a given stream, in which case the closed-GOP approach suits me better.

The above is not a scientifically-precise explanation, so I daresay those of you with a textbook on your laps will be able to pick fault with it, but it should serve as a reasonable, brief, explanation of why one should consider using either open or closed GOPs depending on the circumstances of their project!


Arky ;o)