Posted: Fri 17 Nov 2006, 1:20 Post subject: A GOP Question
I remember that in a book, it's said if a video file does not finish exactly at the end of a GOP, then dummy frames will be added to complete the GOP. It seems all the GOPs should be complete. Is it right?
If it's right, then here's the question. many editting softwares allow us to set key frame or DVD chapter markers manually, DVD chapter markers should be at the beginning of a GOP, right? then if those key frames or markers do not locate at the exact beginning of GOPs, what will happen next?
Joined: 04 Feb 2003 Posts: 587 Location: Lisboa, Portugal
Posted: Fri 17 Nov 2006, 7:11 Post subject:
I'm not sure what you mean by "all GOPs should be complete". All GOPs are complete in any file that isn't damaged. If you mean "are all GOPs identical in length?", then no, that depends on the encoder. Most encoders will simply make the last GOP shorter, if there aren't enough frames in the original.
As to the keyframes and chapter marks, it's up to the MPEG encoder to start a new GOP at the frames you define as "keyframes". In TMPGEnc you can do this by using the "force picture type" option.
If you select a different frame as a chapter start in your DVD authoring application, it will simply place the chapter mark at the nearest GOP start.
yes, I was just not sure whether all the GOPs should be the same structure/length as we has chosen in the GOP setting of a mpeg encoder.
if different length is allowed, then no puzzle any more. thanks.
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