Comments on: video editing with gopchop http://www.outflux.net/blog/archives/2005/04/28/video-editing-with-gopchop/ code is freedom -- patching my itch Tue, 06 Jan 2009 10:01:20 +0000 http://wordpress.org/?v=2.5.1 By: Ted Gould http://www.outflux.net/blog/archives/2005/04/28/video-editing-with-gopchop/#comment-21 Ted Gould Fri, 29 Apr 2005 18:17:46 +0000 http://outflux.net/blog/archives/2005/04/28/video-editing-with-gopchop/#comment-21 It, ofcourse, depends on your MPEG stream. There are MPEG streams that do not contain sequence or GOP headers, nor I frames. None of those are required in an MPEG 2 stream. The idea of a GOP is really more an MPEG 1 structure, that is supported in MPEG 2. But, for the most part, they aren't used as much in MPEG 2. It, ofcourse, depends on your MPEG stream. There are MPEG streams that do not contain sequence or GOP headers, nor I frames. None of those are required in an MPEG 2 stream.

The idea of a GOP is really more an MPEG 1 structure, that is supported in MPEG 2. But, for the most part, they aren’t used as much in MPEG 2.

]]> By: kees http://www.outflux.net/blog/archives/2005/04/28/video-editing-with-gopchop/#comment-20 kees Fri, 29 Apr 2005 00:52:48 +0000 http://outflux.net/blog/archives/2005/04/28/video-editing-with-gopchop/#comment-20 Yes, this is possible, also, and is just as "correct". With gop chop you may not be continuing on to the next GOP, so it's just as wasteful, unfortunately. There are also unusual streams that have LONG chains of B/P frames. :) Yes, this is possible, also, and is just as “correct”. With gop chop you may not be continuing on to the next GOP, so it’s just as wasteful, unfortunately. There are also unusual streams that have LONG chains of B/P frames. :)

]]> By: Ted Gould http://www.outflux.net/blog/archives/2005/04/28/video-editing-with-gopchop/#comment-19 Ted Gould Thu, 28 Apr 2005 20:41:05 +0000 http://outflux.net/blog/archives/2005/04/28/video-editing-with-gopchop/#comment-19 Well, you shouldn't have to put in an end of sequence or an end of GOP header at all. You should just have to send the next picture header. I'm not sure how libmpeg2 works, but MPEG, in general, only saves two pictures behind -- which are the last two anchor frames. But, one of those should be displayed, so only one hasn't been. Depending on your software encode, I'm guessing the first picture of your next GOP would be an anchor frame. So, when seeing that, the MPEG decoder should pop out the undisplayed anchor frame for presentation. Hope that works, e-mail if you have questions. Well, you shouldn’t have to put in an end of sequence or an end of GOP header at all. You should just have to send the next picture header. I’m not sure how libmpeg2 works, but MPEG, in general, only saves two pictures behind — which are the last two anchor frames. But, one of those should be displayed, so only one hasn’t been.

Depending on your software encode, I’m guessing the first picture of your next GOP would be an anchor frame. So, when seeing that, the MPEG decoder should pop out the undisplayed anchor frame for presentation.

Hope that works, e-mail if you have questions.

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