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8th July 2010, 23:50 | #341 | Link | |
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Quote:
Then open-gop wouldn't really be open gop, would it? But ok, the term might just be a "tradition" coming from older standards. |
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9th July 2010, 14:17 | #342 | Link |
Guest
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There are cases other than IDR where you do not have to go back a GOP. E.g.:
Recovery point SEI non-IDR I picture ... The sample posted earlier in the thread places recovery points before the non-IDR I pictures as above. In fact, in the very first post Trahald states that is what the "open GOP" patch does. I do not consider those to be open GOPs! For me a GOP is open if you have to go back a GOP to decode without errors. The decision whether to go back is quite tricky. I see it like this (coding order): IDR starts closed GOP. RPS+I starts closed GOP. I P B starts closed GOP. (This is the controversial one. Theoretically not so, but practically yes.) I B P starts open GOP. For me a GOP is just a sequence of pictures starting with IDR/I and it is seekable without going back if it is closed. Last edited by Guest; 9th July 2010 at 14:48. |
9th July 2010, 15:14 | #343 | Link | |
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This hole debate is a real mess when we do not have a common opinion on the definition of a gop (and/or forget to mention whether we're talking coded or display order). Is there any definition in the h.264 standard? |
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9th July 2010, 17:52 | #345 | Link |
Wewkiee
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blurays definition of open-gop says this
1. the first frame in decode order must be a non-idr i frame and the frames that proceed it in display order are allowed to reference forward and backward. these frames cannot be correctly decoded during a random seek and are skipped. 2. frames after the non idr i-frame in display order must NOT reference frames prior to the i-frame in display order. recovery points are not mentioned. (and there is plenty of room for a 'shall not' if that were the intent) the frames in 1. are always b frames in x264. p frames that preceed the i-frame in display order (yet follow in coded order) are allowed but x264 doesnt generate p-frames in this condition. if b-frame decision decides that b-frames arent needed following the iframe in display order, that gop will essentially be closed (again based on blurays definition). The command open gop is ignored when --bframes == none. blurays definition of open gop is the only one i know of. I modeled its behavior after AVC blurays.
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...yeah...but...why on earth would I compare apples with apples? Last edited by Trahald; 9th July 2010 at 18:00. |
3rd August 2010, 09:29 | #346 | Link | |
GPAC maintainer
Join Date: Jul 2010
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The compliant solution is implemented in GPAC. However it is not usable as seeking big files takes a lot of time. x264 (with GPAC MP4 support) marks all key frames as sync points, which is less compliant but practically allows you to seek within the file flawlessly. Practically, I would advise you to create your MP4 files using x264, and then adding your audio with: Code:
mp4box -add my_audio.xxx my_h264_muxed_with_x264.mp4 Romain |
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3rd August 2010, 18:59 | #349 | Link |
Spinner of yarns
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According to 14496-15, sync samples are just IDR-pictures, so treating a I-picture as a sync sample is out-of-spec.
(Current x264's mp4 muxer module sets key-frame (IDR or I) as sync sample.) I think it is the better solution using sdtp box (Independent and Disposable Samples Box) for marking random access point when Open-GOP is available.
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3rd August 2010, 19:40 | #350 | Link | |
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1st use x264s internal muxer to pack the videostream into a .mp4 file 2nd use mp4box to add additional streams ---- *snip* Cu Selur Last edited by Trahald; 4th August 2010 at 00:32. |
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15th August 2010, 12:53 | #351 | Link | |
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Quote:
Code:
>mp4box -add The Best of Science Fiction Movies_audio.mp4 The Best of Science Fiction Movies_video.mp4 Code:
Error - 2 input names specified, please check usage EDIT: SOLVED DOH, it needed quotes around filenames... Last edited by jethro; 15th August 2010 at 13:00. |
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