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Old 5th June 2020, 18:57   #21  |  Link
MGarret
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Yes, that's exactly what it is. Some broadcast hw encoders had that feature for years. They have "default" interval that is further "extended" in case of a detected scenecut.
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Old 5th June 2020, 21:39   #22  |  Link
benwaggoner
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Originally Posted by MGarret View Post
Yes, that's exactly what it is. Some broadcast hw encoders had that feature for years. They have "default" interval that is further "extended" in case of a detected scenecut.
So, same worst case, but shorter average GOP duration. Makes sense for channel-switching optimization. Less so for most other scenarios.
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Old 7th June 2020, 23:09   #23  |  Link
kolak
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So, --keint 50 --gop-lookahead 25 would still have a max GOP duration of 50 frames, but the average would tend to be closer to 50 than 75?

Seems worthy of some testing.
Max would be 75.
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Old 7th June 2020, 23:10   #24  |  Link
kolak
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Originally Posted by Blue_MiSfit View Post
My interpretation is that the nominal GOP length would be 50, but that it might be as high as 75 in some cases, if a scenecut is found within that extra 25 frames.

Put another way, starting at frame 0, assuming scene change detection is not triggered from frames 0-49, frame 50 will be an IDR... UNLESS frames 51-74 are flagged by scene change detection, in which case the earliest of those will be the IDR.

At least.. I think I did the math right there I always have to think twice about duration vs frame number etc!
This is how it seems to work.
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