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I think most of our questions regarding the GOP could be answered with a sophisticated MPEG analyzer. Anyone know of such a beast? |
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But my question remains: Why P=max GOP? and why 15 (just on example)? If I count correctly, the GOP is cutted between a 2nd and a 3th B frame (not the best place to stop) |
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Jim |
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U can use any number , ANY number ! (like 5823 - signature of KWAG) :D It can be big any size but not less than optimal value - THE ONE our Bright minds are serching for 8) :? Size of GOP depends on MAX frame numbers in gop . This number is responsible on GOP size . bman |
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A low CQ_VBR doesn't make more of this kind of noise. It might make "mosquito noise", but it's not really noise at all. We should probably start calling it the Gibbs Effect instead :). |
8O wow, kwag and others... now this is getting really odd...
So as I understand ya'll correctly :) ... There's an optimal GOP for each resolution + for each CQ_VBR value of this resolution ? Let's just go ahead and test... I'll run a couple of tests on the PAL templates, of the KVCDx3... later guys... |
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so what I really meant was that this thing we are contemplating could really turn out to be a tough case. In my tests GOP size 36 frames produced a slightly smaller file than a 30-frame GOP. Then again, I got the smallest filesize with a max 8-frame GOP..confusing! I just hope that this value would only depend mostly on the resolution. |
I think I know what we have to do. If for a given CQ_VBR there is an optimal number of max frames, we need to calculate a formula that applies either a negative or positive offset to a pre-determined center point of max frames. This way, when we change the CQ_VBR value, the max frames is adjusted. Of course with a minimum value and maximum values. Like MIN_P=6, MAX_P=36.
-kwag |
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I think it's time for SansGrip to start planning another util..THE P-REDICTOR!
Jesus, we'll need more time predicting the GOP size and the CQ_VBR value than encoding the movies :lol: |
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(And by "P's" you mean "pictures", not "P-frames", right? :?) |
Opps, sorry SansGrip, I had edited the post, but you beat me to it on the quote :D I meant max number of frames. Not P's.
-kwag |
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ARGH!! WE'RE ALL POSTING AT THE SAME TIME!!!! :lol: :mrgreen:
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We go on like this, this thread will have 20 pages by the end of the day :lol:
At this speed, we'll probably have a solution to all of this in a matter of hours :mrgreen: -kwag |
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To be honest, if this thing gets included in the KVCD Predictor, it's going to be the sliced bread of amateur(?) video encoding, if you see what I mean 8) |
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It involves selecting several sample strips (say, "this represents the average amount of action in the film", "this represents more sedate scenes", "this represents particularly high-action scenes", or whatever) and encoding them, then running them through an MPEG analyzer to determine how efficiently each strip is using the CQ_VBR and GOP settings, then generate a new template (incorporating "force picture type" settings) to use based on the analysis, then repeat... Sort of like a feedback loop, all in one program... 8O |
Another thought...
wrt the analysis idea, if one were to go through the encoded sample strip and calculate the average size of I-frames, P-frames and B-frames, shouldn't it be possible to calculate the best GOP structure from that information?
In other words, let's say we had the following results from the analysis (numbers are made up and probably bear no resemblance to real figures): Avg. I-frame = 25kb Avg. P-frame = 10kb Avg. B-frame = 5kb This information would suggest a large GOP, with as many P- and B- frames as possible. The question is, what would the average sizes be for a movie that compresses better with a smaller GOP? Could it possibly look like this: Avg. I-frame = 20kb Avg. P-frame = 22kb Avg. B-frame = 25kb :?: What else would account for the phenomenon? |
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