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14th April 2024, 23:23 | #2241 | Link |
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If you have to know and specify the parameters for ffmpeg always that way...
Guarantee for generating wrong frames. Moreover - it can't be just the command line, as ADM for example exports/ shows the same frames as "default command line". But maybe ffmpeg API has to be called by the hosts also in the specific way respectively? ... and isn't... |
14th April 2024, 23:37 | #2242 | Link | ||
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ffmpeg is constantly evolving project - sometimes stuff gets broken, then fixed or behaviour changed There are many "gotchas" and pitfalls with ffmpeg - it's not for beginners The PNG gAMA and cHRM that ffmpeg exports is another common problem Quote:
avidemux never has the correct color for me in any of the versions going back 10 years. I couldn't figure the correct combinations twiddling in the settings / open GL / QT/ DXVA . If anyone is able to get avidemux to have correct colors, please post the setup configuration |
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15th April 2024, 00:51 | #2243 | Link | |||||||||
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https://en.wikipedia.org/wiki/Floati...ror_mitigation Quote:
now do that in your round trip. someone didn't think before. because i literally wanted you to embarrass give me that answer... Quote:
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and not the point. why would you not dither them that's the point. Quote:
just like something is lossy. Quote:
It has nothing to do about "wanting" . It has to do with using real video values, with real encoding[/QUOTE] my point is they are inaccurate. you know you can encode a dithered image. well i can... Quote:
well i give you 8 because most of these renderer can't render at more. i guess you simply didn't know that. not that your round trip ever matter. for some reasons you really care for illegal colors... a renderer obviously can't show. and that's why it is basic knowledge that YCbCr -> RGB is lossy in the video renderer realm. why do i have to say this out loud... Quote:
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and the best part sampte say it should be 191 0 0. what a grand and intoxicating innocents. it's just like YCbCr -> RGB is lossy when it is actually used to look at it in you know a video renderer. BTW. because for some reasons you really don't get it. MPC-HC can not change any color inaccurate in renderer they are all up stream it just loads them. EVR everything is in the hand of the GPU driver and the rest is 3rd party. this is like complaining to a post worker that the weather is bad. Last edited by huhn; 15th April 2024 at 00:55. |
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15th April 2024, 01:37 | #2244 | Link | ||||||||||||||
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To do the round trip properly you must use RGB float for the intermediate step e.g. a vapoursynth script. A regular player setup will clip values for the YCbCr => RGB intermediate step Quote:
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=> This part of discussion with the round trip all started with your statement: Quote:
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I wrote integer YCbCr => float RGB => integer YCbCr is lossless when done properly. Do you see the difference ? Quote:
The point about disabling dithering for diagnosis/analysis is about comparing to different programs, some using different dithering algorithms or not. You need to compare "apples to apples". If you have some random seed producing different results, it's going to mess up the analysis . You need to perform multiple tests to determine the underlying problem. Not just 1 test with dithering. There can be many reasons for an observation. eg. It looks to me here this was user error for nji Quote:
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15th April 2024, 02:56 | #2245 | Link | ||
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Ahh I glossed over this and missed it - 192,0,1 , not 191,0,0 - ie. you're referring to the 8bit case. I see what you're getting at... Same methodology comparing to float signal 8bit "75% red" YCbCr[51,109,212] PSNR 32bit (0-100 scale) no dither r 50.629359 g 100 b 48.130803 ordered dither r 54.435493 g 71.785649 b 52.805518 Quote:
Last edited by poisondeathray; 15th April 2024 at 03:08. |
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15th April 2024, 11:42 | #2246 | Link |
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If I get it right, the question about dithering etc. is independent
from the one I originally raised (potentially brightening by MPC). As my effects are much larger than the ones discussed above.. A short sum-up. @poisondeathray confirms my observation at his configuration. ==> Either MPC or ffmpeg is wrong. What does it mean that ffmpeg produces this overall different and especilly green-brighter frames with unflagged videos? Is this another bug of ffmpeg? https://forum.doom9.org/showthread.p...26#post2000426 To my opinion it is important to come to a conclusion to have consequences. If not, everything is blown in the wind. For me it seems unacceptable ffmpeg has to be fed carefully by stream information externally to produce a correct output. Identifying the streams in detail and correctly should be its origin ability. The central question: Is ffmpeg doing wrong? If yes - there should be filed an issue. |
15th April 2024, 12:05 | #2247 | Link |
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without metadata you have to guess.
and a guess will never ever be 100 % correct. it is still a guess. so it can do "better" guessing by seeing ohh 720p that not a DVD that's a bd resolution so bt 601 or the many other dvd colorpspace thingies are unlikely let's take bt 709. not worth to do to break older scripts that rely on the old guessing. it can still be bt 601 anyway or what ever ycocg anyone? the solution is tell it what it is. |
15th April 2024, 12:52 | #2248 | Link | |
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The explanation is wrong matrix is used . It's similar to the behaviour I mentioned earlier with vdub2 with Rec601 . If no flags (or unknown), then assume Rec601. But.... by convention, HD video uses Rec709 , SD video uses Rec601. So you can see that will be a problem in actual usage for unflagged videos... and there are many unflagged in the wild . Some video players use an additional level of logic - if height > 576 then use Rec709 for the RGB conversion It's not considered a bug, and this one has been reported dozens of times The other problem is wrongly flagged videos - it happens a lot more than you think. Another can of worms Last edited by poisondeathray; 15th April 2024 at 12:55. |
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15th April 2024, 13:41 | #2249 | Link |
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Your explanation seems very plausible to me.
If it should be right (with my very limited knowledge and experience I can't assess, but as we're in a forum maybe there will be other posts on this). ... so IF that should be right.. ... then it's a built-in source of wrong color changes. It's not me having a solution for it. Still I wonder if a wrong/ missing flagging actually explains the (2,2,2) at my movie? It is a 720p flagged BT.709, limited range. The orig movie is from 1989. Last edited by nji; 15th April 2024 at 13:52. |
15th April 2024, 15:36 | #2250 | Link | |||
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Were you referring to color-test.mp4 ? Using default settings ? Your video is flagged, you can see in mediainfo for example Color range : Limited Color primaries : BT.709 Transfer characteristics : BT.709 Matrix coefficients : BT.709 The default ffmpeg scaler responsible for the YUV=>RGB conversion is swscale. The important flags for swscale higher accuracy are Code:
-sws_flags accurate_rnd+full_chroma_int Why isn't this the "default" setting ? I don't know . I'm guessing probably a speed / performance tradeoff I think most regular ffmpeg users prefer zscale these days. It's faster, more accurate, fewer problems with cases . Why is swscale still the default ? Not sure, legacy, nostalgia - It's the one that everyone complains about and historically had many errors and problems |
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15th April 2024, 16:39 | #2251 | Link |
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I checked and... 100% approvement!
With the flags of swscale you mentioned the (2,2,2) difference is gone. I can't tell if "most regular ffmpeg user prefer zscale" as you said. I would have thought that most typical (occational) ffmpeg users like me never even heard about that, and use the default config. Trusting that ffmpeg does the right thing. The way it is now unwanted changing spread more and more. To my opinion worth an issue in ffmpeg. But you said it isn't taken as bug. Call me naive, but I'm kind of disgusted by that situation. And grateful to you |
15th April 2024, 23:10 | #2252 | Link |
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Good thread, many thanks for getting into that detail, poisondeathray, and the others.
I might have stumbled into that one (ffmpeg) too one day.
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Yesterday, 14:18 | #2255 | Link | |
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Can this anime pedo be banned please? No participation at all, except for being annoying.
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Yesterday, 23:35 | #2258 | Link |
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Just calm down.
Obviously it's useless with him - be free to leave that poor bugger with that. ("Don't feed the trolls.") Let's enjoy there a some really nice people here too. Last edited by nji; Today at 00:25. |
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