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12th March 2016, 17:39 | #2 | Link |
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... I tried to find anything related to this in the documentation, and it doesn't specify if zones work in nPass or only in CRF.
Is there a place where we can get that type of information? If indeed zones is not available for nPass encoding, it would be nice to update the documentation to reflect that... |
12th March 2016, 20:13 | #3 | Link | |
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If it doesn't work for 2 pass, you should file an issue on our Bitbucket issues tracker, complete with your test data. |
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14th March 2016, 00:43 | #4 | Link | ||
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Will update this thread after I get another encode generating a CSV. I also noticed that user LigH posted the following in the main x265 thread. Quote:
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14th March 2016, 09:39 | #5 | Link |
German doom9/Gleitz SuMo
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I already sent my results to the x265 Developers' mailing list. Just to present them here again:
The Sintel trailer in a smaller version (640×272, to fit inside 360p) was encoded in 3 passes each, once without zones, once with 3 zones as follows, using x265 v1.9+88: Code:
--preset slower --bitrate 1000 --zones 0,223,b=0.3/1140,1253,q=40 --pass [1|3|2] Just like the command line, "pass 3" (purple) means the middle pass and "pass 2" (red) means the final pass. As you would expect, the refined result of pass 2 is usually in between the ABR preparation (pass 1, blue) and the CRF result of pass 3. Now the quantizer distribution with 3 zones: 30% bitrate in the beginning (frames 0..223), constant quantizer 40 in the end (frames 1140..1253), and 100% bitrate in the middle (no explicit definition). The result of pass 3 is already not as expected, the bitrate gets lowered after the leading zone instead of during. At least the CQP zone is more or less respected. But pass 2 goes completely crazy, doesn't respect the trailing zone quantizer at all (10..12 instead of 40). The HEVC outputs and the detailed CSV logs are available in this archive. Last edited by LigH; 14th March 2016 at 09:42. |
14th March 2016, 10:04 | #6 | Link | |
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I'm afraid not. This is a little troublesome for the 'zone' that you first have to create the video to determine misalignment ranges the quantizer. Last edited by Jamaika; 14th March 2016 at 11:12. |
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14th March 2016, 11:34 | #9 | Link |
German doom9/Gleitz SuMo
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Jamaika, what are you talking about, at all?
The topic of this thread is that if one declares a zone where the bitrate distribution shall differ from the rest of the move, the bitrate shall change as desired, not randomly or even to the opposite. Nobody talked about the speed yet, and I doubt that the encoding speed of zones is generally lower than without (except for zones with smaller quantizers, producing bigger results). At the moment, all we discuss is: If I want x265 to make a scene smaller than normal, then x265 has to make it smaller than normal, not surprisingly bigger instead. |
14th March 2016, 23:59 | #10 | Link |
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LigH, there's already an issue logged for this issue on bitbucket: Issue #172 Bitrate control: Zones are ignored in any but the first pass in n-pass encodes
I will add my test results there, maybe you could do the same and promote the ticket so it gets resolved faster :P |
17th March 2016, 17:09 | #13 | Link |
German doom9/Gleitz SuMo
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Zones have been fixed in x265 1.9+96-b09998b1256e: Quantizer raises in pass 3 and 2 during the first zone (as expected for a bitrate target of 30%), and gets more or less close to the target of 40 in the last zone.
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28th May 2016, 13:11 | #15 | Link |
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Is possible to specify CRF rates to zones in x265 please?
For example the following works in x264 but not x265. --zones 0,32742,crf=28 --zones 90324,95154,crf=28 --zones 181728,186768,crf=28 I'm encoding a film which has a few scenes of heavy machine-noise like grain that I want to reduce the bitrate distribution to. The majority of the film is very clean though so I want a much lower CRF for the overall value. Thanks. |
28th May 2016, 21:41 | #16 | Link |
German doom9/Gleitz SuMo
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At the moment, it seems that only a bitrate percentage or a fixed quantizer are supported. But adding support for CRF zones would probably be interesting too. And I hope it won't be too complicated, not much harder than QP zones...
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29th May 2016, 07:56 | #17 | Link |
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Thanks LigH. Hopefully we see support for CRF zones in the not too distant future then.
In the meantime, what I've decided to do is add --vbv-bufsize 10000 --vbv-maxrate 10000 to the encode. I've run a quick x264 test encode without any bitrate limitations or zones and, looking at the bitrate graph, there's barely any spikes above 10-12mbps other than the flashback scenes with the heavy artificial grain/noise added (which shoot up to 50mbps+ if uncontrolled!). So the majority of the encode should be unaffected by the max bitrate limitation but the aforementioned grainy scenes will get capped at 10mbps. |
29th May 2016, 10:16 | #18 | Link |
German doom9/Gleitz SuMo
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If the encoder implements VBV checks correctly, then you can trust the result being decodable in a device with given limits.
From my experience in a DVD authoring studio, peaks are not your worst concern. I remember DVD Video material with occasional 13 Mbps GOP peaks causing no issues, but a permanent 10 Mbps burst being rejected by the authoring tool. The development of the bitrate during several seconds is the criterion, not a single GOP peak. |
31st May 2016, 19:32 | #19 | Link | |
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Quote:
For DVD, and all VBV cases, remember that a "peak" is measured over a number of bytes, so even if a single GOP is at more than 13 Mbps, the peak as defined by VBV can still be <10 Mbps. DVD GOPs are around half a second. average bitrate per GOP and peak bitrate converge a lot more with longer GOPs, but you can still have things that look non-compliant but aren't. And sometimes something that looks compliant that isn't, like if two clips are concatenated with the first ending in a peak and the second starting with a peak. Both could have been compliant by themselves, but VBV gets violated at the stich point. |
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31st May 2016, 21:23 | #20 | Link |
German doom9/Gleitz SuMo
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One reason of sudden bitrate bursts are also subtitles, especially when there are subtitle pictures in several streams at the same time. Hardly an issue in home made media, but certainly an issue in commercial DVD productions with more than half a dozen subtitle streams.
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