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31st August 2018, 16:22 | #21 | Link | |||
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One could actually think of --aq-mode 3 as "--sdr-opt." Quote:
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31st August 2018, 23:54 | #22 | Link | |
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At least if the guy knows what he's doing. I can imagine that plenty of self thought hobbyists and youtubers etc aren't aware of this and just 'play around' until it looks acceptable to them. But ask any big studio that knows what theiy're doing and they will confirm this. |
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1st September 2018, 01:28 | #23 | Link | |
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Although I hope we get one someday. ACES has demonstrated some good visually lossless compression with linear float, and I think a lot of block-based motion compensated techniques in the frequency domain could be applied to linear float. |
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29th October 2018, 08:01 | #24 | Link |
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In case someone else is working with HDR sources and does CRF encoding: you need to lower CRF quite a lot compared to SDR sources. I did some testing with an episode of Game of Thrones S01 and the result was that CRF 15 produced sufficient quality when the final resolution was 1080p. With SDR sources, CRF 20.5 is the sweet spot for me.
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29th October 2018, 18:36 | #25 | Link | |
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31st October 2018, 10:23 | #26 | Link | |
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Most HDR encodes will be about half the size and half the quality of the equivalent SDR encode at the same CRF. Last edited by RainyDog; 31st October 2018 at 14:03. |
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31st October 2018, 10:36 | #27 | Link | |
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Grainy sources level it out somewhat as grain and noise just attract bits regardless. But I just don't think the encoder is properly adapted to deal with non tone-mapped HDR sources really. |
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31st October 2018, 11:43 | #28 | Link |
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Yes, both were used, aq-strength 1.0. I actually ended up using CRF 14 for the first Harry Potter movie, average bitrate was around 7.5 Mbps 25% into the encode (very light denoising and downsizing to 1080p). I also feel that the bits are allocated based on the same flat image you see when you view the video on a non-HDR display, so it really cannot be optimal.
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31st October 2018, 14:18 | #29 | Link | |
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Bare HDR sources don't have the tone and luminance variation of SDR sources as that mapping is added by the decoder. So the encoder doesn't have that as a basis for bitrate distribution which would otherwise be a huge factor in where bits are allocated with SDR sources. |
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8th November 2018, 07:46 | #30 | Link |
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So the takeaway for HDR sources is currently:
lower your CRF about 3-5 for HDR encodes and avoid aq-mode 3 and 2 - is that correct? Does this also apply for encoding in UHD? (some ppl in this thread downsized to 1080p) |
8th November 2018, 10:08 | #31 | Link | |
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Depends what bitrates/quality level you're aiming for though, really. There's still a solid case for aq-mode 1 being the most dependable, balanced and safest mode for transparent high bitrate encodes though. Same should be applicable to 1080p or 2160p. |
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8th November 2018, 13:55 | #32 | Link |
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Well if u r downsizing UHD to HD such a low CRF might make sense.
But when u keep the original resolution CRF values below 16 often result in compression ratios not worth the encoding time or when the source is noisy even in larger than original sizes |
10th November 2018, 00:41 | #33 | Link |
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I found that bumping the AQ-Strength quite a lot can be helpful to retain the low contrast details better. (Since more AQ-Strength will focus the bits more on flatter/textured areas instead of edges/lines/higher contrast areas, thus it balances things out a bit better, though obviously not ideal)
Which confirms my initial thought that x265 doesn't take into account how HDR footage will be displayed and analyses it the same way as it analyses SDR footage. (so, low contrast areas will be seen by x265 as even flatter areas and thus will be blurred out or even result in banding). Currenly I'm encoding some HDR footage (it is 1080p though) with AQ-Strength bumped to 1.8, Qcomp to 0.7 and SubMe 7... Which brings it a bit 'closer' to expected results (still not as good as it could be imho). Last edited by K.i.N.G; 10th November 2018 at 01:52. Reason: added some more info |
10th November 2018, 01:50 | #35 | Link |
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Currently, with this encode, I'm using 2 but with no perticular reason. Normally I like 1 more... Bit I figured I'd try 2 for once because some ppl seem to recommend it, so I thought it might help with this. Maybe it's better for HDR... I'll do the same encode with mode 1 after this, so I can compare but thats going to take a few days so...
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10th November 2018, 02:12 | #36 | Link |
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Please keep us posted, it's interesting to know if there are any differences. I've made only one HDR encode so far but didn't do any comparisons but just used the default aq-mode and strength.
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12th November 2018, 19:14 | #37 | Link | |
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We'd generally expect 2 to be better than 1 for most (but not all) content. And we'd expect 3 to be better for SDR as SDR has sparser code values in low luma than high luma. We'd expect 2 to be better than 3 for PQ curve HDR because PQ is much more perceptually uniform and has plenty of low-luma code values. I'm not sure what would be best for HLG HDR. |
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12th November 2018, 19:16 | #38 | Link | |
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are you using --hdr-opt? I find it interesting that folks are talking about subme 7 as being useful. That's two steps beyond placebo! I'd love to see some A/B comparisons where folks have seen a difference with it. |
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12th November 2018, 19:21 | #39 | Link |
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What does the "auto variance" actually mean? I've always thought that aq-mode 1 is already some kind of automatically varying mode based on qg-size.
On HDR sources, mode 2 seems to produce noticably smaller files for the same CRF than mode 1. This would somehow point to the problem with the flat, non-tonemapped image x265 seems to use while analyzing things. Using aq-strength 1.8 for mode 1 makes the bitrate shoot through the roof compared to strength 1.0. I'm going to do some visual compares as soon as I have the time, but it's difficult because a 2-pass encode is a no-no since I'm not hitting a specific size. Comparing those two strengths at the bitrate that strength 1.0 produces at CRF 15 or so is not fair because strength 1.8 would require so much more bits.
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12th November 2018, 19:27 | #40 | Link | ||
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