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8th September 2022, 20:24 | #1 | Link |
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Some questions about psy-rd
Hi,
I often tend to prefer lower psy-rd values, but first I'd like to know more about the following points : - Does it mostly depends on personal preferences since it's psychovisual, or is there any broader recommandations (excluding anime values recommandations and not going beyond 1.0) ? - Does lowering psy-rd have some advantages as well ? It seems at least better on flat areas and constrats from what I read here and there and from some tests I did. - I noticed that some psy-rd values appears to be less "stable", particularly between 0.6 and 0.9 : it causes some kinds of artificats that are more noticeable and bothering than those of 1.0 or 0.4. Could it be for a reason ? Thanks. |
16th September 2022, 18:01 | #2 | Link |
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There's more concrete to it than just personal preferences, but it certainly is somewhat content dependent. Generally higher values can be used with very low noise natural image content. And it interacts with a variety of other parameters, so even with the same content, the optimal value can vary some.
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17th September 2022, 18:48 | #3 | Link | |
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Quote:
I was barely focused on psy-rd but even though I have little knowledge about it, I realized it's not easy to determine a "nearly optimal" value. Currently, I find that values such as 0.8 or 0.7 are more or less better on most of my encodings, but the visual issues that come with those values made me wonder... (otherwise I'd just have slightly lowered the value to stay in a "safe range" and that's it. Whereas in this case, I have to lower it to something like 0.5 to have a sufficient visual balance on most of sources I tested) It seems even more weird when lower values are supposed to mean less visual issues, but it doesn't look that simple. Actually, what I was wondering is if it's generally considered "safe" to lower psy-RD at all ? (whatever the values are, excluding the impact on details and sharpness of course), and I'm also wondering if it's related to AQ (I may be completely wrong, but as far as I understand, Psy-RD works the opposite way of AQ, so I'm guessing their default values were intended to balance each other, which would then be something to consider). Anyway, I hope i'm not digressing too much and that it's less tricky than I think... Last edited by andiandi; 17th September 2022 at 18:52. |
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17th September 2022, 21:45 | #4 | Link |
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If you want to preserve as much as the original (inc. noise/grain), high values of both psy-rd and psy-rdoq can really help. Personally I use --psy-rd 4 and --psy-rdoq 15, the latter really helps eliminating banding.
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18th September 2022, 00:12 | #5 | Link | |
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Quote:
It's a tool to best test using a 2-pass ABR encode, so you can compare the impact on the settings at the same file size. Testing with CRF you get both quality and bitrate changes, so it's hard to tell if you're getting better psychovisual compression efficiency. |
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18th September 2022, 19:02 | #6 | Link | ||
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Quote:
I'm not using x265 for now (I would have liked to use it for archive purposes with high bitrates, but apparently x264 is better for this - the question about Psy-RD is for my regular encodings) Quote:
Last edited by andiandi; 18th September 2022 at 19:08. |
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