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6th June 2008, 02:50 | #82 | Link |
x264 developer
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Yes, in my experience so far it is incredibly good at keeping the dither that gradbun2db introduces as long as you give it enough bitrate (while without, regular x264 will generally butcher banding even at absurdly high bitrates).
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6th June 2008, 03:13 | #83 | Link |
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I've tried it on quite a bit of animated material now, and have got to say I'm very impressed.
Would I be right in assuming that although psy rdo is activated by default at >subme 6, it's optimised to process an image based on how grainy/noisy it is, including fine texture/detail, etc (in other words good on clean, grainy, or mixed footage)... whereas fgo by nature assumes a source is grainy/noisy, and could therefore be detrimental to a source that has both clean and grainy scenes? |
6th June 2008, 03:18 | #84 | Link | |
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6th June 2008, 03:25 | #86 | Link | |
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One thing I may see is if I can combine the two; Psy RD uses a 4x4 and 8x8 transform for comparison, while FGO uses a 2x2. Maybe I could combine all three transforms? |
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6th June 2008, 04:13 | #88 | Link |
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With these visual improvements (VAQ and Psy RDO), I wonder if CQMs still have a large impact on image quality. I always have Sharktooth's AVC CQM on, even with animated material, but I haven't tried without it yet. Encoding a full length animated episode is incredibly slow on my lappy. You think CQMs will still remain significant at this stage (given a reasonably high bitrate/resolution)?
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6th June 2008, 04:20 | #89 | Link | |
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If you want to make comparisons, short samples should probably be sufficient. |
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7th June 2008, 01:27 | #91 | Link |
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1) When you're actually trying to keep fine detail, they butcher it.
2) They skew x264's lambda values. 3) They confuse RDO. 4) They confuse trellis even more than they confuse RDO. 5) Prestige, especially, does some really bizarre things. |
7th June 2008, 01:53 | #93 | Link | |
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First, on the topic of RDO, you can intentionally make CQMs so that RD-wise, the inter matrix will always be favorable (for example), and so inter blocks are nearly always used when in RD mode. However, the creator of the CQM might not have intended this; for example, the CQM might have been intended for an encoder that didn't use RDO, and therefore would not have taken into account the CQM when making its decision. I strongly suspect Prestige is this sort of CQM. With trellis, trellis simply does not take into account CQM weights when working. I've found doing so actually reduces visual quality, unless I made a mistake in my patch--go figure. |
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8th June 2008, 01:01 | #94 | Link | ||
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x264_x86_r871_techouse Quote:
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8th June 2008, 06:55 | #95 | Link |
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12th June 2008, 21:18 | #96 | Link | |||
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12th June 2008, 21:22 | #97 | Link | |
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Also I think features like VAQ, FGO and Psy RDO do exactly what people tried to achieve with CQM's before, only in a more sophisticated and more general way. IMO it's always better to resolve the cause of the problem itself instead of fighting the symptom of the problem...
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13th June 2008, 01:59 | #98 | Link |
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An ideal AVC encoder would vary the quant matrix per frame to completely maximize RD. That's one of those exponentially hard problems though, unless someone comes up with a good way to quickly test whether a CQM benefit outweighs its size every frame.
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13th June 2008, 02:32 | #99 | Link |
Derek Prestegard IRL
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I had an idea for something similar back in the Xvid days, but it would have been very time consuming, and required a lot of user interaction. Here's how I saw it:
1) Take a movie, and split it into comp-test style chunks 2) Encode this multiple times with different CQMs 3) Show the compressionist the individual chunks, with the ability to flip between versions easily, stackhorizontal, interleave, whatever. 4) Allow the compressionist to pick a "top 3" or something for each chunk 5) Tally the votes, and pick a CQM for the movie. I wish I could code, or I would have cobbled this together just out of curiosity. But back on topic - I'm a huge fan of PsyRDO. It's improved almost every single thing I've thrown at it. ~MiSfit
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