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9th December 2009, 01:17 | #81 | Link | ||
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For example there are "sharp" matrices tuned to keep fine detail at high bitrates. Such a matrix will give horrible results at medium/low bitrates. At the same time there are "smooth" matrices tuned to keep reasonable quality at low bitartes. Such a matrix won't give satisfactory results at medium/high bitrates. In short: Don't use a custom matrix, unless you know exatcly what you are doing and why you need a non-standard matrix. (Note: H.264 is known to give best results with the standard "flat" matrix. Psy optimizations, as implemented in x264, usually work better than custom matrices) Quote:
size = bitrate * duration Well, given that the rate control of your encoder works properly and doesn't fail with non-standard matrices
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9th December 2009, 02:25 | #82 | Link |
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I need to experiment to understand the usage. Practical knowledge and examples help me understand better. Anyway, I am wanting to have a low and medium bitrate based matrix. I am trying to understand each matrix in the CQM editor.
The higher the bar means all details below that threshold will not be encoded - that means they will remain as it is? You think you could help me understand it during your free time? I would really appreciate it. I won't take long to understand as I have been reading and grasping stuff for quite a while now . P.S. I am mainly looking for XviD and HD (x264) based matrix. |
9th December 2009, 15:44 | #83 | Link | ||
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Furthermore it is important to understand that all this high/low frequency to fine/coarse detail mapping only applies to I-Frames. In P- and B-Frames the story is a bit different: http://forum.doom9.org/showpost.php?...9&postcount=17 As said before: Most likely you won't ever need any custom matrices for x264. It works best with the default (flat) matrix. That's because most things people tried to achieve with custom matrices in the past is done by x264's Psy-optimizations nowadays, only in a better way. So again: Don't mess with custom matrices, unless you know exactly why you need them... Quote:
http://forum.doom9.org/showthread.php?s=&threadid=83125
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9th December 2009, 21:03 | #84 | Link | |
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* Will MPEG produce a good output result for larger file size and x263 for smaller 1 CD, for user which don't know what they are doing with matrix? * Will matrix keep more detail than default MPEG and x263? Last edited by kool; 9th December 2009 at 21:09. |
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9th December 2009, 23:11 | #85 | Link | ||
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MPEG is standard that defines many things, such as MPEG-1, MPEG-2, MPEG-4 ASP (implementd by DivX/Xvid), MPEG-4 AVC (H.264) as well as various audio and container formats. This question makes even less sense. Maybe you refer to MPEG-4 ASP quantization matrices ??? MPEG-4 ASP (as implemented by Xvid and DivX) supports two types of quantization. They are called "MPEG" and "H.263". Only the "MPEG" quantization type allows custom matrices. Whether a custom matrix gives any benefit over the default matrix depend on what you are trying to achieve. But an unsuitable matrix can easily screw up your encode!
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9th December 2009, 23:16 | #86 | Link |
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Okay, so I will try to understand DCT first. I will try to get a *study* partner for this as a few imp. things go over my head.
One question, I like the H.264 matrix a lot and I was wondering if there is a way to use that matrix for XviD encodes? I have read mixed reviews on H.263 for 1CD and MPEG for 2CD encodes, and someone said H.263 is way better than MPEG. If that is true then why not use H.263 for 2CD+ encodes as well? How different is H.263 for H.264 and is there a method to incorporate the detail preserving matrices of H.264 in H.263? Last edited by n0an; 9th December 2009 at 23:18. |
9th December 2009, 23:21 | #87 | Link |
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Quantization in H.264/AVC is completely different from MPEG-4 ASP. Therefore H.264 quantization matrices are not even comparable to MPEG-4 ASP matrices!
And to make this clear again: For MPEG-4 ASP (Xvid/Divx) the "MPEG" and "H.263" quantization types are not different quantization matrices. They are two different types of quantization. Only the "MPEG" type can use custom matrices (as replacement for the default one). That's not possible with the "H.263" quantization type. However the "H.263" type is known to create a slightly "smoother" image than the "MPEG" type (with standard matrix). Generally "H.263" seems to be preferable for low bitrate encodes.
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10th December 2009, 00:47 | #89 | Link | |
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Could you tell me how to understand the structure of a matrix in the CQME? I want to use it as a visual aid to learn better . |
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10th December 2009, 11:40 | #90 | Link |
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Don't think that's possible. H.263 and MPEG are two different types of quantization. If you use a "custom" quantization matrix, then you definitely use the "MPEG" type, as the "H.263" type doesn't offer a way to use custom matrices. Also those quantization types cannot be "mixed", because you either use the one or the other...
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10th December 2009, 12:34 | #91 | Link | |
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I am currently encoding a 1hr 50min movie for 1CD at 780 kbps and a 2hr 50mn movie for 3CD at 1300 kbps. Would you recommend me using the default ones or Sharktooth's? |
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10th December 2009, 12:56 | #92 | Link |
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For the last time:The MPEG-4 ASP standard allows two types of quantization, "MPEG" and "H.263". The standard allows custom matrices for the "MPEG" type only. Heck, the "H.263" type doesn't even have an equivalent to a quantization matrix! It's simply a different way of quantization. Or in other words: You can not make the "MPEG" type work like the "H.263" type just by using a different matrix.
And a quote from earlier this thread: Yeah, the matrix is always included in the bitstream (in the case of MPEG quantization)... H263 quantization is not actually a matrix, nor can it be directly compared or converted to one. It's just a method of quantizing that doesn't use weights (which MPEG does, and those are the quant matrix elements). That's impossible to answer for each an every source. Even the other Xvid settings you use may have an effect. But if you use an average bitrate higher than 1600 kbits, it may be worth a try. After all you must decide what looks better for your eyes. So either pick the easy way and go with the default matrix or do some testing!
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