Tell me something:
Why is it that in almost all video streams I see there are wierd gray bits in the black? Why does it seem like all the encoders do light scenes 300% better than dark? Why can't encoders make black simply look black?
Also, is there any way I can fix this? Is it post-processing problems?
Thanks!
crappy gray bits
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Ashton
- Joined: Mon Jul 23, 2001 11:52 am
- Location: Northern California
- Contact:
crappy gray bits
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オタク同士やろう！ Ashton
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AbsoluteDestiny
- Joined: Wed Aug 15, 2001 1:56 pm
- Location: Oxford, UK
- Contact:
It's a problem with quantization.
When video is compressed, there is a quantizer matrix. This is a bunch of numbers known by the decoder that simplify the data to make it easier to compress.
Quantization has an inherent "rounding" effect. This rounding effect is most noticable in certain areas:
smooth gradients become banded
areas of black get rounded up to grey
They actually exist throughout a lot of the image but you don't always notice them. The reason you don't notice them much in the light areas is because your eyes are less sensitive to changes in very bright things (which is what lumi masking is all about).
There have been attempts at reducing this problem - a thread at doom9 suggested a mixture of a lumgain and unfilter. However, it is an inherent problem with these kinds of codecs and at lower bitrates can also be observed in mpeg2.
When video is compressed, there is a quantizer matrix. This is a bunch of numbers known by the decoder that simplify the data to make it easier to compress.
Quantization has an inherent "rounding" effect. This rounding effect is most noticable in certain areas:
smooth gradients become banded
areas of black get rounded up to grey
They actually exist throughout a lot of the image but you don't always notice them. The reason you don't notice them much in the light areas is because your eyes are less sensitive to changes in very bright things (which is what lumi masking is all about).
There have been attempts at reducing this problem - a thread at doom9 suggested a mixture of a lumgain and unfilter. However, it is an inherent problem with these kinds of codecs and at lower bitrates can also be observed in mpeg2.
