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h264-resource-wip:avchd [2012/02/20 17:17] driftwood [Quantization Scaling Tables] |
h264-resource-wip:avchd [2012/03/05 21:41] (current) driftwood |
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| - | Note from Driftwood (14th Feb 2012): This is a work in progress of AVCHD resource and info. Things we know need to be rewritten and simplified and put in here. Below is not the final order of the jigsaw - some of the sections may end up in other headings. I'm going to finish everything first, and then you guys can edit it down more. Everything is written in' my way of interpretation' ie nothing is copied from other sources - if its incorrect, correct it! | + | Note from Driftwood (March 2012): Being edited in Word & 'pdf professional' before being made into wiki.This is a work in progress of AVCHD resource and info. Things we know need to be rewritten and simplified and put in here. Below is not the final order of the jigsaw - some of the sections may end up in other headings. I'm going to finish everything first, and then you guys can edit it down more. Everything is written in' my way of interpretation' ie nothing is copied from other sources - if its incorrect, correct it! |
| ====== What is AVCHD? ====== | ====== What is AVCHD? ====== | ||
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| Using the same QM for both Inter and Intra frames is less efficient than using different QM's, because of the difference in method used. | Using the same QM for both Inter and Intra frames is less efficient than using different QM's, because of the difference in method used. | ||
| - | Finally, the standard Panasonic Lumix GXX matrices are already quite well made. The only reason I could see anyone using a custom QM is for increasing the amount of detail/size of a video (since for higher compression you could just as well use a higher quant, no need for a custom matrix) or for making things look softer and less sharpe. | + | Finally, the standard Panasonic Lumix GXX matrices are already quite well made. The only reason I could see anyone using a custom QM is for increasing the amount of detail/size of a video (since for higher compression you could just as well use a higher quant, no need for a custom matrix) or for making things look flatter or softer and less sharpe. |
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| + | <b>What is colour space - YUV or YCbCr?</b> | ||
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| + | In simplistic terms, component video's color space is also known as YUV or YCbCr, where Y encodes luminance, U or Cb (blue) the difference between the blue primary and luminance, and V or Cr (red) the difference between the red primary and luminance. The low chromatic acuity (clearness of vision) allows a percentage data reduction of the color difference signals. In digital video, this is achieved by chroma subsampling. | ||
| + | In AVC colour space profiles the notation used is as follows: | ||
| + | 4:4:4 = no chroma subsampling. | ||
| + | 4:2:2 = chroma subsampling by a factor of 2 horizontally; this sampling format is used in the standard for studio-quality component digital video as defined by ITU-R Rec. BT.601-5 (1995), for example. | ||
| + | 4:2:0 = chroma subsampling by a factor of 2 both horizontally and vertically; it is probably the closest approximation of human visual color | ||
| + | acuity achievable by chroma subsampling alone. This sampling format is the most common in JPEG or MPEG and in the GH2's AVCHD implemntation. | ||
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| DC transforms | DC transforms | ||