Re: YUV format

Ed Okerson wrote:
> On Fri, 27 Dec 2002, Holger Waechtler wrote:
> 
> 
>>Holger Waechtler wrote:
>>
>>>Dustin Stuart wrote:
>>>
>>>
>>>>YUV12 saves the chrominance planes at 1/4 the resolution of the luminance
>>>>plane right? because the eye is less sensitive to colour than shade.
>>>>
>>>>Instead of reducing the colour resolution, why not simply quantize the
>>>>colour information more heavily. This way the encoder could be more
>>>>flexible
>>>>about how much colour information is kept (hopefully reducing blocky
>>>>artifacts in areas where the colour changes abruptly).
>>>
>>>
>>>This is done anyway. Right now the U and V component images get 1/8 and
>>>the V component images gets 1/8 of the bit budget.
>>
>>   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>>sorry, this should read:
>>
>>...the Y component image gets 6/8, the U and V component images get 1/8
>>each...
> 
> 
> For the input mode of ppm files this is fine because you start out with
> the same size plane for Y, U and V (after conversion from RGB), but for
> YUV420 where the U and V planes are already 1/4 size, is it still
> appropriate to do this 6:1:1 reduction, or will that just reduce the color
> data even more than the YUV420 format already has?

You can easily make this configurable in tarkin.c, near line 191. Until 
now this was not necessairy...

Holger

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