[vlc-devel] Minor wiki updates

[Juha Jeronen]

On 01/27/2012 09:19 PM, Rémi Denis-Courmont wrote:
> Le vendredi 27 janvier 2012 21:09:04 Rémi Denis-Courmont, vous avez écrit :
>> Le vendredi 27 janvier 2012 12:27:11 Juha Jeronen, vous avez écrit :
>>> Hi all,
>>>
>>> Added description of J420 and J422 formats:
>>> http://wiki.videolan.org/YUV
>> I edited a bit and hopefully improved the grammar. I also removed the dummy
>> wiki-links to self.
>>
>> I also detailled the order of lumas in YUYV and UYVY. But now I am having
>> second thoughts  on YVYU and VYUV. I would think they are caused by
>> mismatched endian electronics, thus actually Y2-V-Y1-U and V-Y2-U-Y1,
>> right?
> But the V4L2 specification and our chroma code does it the other way, the 
> natural order: Y1-V-Y2-U. Confusing.

Wouldn't be surprised if it was defined that way. A lot of things in
video don't really make sense :)

(For example, what to make of YV12? As in, why would anyone want the U/V
planes in reverse order?

For another example, interlaced encoding and 4:2:0 chroma. In an
interlaced picture with half-vertical-resolution chroma, the only
sensible way is that e.g. the zeroth chroma line belongs to luma lines 0
and 2, and the first (next) chroma line to luma lines 1 and 3. However,
when I was hacking the deinterlacer, I seem to recall that chroma line 0
got paired with luma lines 0 and 1, as if the picture was progressive.
But I'd have to investigate again to be completely sure as it's been
some time.)

 -J