[vlc-devel] [PATCH 1/3] picture: round visible pitch/line to the upper integer

[Steve Lhomme]

On Wed, Mar 22, 2017 at 5:01 PM, Rémi Denis-Courmont <remi at remlab.net> wrote:
> Le keskiviikkona 22. maaliskuuta 2017, 16.50.49 EET Steve Lhomme a écrit :
>> From: Steve Lhomme <robUx4 at videolabs.io>
>>
>> Otherwise in cases where there's pixel sub-sampling we may miss some visible
>> sub pixels.
>
> I am not sure that this is correct. While it is annoying to handle, it is not
> necessarily incorrect for the visible dimensions to not follow macropixel
> boundaries.

Let's say you have a I420 of 3x3 visible pixels. The Y plane is 3x3 of
visible pixels. The U and V planes can either be 1x1 or 2x2 visible
pixels. In the first case you will be constructing the last row with
pixels that are not meant to be visible and so possibly not copied
(most plane copies only copy the visible lines, no more). This seems
bogus to me. The 2x2 pixels are actually data that should be filled by
the decoder with data that were actually encoded.

> --
> 雷米‧德尼-库尔蒙
> https://www.remlab.net/
>
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