[vlc-devel] [PATCH 3/12] esformat: fix ORIENT_LEFT_BOTTOM and ORIENT_RIGHT_TOP descriptions

[Romain Vimont]

On Sat, Sep 26, 2020 at 06:04:03PM +0300, Rémi Denis-Courmont wrote:
> Le lauantaina 26. syyskuuta 2020, 13.48.59 EEST Romain Vimont a écrit :
> > On Thu, Sep 24, 2020 at 11:29:58PM +0100, Lyndon Brown wrote:
> > > From: Lyndon Brown <jnqnfe at gmail.com>
> > > Date: Sun, 7 Jan 2018 19:22:38 +0000
> > > Subject: esformat: fix ORIENT_LEFT_BOTTOM and ORIENT_RIGHT_TOP
> > > descriptions
> > > 
> > > They had 90 degree clockwise / anti-clockwise rotation the wrong way
> > > around.
> > > 
> > > diff --git a/include/vlc_es.h b/include/vlc_es.h
> > > index a7af6c118c..841fa05bf6 100644
> > > --- a/include/vlc_es.h
> > > +++ b/include/vlc_es.h
> > > @@ -181,8 +181,8 @@ typedef enum video_orientation_t
> > > 
> > >      ORIENT_BOTTOM_LEFT, /**< Flipped vertically */
> > >      ORIENT_BOTTOM_RIGHT, /**< Rotated 180 degrees */
> > >      ORIENT_LEFT_TOP, /**< Transposed */
> > > 
> > > -    ORIENT_LEFT_BOTTOM, /**< Rotated 90 degrees clockwise */
> > > -    ORIENT_RIGHT_TOP, /**< Rotated 90 degrees anti-clockwise */
> > > +    ORIENT_LEFT_BOTTOM, /**< Rotated 90 degrees anti-clockwise */
> > > +    ORIENT_RIGHT_TOP, /**< Rotated 90 degrees clockwise */
> > 
> > I think is was correct before the patch:
> > 
> > ORIENT_LEFT_BOTTOM: top line represents LEFT, left column BOTTOM.
> 
> Left-bottom means the top row is stored in the left column and the left column 
> is stored in the bottom row.

This is not what I understand from the comment:

> ORIENT_TOP_LEFT = 0, /**< Top line represents top, left column left. */)

(the fact that this comment applies on a NORMAL orientation does not
help)

There are two sources of confusions for me.

Does video_orientation_t represent:
 1. how the image has been rotated before storage, or
 2. how the stored data must be rotated for display?

What is the meaning of ORIENT_XXX_YYY?
 A. the top row in memory represents the XXX of the picture,
    the left column in memory represents the YYY of the picture, or
 B. the top row of the picture is stored in the XXX in memory,
    the left column of the picture is stored in the YYY in memory?

What is the expected video_orientation_t for this example?

        capture    storage    display
         A---B      D---A      A---B
         |   | ---> |   | ---> |   |
         D---C      C---B      D---C

Regards