Video standards

[Pekka Paalanen]

On Thu, 28 Mar 2024 19:19:33 -0300
salsaman <salsaman at gmail.com> wrote:

> There are two hardware settings from the monitor that overlap video, these
> are
> - monitor aspect ratio
> - monitor pixel aspect ratio
> These are both useful when rendering video. The first defines how much
> stretch or letterbocing to apply, the second defines non square pixels,
> which is goof to know if you want to render fixed size objects (a circle
> for example). Knowing the monitor size in RGB or Y plane pixels can also be
> useful to define a max or min resize limit (whether it is min or max
> depends on the desired display quality level)

Thanks. I was trying to ask what kind of video standards you have
experience and expertise in?

I'm also interested in what kind of standards you see as missing. The
Wayland extension aims to cover everything display related. I'm sure
video file format specifications do their job.

What would be left to define?

What goals would there be?

I suppose individual APIs like Pipewire might be lacking something, but
that's a Pipewire API rather than an XDG standard. Or do we need an XDG
standard to be used as the design guide and reference for APIs?


Thanks,
pq

> On Thu, 28 Mar 2024 at 19:05, salsaman <salsaman at gmail.com> wrote:
> 
> > colour management and hdr mostly intersect with three areas of video:
> > pixel formats, yuv <-> rgb conversions and gamma transfer functions.
> > For example
> > xdg_pixformat_yuv121010
> > xdg_subspace_bt2020
> > xdg_gamma_bt2020
> >
> > just off the top of my head, these arent intended to be actual suggestions
> >
> >
> > On Thu, 28 Mar 2024 at 18:57, salsaman <salsaman at gmail.com> wrote:
> >  
> >> In addition, I am not sure if there are xdg standards for audio, but I
> >> would suggest video and follow similar hierarchies, and that both could be
> >> classed under a more generic xdg multimedia standard.
> >>
> >>
> >> On Thu, 28 Mar 2024 at 18:48, salsaman <salsaman at gmail.com> wrote:
> >>  
> >>> Hi, IMO hardware related would be more appropriate under display
> >>> standards
> >>> Video standards could be more software related, and provide common
> >>> definitions, for example , allowing exchange of information between
> >>> applications which produce or consume video frames or streams of frames.
> >>> Some examples I can think of might be
> >>>  xdg_colorspace_RGB,
> >>>  xdg_colorspace_YUV
> >>>
> >>> xdg_pixfmt_RGB24
> >>> xdg_pixfmt_YUV420p
> >>> etc
> >>>
> >>>  xdg_gamma_linear
> >>>  xdg_gamma_sRGB
> >>>
> >>> xdg_video_width
> >>> xdg_video_height
> >>>
> >>> I could provide a more full list, but I think if it goes along this
> >>> route. the starting point has to be what are we setting out to achieve with
> >>> the standards / definitions, and provide a range of speculative use cases.
> >>>
> >>> Gabriel (salsaman)
> >>>
> >>>
> >>> On Thu, 28 Mar 2024 at 06:07, Pekka Paalanen <  
> >>> pekka.paalanen at haloniitty.fi> wrote:  
> >>>  
> >>>> On Wed, 27 Mar 2024 11:45:00 -0300
> >>>> salsaman <salsaman at gmail.com> wrote:
> >>>>  
> >>>> > ISTR that the xdg video standards were never defined, If you need any
> >>>> > advice or assistance with this, I would be happy to act in an
> >>>> > advisory capacity if that is called for. I have over 20 years  
> >>>> experience of  
> >>>> > developing Free Software video and have been an active participant in
> >>>> > developing other video / effects standards. I have been a bit our of  
> >>>> the  
> >>>> > spotlight recently as I have been busy architecting and implementing  
> >>>> the  
> >>>> > core components of the upcoming next gen LiVES 4,0 video application  
> >>>> plus  
> >>>> > its accompanying state-of-the-art effects standard)  
> >>>>
> >>>> Hi,
> >>>>
> >>>> what kind of video standards would that be?
> >>>>
> >>>> I'm wondering if it would have anything to do with Wayland color
> >>>> management and HDR:
> >>>>
> >>>> https://gitlab.freedesktop.org/pq/color-and-hdr
> >>>>
> >>>> https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/183
> >>>>
> >>>> https://gitlab.freedesktop.org/wayland/wayland-protocols/-/merge_requests/14
> >>>>
> >>>> Would there need to be any XDG standards to support color managed HDR
> >>>> desktops, or is the window system support enough?
> >>>>
> >>>> I have not much in my mind, but then I've been staring only at the
> >>>> window system interactions, and haven't seen what else the desktop
> >>>> ecosystem or applications might need.
> >>>>
> >>>> Recommended display calibration and measurement procedures maybe?
> >>>>
> >>>> Desktop viewing environment standards?
> >>>>
> >>>> Viewing environment measurement?
> >>>>
> >>>> They could be as straightforward as referring to a freely available
> >>>> ITU-R or SMPTE papers or others, if there are suitable ones.
> >>>>
> >>>>
> >>>> Thanks,
> >>>> pq
> >>>>  
> >>>  

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