Re: [PATCH 0/2] drm/sti: support of interlaced content with Bottom Field

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Feb 12, 2016 at 10:26:03AM +0100, Vincent Abriou wrote:
> Interlaced video can have different scan order:
> Top Field First or Bottom Field First
> 
> In case of video with interlaced content, this information should be
> propagated from the userland to the DRM kernel driver that will process the
> deinterlacing starting with the top or the bottom field first.
> That's why we introduce this new flag definition DRM_MODE_FB_BFF (Bottom Field
> First) that should be used jointly with the already existing
> DRM_MODE_FB_INTERLACED flag incase of interlaced video with Bottom Field First
> scan order should be processed.

The way I envisioned this long ago is that we would specify the
bff/tff at flip time. In fact we already have the
DRM_MODE_PRESENT_TOP_FIELD/DRM_MODE_PRESENT_BOTTOM_FIELD flags for
setplane. When doing bob deinterlacing these would choose the field
we're going to present, and when doing interlaced scanout these would
choose tff vs. bff. But that approach does fall short with atomic when
you want to flip multiple planes at once.

One problem I see with making this part of the FB is that if you already
missed your original deadline for the first field, and you want to
actually present the second field instead, you're forced to create
another fb. So a plane property might be a bit more flexible. And the
same way as the setplane flags we could then share the properties for
bob deinterlacing field selection as well. There's no way to do bob
deinterlacing with fb flags, unless you create a separate fb for each
field.

-- 
Ville Syrjälä
Intel OTC
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