Commit 7b575b6d authored Dec 02, 2019 by Hans Verkuil Committed by Mauro Carvalho Chehab Dec 13, 2019

media: vidioc-g-dv-timings.rst: fix wrong porch



It is the vfrontporch of field 1 that is one half-line longer,
not the backporch.

The order of the vertical signals in an interlaced system is:

Field 1:

vsync
vbackporch
active video of field 1
vfrontporch + 0.5

Field 2:

il_vsync
il_vbackporch - 0.5
active video of field 2
il_vfrontporch

Interlaced systems that use HALF_LINE set the il_ fields as follows:

il_vfrontporch = vfrontporch
il_vsync = vsync
il_vbackporch = vbackporch + 1

So the total vertical blanking for field 1 is:

	vsync + vbackporch + vfrontporch + 0.5

and for field 2:

	vsync + vbackporch + 1 + vfrontporch - 0.5 ==
	vsync + vbackporch + vfrontporch + 0.5

So each field has the same number of half-lines.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

parent 3d15c764

Documentation/media/uapi/v4l/vidioc-g-dv-timings.rst

+1 −1

Original line number	Diff line number	Diff line
		@@ -279,7 +279,7 @@ EBUSY
		then it will set this flag to signal this to the application.
		* - ``V4L2_DV_FL_HALF_LINE``
		- Specific to interlaced formats: if set, then the vertical
		backporch of field 1 (aka the odd field) is really one half-line
		frontporch of field 1 (aka the odd field) is really one half-line
		longer and the vertical backporch of field 2 (aka the even field)
		is really one half-line shorter, so each field has exactly the
		same number of half-lines. Whether half-lines can be detected or