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media: vidioc-g-dv-timings.rst: document V4L2_DV_FL_CAN_DETECT_REDUCED_FPS 

Document the new V4L2_DV_FL_CAN_DETECT_REDUCED_FPS flag and
update the V4L2_DV_FL_REDUCED_FPS description since it can now
also be used with receivers.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
This commit is contained in:
Hans Verkuil 2018-08-15 09:10:59 -04:00 committed by Mauro Carvalho Chehab
parent fb98e29ff1
commit a125385c9b
1 changed files with 19 additions and 8 deletions
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27
Documentation/media/uapi/v4l/vidioc-g-dv-timings.rst
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@ -257,14 +257,19 @@ EBUSY
will also be cleared. This is a read-only flag, applications must
not set this.
* - ``V4L2_DV_FL_REDUCED_FPS``
- CEA-861 specific: only valid for video transmitters, the flag is
cleared by receivers. It is also only valid for formats with the
``V4L2_DV_FL_CAN_REDUCE_FPS`` flag set, for other formats the
flag will be cleared by the driver. If the application sets this
flag, then the pixelclock used to set up the transmitter is
divided by 1.001 to make it compatible with NTSC framerates. If
the transmitter can't generate such frequencies, then the flag
will also be cleared.
- CEA-861 specific: only valid for video transmitters or video
receivers that have the ``V4L2_DV_FL_CAN_DETECT_REDUCED_FPS``
set. This flag is cleared otherwise. It is also only valid for
formats with the ``V4L2_DV_FL_CAN_REDUCE_FPS`` flag set, for other
formats the flag will be cleared by the driver.
If the application sets this flag for a transmitter, then the
pixelclock used to set up the transmitter is divided by 1.001 to
make it compatible with NTSC framerates. If the transmitter can't
generate such frequencies, then the flag will be cleared.
If a video receiver detects that the format uses a reduced framerate,
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
@ -294,3 +299,9 @@ EBUSY
- If set, then the hdmi_vic field is valid and contains the Video
Identification Code as per the HDMI standard (HDMI Vendor Specific
InfoFrame).
* - ``V4L2_DV_FL_CAN_DETECT_REDUCED_FPS``
- CEA-861 specific: only valid for video receivers, the flag is
cleared by transmitters.
If set, then the hardware can detect the difference between
regular framerates and framerates reduced by 1000/1001. E.g.:
60 vs 59.94 Hz, 30 vs 29.97 Hz or 24 vs 23.976 Hz.