|author||Sakari Ailus <email@example.com>||2021-06-22 13:17:20 +0200|
|committer||Mauro Carvalho Chehab <firstname.lastname@example.org>||2021-08-04 14:43:50 +0200|
media: Documentation: v4l: Improve frame rate configuration documentation
Improve the documentation of the frame rate configuration so that it can be understood by a regular human being. Signed-off-by: Sakari Ailus <email@example.com> Signed-off-by: Mauro Carvalho Chehab <firstname.lastname@example.org>
Diffstat (limited to 'Documentation/userspace-api/media')
1 files changed, 10 insertions, 13 deletions
diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
index 2b5a13dc843f..b1c2ab2854af 100644
@@ -23,19 +23,7 @@ Image Process Control IDs
``V4L2_CID_LINK_FREQ (integer menu)``
- Data bus frequency. Together with the media bus pixel code, bus type
- (clock cycles per sample), the data bus frequency defines the pixel
- rate (``V4L2_CID_PIXEL_RATE``) in the pixel array (or possibly
- elsewhere, if the device is not an image sensor). The frame rate can
- be calculated from the pixel clock, image width and height and
- horizontal and vertical blanking. While the pixel rate control may
- be defined elsewhere than in the subdev containing the pixel array,
- the frame rate cannot be obtained from that information. This is
- because only on the pixel array it can be assumed that the vertical
- and horizontal blanking information is exact: no other blanking is
- allowed in the pixel array. The selection of frame rate is performed
- by selecting the desired horizontal and vertical blanking. The unit
- of this control is Hz.
+ The frequency of the data bus (e.g. parallel or CSI-2).
@@ -43,6 +31,15 @@ Image Process Control IDs
Pixel sampling rate in the device's pixel array. This control is
read-only and its unit is pixels / second.
+ Some devices use horizontal and vertical balanking to configure the frame
+ rate. The frame rate can be calculated from the pixel rate, analogue crop
+ rectangle as well as horizontal and vertical blanking. The pixel rate
+ control may be present in a different sub-device than the blanking controls
+ and the analogue crop rectangle configuration.
+ The configuration of the frame rate is performed by selecting the desired
+ horizontal and vertical blanking. The unit of this control is Hz.
Some capture/display/sensor devices have the capability to generate
test pattern images. These hardware specific test patterns can be