Hi Hans, On Thursday 22 August 2013 08:56:00 Hans Verkuil wrote: > On 08/21/2013 11:58 PM, Laurent Pinchart wrote: > > On Monday 12 August 2013 12:58:32 Hans Verkuil wrote: > >> From: Hans Verkuil <hans.verkuil@xxxxxxxxx> > >> > >> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx> > >> --- > >> > >> Documentation/DocBook/media/v4l/v4l2.xml | 2 + > >> .../DocBook/media/v4l/vidioc-g-matrix.xml | 115 +++++++++++++ > >> .../DocBook/media/v4l/vidioc-query-matrix.xml | 178 +++++++++++++++ > >> 3 files changed, 295 insertions(+) > >> create mode 100644 Documentation/DocBook/media/v4l/vidioc-g-matrix.xml > >> create mode 100644 > >> Documentation/DocBook/media/v4l/vidioc-query-matrix.xml > > > > [snip] > > > >> diff --git a/Documentation/DocBook/media/v4l/vidioc-query-matrix.xml > >> b/Documentation/DocBook/media/v4l/vidioc-query-matrix.xml new file mode > >> 100644 > >> index 0000000..c2845c7 > >> --- /dev/null > >> +++ b/Documentation/DocBook/media/v4l/vidioc-query-matrix.xml [snip] > >> + <table pgwide="1" frame="none" id="v4l2-matrix-type"> > >> + <title>Matrix Types</title> > >> + <tgroup cols="2" align="left"> > >> + <colspec colwidth="30*" /> > >> + <colspec colwidth="55*" /> > >> + <thead> > >> + <row> > >> + <entry>Type</entry> > >> + <entry>Description</entry> > >> + </row> > >> + </thead> > >> + <tbody valign="top"> > >> + <row> > >> + <entry><constant>V4L2_MATRIX_T_MD_REGION</constant></entry> > >> + <entry>Hardware motion detection often divides the image into > >> several > >> + regions, and each region can have its own motion detection > >> thresholds. > >> + This matrix assigns a region number to each element. Each element > >> is > >> a __u8. > >> + Generally each element refers to a block of pixels in the image. > > > > From the description I have trouble understanding what the matrix type is > > for. Do you think we could make the explanation more detailed ? > > How about this: > > Hardware motion detection divides the image up into cells. If the image > resolution is WxH and the matrix size is COLSxROWS, then each cell is a > rectangle of (W/COLS)x(H/ROWS) pixels (approximately as there may be some > rounding involved). Depending on the hardware each cell can have its own > properties. This matrix type sets the 'region' property which is a __u8. > Each region will typically have its own set of motion detection parameters > such as a threshold that determines the motion detection sensitivity. By > assigning each cell a region you can create regions with lower and regions > with higher motion sensitivity. That sounds good to me. One more question, however: if the hardware divides the sub-sampled image into regions, how do you configure per-region thresholds ? The V4L2_MATRIX_T_MD_THRESHOLD matrix only configures per-cell thresholds. > > > + </entry> > > > + </row> > > > + <row> > > > + <entry><constant>V4L2_MATRIX_T_MD_THRESHOLD</constant></entry> > > > + <entry>Hardware motion detection can assign motion detection > > > threshold + values to each element of an image. Each element is a > > > __u16. + Generally each element refers to a block of pixels in > > > the image. > This would be improved as well along the same lines: > > Hardware motion detection divides the image up into cells. If the image > resolution is WxH and the matrix size is COLSxROWS, then each cell is a > rectangle of (W/COLS)x(H/ROWS) pixels (approximately as there may be some > rounding involved). Depending on the hardware each cell can have its own > motion detection sensitivity threshold. This matrix type sets the motion > detection threshold property which is a __u16. > > > + </entry> > > > + </row> > > > + </tbody> > > > + </tgroup> > > > + </table> > > > + > > > + </refsect1> > > > + <refsect1> > > > + &return-value; > > > + </refsect1> > > > +</refentry> -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
