Hi Hans, On Fri, Sep 13, 2019 at 08:49:06PM +0200, Jacopo Mondi wrote: > Hi Hans, > > On Fri, Sep 13, 2019 at 04:02:45PM +0200, Hans Verkuil wrote: > > On 9/12/19 10:10 PM, Jacopo Mondi wrote: > > > Add documentation for the V4L2_CID_CAMERA_SENSOR_ROTATION camera > > > control. The newly added read-only control reports the camera device > > > mounting rotation. > > > > > > Signed-off-by: Jacopo Mondi <jacopo@xxxxxxxxxx> > > > --- > > > .../media/uapi/v4l/ext-ctrls-camera.rst | 117 ++++++++++++++++++ > > > 1 file changed, 117 insertions(+) > > > > > > diff --git a/Documentation/media/uapi/v4l/ext-ctrls-camera.rst b/Documentation/media/uapi/v4l/ext-ctrls-camera.rst > > > index f879dcc9409c..74991522ca3a 100644 > > > --- a/Documentation/media/uapi/v4l/ext-ctrls-camera.rst > > > +++ b/Documentation/media/uapi/v4l/ext-ctrls-camera.rst > > > @@ -542,6 +542,123 @@ enum v4l2_scene_mode - > > > > > > > > > > > > +``V4L2_CID_CAMERA_SENSOR_ROTATION (integer)`` > > > + This read-only control describes the sensor orientation expressed as > > > + rotation in counterclockwise degrees along the axis perpendicular to the > > > + device mounting plane, and directed away from the sensor lens. Possible > > > + values for the control are 90, 180 and 270 degrees. To compensate the device > > > > compensate -> compensate for > > > > > + mounting rotation on the captured images, a rotation of the same amount of > > > + degrees, in the same counterclockwise rotation direction should be applied > > > + along the axis directed from the observer to the captured image when > > > + displayed on a screen. > > > > Is this right? Shouldn't that be "in the clockwise direction"? If the sensor is > > mounted 90 degrees counterclockwise, then I need to rotate by 90 degrees clockwise > > to compensate for that, right? > > > > It really depend along which axis direction you are applying the mounting > rotation and the compensation rotation... See below... > > > > + > > > + To better understand the effect of the sensor rotation on the acquired > > > + images when displayed on a screen, it is helpful to consider a fictional > > > + scan-out sequence of the sensor's pixels, assuming the pixel array having > > > + its top-left pixel at position (0, 0) with values on the 'x' axis increasing > > > + towards the right direction, and values on the 'y' axis increasing towards > > > + the bottom. The effect of sensor rotation could be easily visualized > > > + considering the sequence of captured pixels. > > > + > > > + Assuming the following scene has to be captured:: > > > + > > > + o > > > + -|- > > > + / \ > > > + > > > + An upright mounted sensor has its pixel array displaced as follow:: > > > + > > > + x > > > + (0,0)----------------------> > > > + ! 0,0 0,1 0,2 ... 0,line-len > > > > Isn't that 0,0 ... 0,num-col? > > Yes indeed sorry > > > line-len is a weird name, shouldn't that be num-lines? > > > > line-len sounds like it is the same as num-col. > > > > I'm totally confused. > > > > num-col is totally wrong, that should have been num-lines > > In general > s/line-len/num-col > s/num-col/num-lines > > > > + ! 1,0 1,1 1,2 ... > > > + ! ... > > > + ! ... > > > + ! (num-col,0)... (num-col,line-len) > > > + y V > > > + > > > + > > > + Assuming pixels are scanned out from (0,0) to (num-col,line-len) > > > + progressively:: > > > + > > > + (0,0) ---->-------------> (0,line-len)---! > > > + !------------------------------------<a--! > > > + V > > > + (1,0) ---->-------------> (1,line-len)---! > > > + !------------------------------------<---! > > > + V > > > + (...) .-->--------------> ( ,,,, ) ---! > > > + !------------------------------------<---! > > > + V > > > + (num-col,0)------------->(num-col,line-len) > > > + > > > + > > > + If a rotation of 90 degrees counterclockwise along the axis perpendicular to > > > + the sensor's lens and directed towards the scene to be captured is applied > > > + to the sensor, the pixel array would then be rotated as follows:: > > > + > > > + x ^ 0,line-len,,,(num-col,line-len > > > + ! .... > > > + ! 0,2 1,2 ... > > > + ! 0,1 1,1 ... > > > + ! 0,0 1,0 ... num-col,0 > > > + (0,0)------------------------> > > > + y > > > + > > > + And the pixel scan-out sequence would then proceed as follows:: > > > + > > > + (0,line-len) (num-cols,line-len) > > > + ^\ ^\ ^\ ^\ ^ > > > + ! \ ! \ ! \ ! \ ! > > > + ! \ ! \ ! \ ! \ ! > > > + ! \ ! \ ! \ ! \ ! > > > + ! \! \! \! \! > > > + (0,0) (1,0) .... (num-cols,0) > > > + > > > + Which when applied to the capture scene gives:: > > > + > > > + (0,line-len) (num-cols,line-len) > > > + ^\ ^\ ^\ ^\ ^ > > > + ! \ ! \ 0 \ ! \ ! > > > + ! \ ! \ -|- \ ! \ ! > > > + ! \ ! / \ \ ! \ ! > > > + ! \! \! \! \! > > > + (0,0) (1,0) .... (num-cols,0) > > > + > > > + Producing the following image once captured to memory and > > > + displayed to the user:: > > > + > > > + \ ! > > > + --0 > > > + / ! > > > + > > > + Which has a rotation of the same amount of degrees applied on the opposite > > > + rotation direction along the axis that goes from the observer to the > > > + displayed image. > > > + > > > + In order to compensate the sensor mounting rotation, when expressed > > > + as counterclockwise rotation along the axis directed from the sensor to > > > + the captured scene, a rotation of the same amount of degrees in the > > > + same counterclockwise rotation direction but applied along the axis > > > + directed from the observer to the captured image, has to be applied.:: > > > > .:: -> : > > > > Don't I need the :: to mark the following block of text as verbatim ? > > > > + > > > + ------- 90 degree counterclockwise > > > + | o | mounting rotation applied > > > + | -|- | along the axis directed > > > + | / \ | away from the sensor lens > > > + ------- > > > + ------- > > > + | \ ! | Resulting captured > > > + | --0 | image when displayed > > > + | / ! | on screen > > > + ------- > > > > Trying this with my webcam turning it 90 degrees counterclockwise, I > > and up with my head to the left, not to the right. > > > > Along which axis direction are you rotating the camera counterclockwise ? > > If you see your face, and you rotate the camera counterclockwise while > looking at it, you're actually rotating along the axis directed -towards- > the sensor. > > The rotation here in the example and in the 'rotation' property > description has to be applied along the axis pointing aways from the > sensor, so what you're actually doing is rotating clockwise along that > direction (I guess)... So yes, to compensate that, you need to rotate > clockwise when you look at the image on the screen... Confusing, > right? > Does it work for you? Can I send a new iteration with your comments on the previous patches taken in ? Thanks j > > > + ------- > > > + | o | Rotation compensation > > > + | -|- | is 90 degrees counterclockwise > > > + | / \ | along the axis directed to the > > > + ------- displayed image > > > + > > > + > > > .. [#f1] > > > This control may be changed to a menu control in the future, if more > > > options are required. > > > > > > > Regards, > > > > Hans
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