From patchwork Mon Oct 7 16:29:06 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jacopo Mondi X-Patchwork-Id: 11178063 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 61B371599 for ; Mon, 7 Oct 2019 16:27:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4A319206C0 for ; Mon, 7 Oct 2019 16:27:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728901AbfJGQ1r (ORCPT ); Mon, 7 Oct 2019 12:27:47 -0400 Received: from relay1-d.mail.gandi.net ([217.70.183.193]:45827 "EHLO relay1-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728862AbfJGQ1r (ORCPT ); Mon, 7 Oct 2019 12:27:47 -0400 X-Originating-IP: 2.224.242.101 Received: from uno.lan (2-224-242-101.ip172.fastwebnet.it [2.224.242.101]) (Authenticated sender: jacopo@jmondi.org) by relay1-d.mail.gandi.net (Postfix) with ESMTPSA id 1CA6C240010; Mon, 7 Oct 2019 16:27:43 +0000 (UTC) From: Jacopo Mondi To: Mauro Carvalho Chehab , Hans Verkuil , Sakari Ailus , Laurent Pinchart , tfiga@google.com, pavel@ucw.cz Cc: Jacopo Mondi , linux-media@vger.kernel.org (open list:MEDIA INPUT INFRASTRUCTURE (V4L/DVB)) Subject: [PATCH v4 04/11] media: v4l2-ctrl: Document V4L2_CID_CAMERA_SENSOR_ROTATION Date: Mon, 7 Oct 2019 18:29:06 +0200 Message-Id: <20191007162913.250743-5-jacopo@jmondi.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191007162913.250743-1-jacopo@jmondi.org> References: <20191007162913.250743-1-jacopo@jmondi.org> MIME-Version: 1.0 Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org 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 --- .../media/uapi/v4l/ext-ctrls-camera.rst | 116 ++++++++++++++++++ 1 file changed, 116 insertions(+) diff --git a/Documentation/media/uapi/v4l/ext-ctrls-camera.rst b/Documentation/media/uapi/v4l/ext-ctrls-camera.rst index b151c016256c..e1fee4814e5b 100644 --- a/Documentation/media/uapi/v4l/ext-ctrls-camera.rst +++ b/Documentation/media/uapi/v4l/ext-ctrls-camera.rst @@ -542,6 +542,122 @@ 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 for the + device 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. + + 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,num-col) + ! 1,0 1,1 1,2 ... + ! ... + ! ... + ! (num-lines,0)...(num-col,num-lines) + y V + + + Assuming pixels are scanned out from (0,0) to (num-lines,num-col) + progressively:: + + (0,0) ---->-------------> (0,num-col) + (1,0) ---->-------------> (1,num-col) + ( .... )-->-------------> ( .... ) + (num-lines,0)----------->(num-lines,num-col) + + + 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,num-col) ... ... (num-lines,num-col) + ! .... + ! 0,2 1,2 ... ... + ! 0,1 1,1 ... ... + ! 0,0 1,0 ... (num-lines,0) + (0,0)------------------------------------> + y + + And the pixel scan-out sequence would then proceed as follows starting + from pixel (0,0):: + + (0,num-col) (num-lines,num-col) + ^ ^ ^ ^ ^ + ! ! ! ! ! + ! ! ! ! ! + ! ! ! ! ! + ! ! ! ! ! + (0,0) (1,0).... (num-lines,0) + + Which when applied to the capture scene gives:: + + (0,num-col) (num-lines,num-col) + ^ ^ ^ ^ ^ + ! ! 0 ! ! + ! ! -|- ! ! + ! ! /!\ ! ! + ! ! ! ! ! + (0,0) (1,0).... (num-lines,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 + image when displayed on the screen. + + 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:: + + +------+ 90 degree counterclockwise + | o | mounting rotation applied + | -|- | along the axis directed + | / \ | away from the sensor lens + +------+ + | + V + +------+ + | \ ! | Resulting captured + | --0 | image when displayed + | / ! | on screen + +------+ + | + V + +------+ + | 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.