From patchwork Sat May 9 09:04:47 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jacopo Mondi X-Patchwork-Id: 209884 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B0F6DC47254 for ; Sat, 9 May 2020 09:02:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9167624957 for ; Sat, 9 May 2020 09:02:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727909AbgEIJCJ (ORCPT ); Sat, 9 May 2020 05:02:09 -0400 Received: from relay5-d.mail.gandi.net ([217.70.183.197]:41317 "EHLO relay5-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725930AbgEIJCJ (ORCPT ); Sat, 9 May 2020 05:02:09 -0400 X-Originating-IP: 212.216.150.148 Received: from uno.homenet.telecomitalia.it (a-ur1-85.tin.it [212.216.150.148]) (Authenticated sender: jacopo@jmondi.org) by relay5-d.mail.gandi.net (Postfix) with ESMTPSA id CE4371C000A; Sat, 9 May 2020 09:02:02 +0000 (UTC) From: Jacopo Mondi To: linux-media@vger.kernel.org (open list:MEDIA INPUT INFRASTRUCTURE (V4L/DVB)), libcamera-devel@lists.libcamera.org, Mauro Carvalho Chehab , Hans Verkuil , Sakari Ailus , Laurent Pinchart Cc: Jacopo Mondi , tfiga@google.com, pavel@ucw.cz Subject: [PATCH v11 04/13] media: v4l2-ctrl: Document V4L2_CID_CAMERA_SENSOR_ROTATION Date: Sat, 9 May 2020 11:04:47 +0200 Message-Id: <20200509090456.3496481-5-jacopo@jmondi.org> X-Mailer: git-send-email 2.26.1 In-Reply-To: <20200509090456.3496481-1-jacopo@jmondi.org> References: <20200509090456.3496481-1-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 rotation correction to be applied to images before displaying them to the user. Signed-off-by: Jacopo Mondi --- .../media/v4l/ext-ctrls-camera.rst | 121 ++++++++++++++++++ 1 file changed, 121 insertions(+) diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-camera.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-camera.rst index 5d7fca799f2a8..d9a117f75c9c8 100644 --- a/Documentation/userspace-api/media/v4l/ext-ctrls-camera.rst +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-camera.rst @@ -540,6 +540,127 @@ enum v4l2_scene_mode - +``V4L2_CID_CAMERA_SENSOR_ROTATION (integer)`` + This read-only control describes the rotation correction in degrees in the + counter-clockwise direction to be applied to the captured images once + captured to memory to compensate for the camera sensor mounting rotation. + + For a precise definition of the sensor mounting rotation refer to the + extensive description of the 'rotation' properties in the device tree + bindings file 'video-interfaces.txt'. + + A few examples are below reported, using a shark swimming from left to + right in front of the user as the example scene to capture. :: + + 0 X-axis + 0 +-------------------------------------> + ! + ! + ! + ! |\____)\___ + ! ) _____ __`< + ! |/ )/ + ! + ! + ! + V + Y-axis + + Example one - Webcam + + Assuming you can bring your laptop with you while swimming with sharks, + the camera module of the laptop is installed on the user facing part of a + laptop screen casing, and is typically used for video calls. The captured + images are meant to be displayed in landscape mode (width > height) on the + laptop screen. + + The camera is typically mounted upside-down to compensate the lens optical + inversion effect. In this case the value of the + V4L2_CID_CAMERA_SENSOR_ROTATION control is 0, no rotation is required to + display images correctly to the user. + + If the camera sensor is not mounted upside-down it is required to compensate + the lens optical inversion effect and the value of the + V4L2_CID_CAMERA_SENSOR_ROTATION control is 180 degrees, as images will + result rotated when captured to memory. :: + + +--------------------------------------+ + ! ! + ! ! + ! ! + ! __/(_____/| ! + ! >.___ ____ ( ! + ! \( \| ! + ! ! + ! ! + ! ! + +--------------------------------------+ + + A software rotation correction of 180 degrees has to be applied to correctly + display the image on the user screen. :: + + +--------------------------------------+ + ! ! + ! ! + ! ! + ! |\____)\___ ! + ! ) _____ __`< ! + ! |/ )/ ! + ! ! + ! ! + ! ! + +--------------------------------------+ + + Example two - Phone camera + + It is more handy to go and swim with sharks with only your mobile phone + with you and take pictures with the camera that is installed on the back + side of the device, facing away from the user. The captured images are meant + to be displayed in portrait mode (height > width) to match the device screen + orientation and the device usage orientation used when taking the picture. + + The camera sensor is typically mounted with its pixel array longer side + aligned to the device longer side, upside-down mounted to compensate for + the lens optical inversion effect. + + The images once captured to memory will be rotated and the value of the + V4L2_CID_CAMERA_SENSOR_ROTATION will report a 90 degree rotation. :: + + + +-------------------------------------+ + | _ _ | + | \ / | + | | | | + | | | | + | | > | + | < | | + | | | | + | . | + | V | + +-------------------------------------+ + + A correction of 90 degrees in counter-clockwise direction has to be + applied to correctly display the image in portrait mode on the device + screen. :: + + +--------------------+ + | | + | | + | | + | | + | | + | | + | |\____)\___ | + | ) _____ __`< | + | |/ )/ | + | | + | | + | | + | | + | | + +--------------------+ + + .. [#f1] This control may be changed to a menu control in the future, if more options are required.