From patchwork Thu Oct 30 16:58:08 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= X-Patchwork-Id: 24917 Return-Path: X-Original-To: parsemail@patchwork.libcamera.org Delivered-To: parsemail@patchwork.libcamera.org Received: from lancelot.ideasonboard.com (lancelot.ideasonboard.com [92.243.16.209]) by patchwork.libcamera.org (Postfix) with ESMTPS id AD147C32D4 for ; Thu, 30 Oct 2025 16:58:44 +0000 (UTC) Received: from lancelot.ideasonboard.com (localhost [IPv6:::1]) by lancelot.ideasonboard.com (Postfix) with ESMTP id 5E54160A8B; Thu, 30 Oct 2025 17:58:44 +0100 (CET) Authentication-Results: lancelot.ideasonboard.com; dkim=pass (1024-bit key; unprotected) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="JDSNMdEJ"; dkim-atps=neutral Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647]) by lancelot.ideasonboard.com (Postfix) with ESMTPS id E0FEF608DE for ; Thu, 30 Oct 2025 17:58:24 +0100 (CET) Received: from pb-laptop.local (185.221.140.239.nat.pool.zt.hu [185.221.140.239]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id C46761E33; Thu, 30 Oct 2025 17:56:34 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1761843394; bh=k6ZRoM30ybTKu+WVfG0DyOfg43MBzqbd912GFVWQjkY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JDSNMdEJgntC51lXf2pA+mi/qIPBvfIgKRrmuM40pRSbkbFb9V29BQaIhNR6qJhBU QM10iBx2dXKzldXd1k62o3XojEdxgL87H7IFi+2lV/CLYhTb1LJI6ylNqqy3Vj3JwW cKt72jF7AROseW7bKdb8sZmBkOZ/WBIOzqqikzMw= From: =?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= To: libcamera-devel@lists.libcamera.org Cc: Jacopo Mondi , Paul Elder Subject: [RFC PATCH v3 14/22] libcamera: camera: Introduce metadataAvailable signal Date: Thu, 30 Oct 2025 17:58:08 +0100 Message-ID: <20251030165816.1095180-15-barnabas.pocze@ideasonboard.com> X-Mailer: git-send-email 2.51.1 In-Reply-To: <20251030165816.1095180-1-barnabas.pocze@ideasonboard.com> References: <20251030165816.1095180-1-barnabas.pocze@ideasonboard.com> MIME-Version: 1.0 X-BeenThere: libcamera-devel@lists.libcamera.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libcamera-devel-bounces@lists.libcamera.org Sender: "libcamera-devel" From: Jacopo Mondi Add a new signal to the Camera class that allows applications to receive notifications for early completion of metadata results. To avoid expensive copies of the metadata results the signal transports a view object of metadata items that are ready. The signal is an opt-in feature for applications and the sum of all metadata results notified through this signal is available in Request::metadata() at request completion time. Signed-off-by: Jacopo Mondi [Use `MetadataList::Diff`, change documentation accordingly.] Signed-off-by: Barnabás Pőcze Reviewed-by: Paul Elder Reviewed-by: Kieran Bingham --- Original: https://patchwork.libcamera.org/patch/22227/ --- include/libcamera/camera.h | 1 + src/libcamera/camera.cpp | 54 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 55 insertions(+) diff --git a/include/libcamera/camera.h b/include/libcamera/camera.h index 53089282a4..53f0485bc3 100644 --- a/include/libcamera/camera.h +++ b/include/libcamera/camera.h @@ -123,6 +123,7 @@ public: const std::string &id() const; + Signal metadataAvailable; Signal bufferCompleted; Signal requestCompleted; Signal<> disconnected; diff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp index 7bfa50b52c..a6d331a03c 100644 --- a/src/libcamera/camera.cpp +++ b/src/libcamera/camera.cpp @@ -911,6 +911,60 @@ const std::string &Camera::id() const return _d()->id_; } +/** + * \var Camera::metadataAvailable + * \brief Signal emitted when metadata for a request is available + * + * The metadataAvailable signal notifies applications about the availability + * of metadata for a request before the request completes. + * + * As metadata results could be large in size, the signal transports only a view + * object via which the newly completed metadata items can be accessed. Similarly + * to the metadata list itself, this object is thread-safe, and can be sent to other + * threads for deferred processing. The view object is valid until the request is + * destroyed or reused, whichever happens first. + * + * Applications can access the value of the newly available metadata results as follows: + * + * \code + + void metadataAvailableHandler(Request *request, MetadataList::Diff update) + { + // The object can be iterated... + for (auto &&[id, data] : update) { + // `id` is the numeric identifier + // `data` is a `ControlValueView` object + } + + // ...or individual items can be looked up. + if (auto x = update.get(controls::SensorTimestamp)) { + // `SensorTimestamp` will only be found if it is part of this + // particular update; metadata items completed earlier will + // not be found. + } + } + \endcode + * + * This signal is emitted multiple times for the same request, it is in fact + * emitted by libcamera every time a new set of metadata is made available + * by the Camera to the application. + * + * The sum of all metadata reported through this signal is equal to + * Request::metadata() list when the Request completes. + * + * Application can opt-in to handle this signal to receive fast notifications + * of metadata availability or can equally access the full metadata list + * at Request completion time through Request::metadata() if they have no interest + * in early metadata notification. + * + * \note The received MetadataList::Diff object is merely a view, it is only valid until + * the associated Request is destroyed or \ref Request::reuse() "reused". However, + * during its valid lifetime, an application is free to create copies and access the + * completed metadata items from separate threads by iteration or MetadataList::Diff::get(). + * + * \sa ControlValueView + */ + /** * \var Camera::bufferCompleted * \brief Signal emitted when a buffer for a request queued to the camera has