{"id":24917,"url":"https://patchwork.libcamera.org/api/1.1/patches/24917/?format=json","web_url":"https://patchwork.libcamera.org/patch/24917/","project":{"id":1,"url":"https://patchwork.libcamera.org/api/1.1/projects/1/?format=json","name":"libcamera","link_name":"libcamera","list_id":"libcamera_core","list_email":"libcamera-devel@lists.libcamera.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20251030165816.1095180-15-barnabas.pocze@ideasonboard.com>","date":"2025-10-30T16:58:08","name":"[RFC,v3,14/22] libcamera: camera: Introduce metadataAvailable signal","commit_ref":null,"pull_url":null,"state":"superseded","archived":false,"hash":"0cf7b79ece7d63ff580dc30c3e41f509d694ae2e","submitter":{"id":216,"url":"https://patchwork.libcamera.org/api/1.1/people/216/?format=json","name":"Barnabás Pőcze","email":"barnabas.pocze@ideasonboard.com"},"delegate":null,"mbox":"https://patchwork.libcamera.org/patch/24917/mbox/","series":[{"id":5545,"url":"https://patchwork.libcamera.org/api/1.1/series/5545/?format=json","web_url":"https://patchwork.libcamera.org/project/libcamera/list/?series=5545","date":"2025-10-30T16:57:54","name":"libcamera: Add `MetadataList`","version":3,"mbox":"https://patchwork.libcamera.org/series/5545/mbox/"}],"comments":"https://patchwork.libcamera.org/api/patches/24917/comments/","check":"pending","checks":"https://patchwork.libcamera.org/api/patches/24917/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id AD147C32D4\n\tfor ;\n\tThu, 30 Oct 2025 16:58:44 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 5E54160A8B;\n\tThu, 30 Oct 2025 17:58:44 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id E0FEF608DE\n\tfor ;\n\tThu, 30 Oct 2025 17:58:24 +0100 (CET)","from pb-laptop.local (185.221.140.239.nat.pool.zt.hu\n\t[185.221.140.239])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id C46761E33;\n\tThu, 30 Oct 2025 17:56:34 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"JDSNMdEJ\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1761843394;\n\tbh=k6ZRoM30ybTKu+WVfG0DyOfg43MBzqbd912GFVWQjkY=;\n\th=From:To:Cc:Subject:Date:In-Reply-To:References:From;\n\tb=JDSNMdEJgntC51lXf2pA+mi/qIPBvfIgKRrmuM40pRSbkbFb9V29BQaIhNR6qJhBU\n\tQM10iBx2dXKzldXd1k62o3XojEdxgL87H7IFi+2lV/CLYhTb1LJI6ylNqqy3Vj3JwW\n\tcKt72jF7AROseW7bKdb8sZmBkOZ/WBIOzqqikzMw=","From":"=?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= ","To":"libcamera-devel@lists.libcamera.org","Cc":"Jacopo Mondi ,\n\tPaul Elder ","Subject":"[RFC PATCH v3 14/22] libcamera: camera: Introduce metadataAvailable\n\tsignal","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","Content-Type":"text/plain; charset=UTF-8","Content-Transfer-Encoding":"8bit","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "},"content":"From: Jacopo Mondi \n\nAdd a new signal to the Camera class that allows applications to\nreceive notifications for early completion of metadata results.\n\nTo avoid expensive copies of the metadata results the signal\ntransports a view object of metadata items that are ready.\n\nThe signal is an opt-in feature for applications and the sum of\nall metadata results notified through this signal is available\nin Request::metadata() at request completion time.\n\nSigned-off-by: Jacopo Mondi \n[Use `MetadataList::Diff`, change documentation accordingly.]\nSigned-off-by: Barnabás Pőcze \nReviewed-by: Paul Elder \n---\nOriginal: https://patchwork.libcamera.org/patch/22227/\n---\n include/libcamera/camera.h | 1 +\n src/libcamera/camera.cpp | 54 ++++++++++++++++++++++++++++++++++++++\n 2 files changed, 55 insertions(+)","diff":"diff --git a/include/libcamera/camera.h b/include/libcamera/camera.h\nindex 53089282a4..53f0485bc3 100644\n--- a/include/libcamera/camera.h\n+++ b/include/libcamera/camera.h\n@@ -123,6 +123,7 @@ public:\n \n \tconst std::string &id() const;\n \n+\tSignal metadataAvailable;\n \tSignal bufferCompleted;\n \tSignal requestCompleted;\n \tSignal<> disconnected;\ndiff --git a/src/libcamera/camera.cpp b/src/libcamera/camera.cpp\nindex 7bfa50b52c..a6d331a03c 100644\n--- a/src/libcamera/camera.cpp\n+++ b/src/libcamera/camera.cpp\n@@ -911,6 +911,60 @@ const std::string &Camera::id() const\n \treturn _d()->id_;\n }\n \n+/**\n+ * \\var Camera::metadataAvailable\n+ * \\brief Signal emitted when metadata for a request is available\n+ *\n+ * The metadataAvailable signal notifies applications about the availability\n+ * of metadata for a request before the request completes.\n+ *\n+ * As metadata results could be large in size, the signal transports only a view\n+ * object via which the newly completed metadata items can be accessed. Similarly\n+ * to the metadata list itself, this object is thread-safe, and can be sent to other\n+ * threads for deferred processing. The view object is valid until the request is\n+ * destroyed or reused, whichever happens first.\n+ *\n+ * Applications can access the value of the newly available metadata results as follows:\n+ *\n+ * \\code\n+\n+\tvoid metadataAvailableHandler(Request *request, MetadataList::Diff update)\n+\t{\n+\t\t// The object can be iterated...\n+\t\tfor (auto &&[id, data] : update) {\n+\t\t\t// `id` is the numeric identifier\n+\t\t\t// `data` is a `ControlValueView` object\n+\t\t}\n+\n+\t\t// ...or individual items can be looked up.\n+\t\tif (auto x = update.get(controls::SensorTimestamp)) {\n+\t\t\t// `SensorTimestamp` will only be found if it is part of this\n+\t\t\t// particular update; metadata items completed earlier will\n+\t\t\t// not be found.\n+\t\t}\n+\t}\n+ \\endcode\n+ *\n+ * This signal is emitted multiple times for the same request, it is in fact\n+ * emitted by libcamera every time a new set of metadata is made available\n+ * by the Camera to the application.\n+ *\n+ * The sum of all metadata reported through this signal is equal to\n+ * Request::metadata() list when the Request completes.\n+ *\n+ * Application can opt-in to handle this signal to receive fast notifications\n+ * of metadata availability or can equally access the full metadata list\n+ * at Request completion time through Request::metadata() if they have no interest\n+ * in early metadata notification.\n+ *\n+ * \\note The received MetadataList::Diff object is merely a view, it is only valid until\n+ * the associated Request is destroyed or \\ref Request::reuse() \"reused\". However,\n+ * during its valid lifetime, an application is free to create copies and access the\n+ * completed metadata items from separate threads by iteration or MetadataList::Diff::get().\n+ *\n+ * \\sa ControlValueView\n+ */\n+\n /**\n * \\var Camera::bufferCompleted\n * \\brief Signal emitted when a buffer for a request queued to the camera has\n","prefixes":["RFC","v3","14/22"]}