From patchwork Fri Aug 15 10:29:33 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Stefan Klug X-Patchwork-Id: 24123 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 1C947BDCC1 for ; Fri, 15 Aug 2025 10:30:33 +0000 (UTC) Received: from lancelot.ideasonboard.com (localhost [IPv6:::1]) by lancelot.ideasonboard.com (Postfix) with ESMTP id B8E53692CC; Fri, 15 Aug 2025 12:30:32 +0200 (CEST) Authentication-Results: lancelot.ideasonboard.com; dkim=pass (1024-bit key; unprotected) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="H512Q9Kf"; 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 7D28F692CA for ; Fri, 15 Aug 2025 12:30:31 +0200 (CEST) Received: from ideasonboard.com (unknown [IPv6:2a00:6020:448c:6c00:83d1:ae5d:93a6:6837]) by perceval.ideasonboard.com (Postfix) with UTF8SMTPSA id 9E26856D; Fri, 15 Aug 2025 12:29:36 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1755253776; bh=Tlclys7StzvIVHcL4hYYAMxSyv/SvqVCejl9QGER+cg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=H512Q9KfrtZtex11Vbx6wW9KI2MWva5u2HRszzvg1yt7zN4R4cKeoVrw1UUCTqNmc g3tr6BX4wxxs+ynytTlDyAmlcIqRpGLfTVN+KBpoZ9K4lLvszE6oyNMehkQi7C+iLd Q1Cq5cskTkJkX1ugMXPJvYmDuprbdU2/H5XCinck= From: Stefan Klug To: libcamera-devel@lists.libcamera.org Cc: Stefan Klug , Paul Elder Subject: [PATCH v3 13/19] ipa: rkisp1: Switch histogram to RGB combined mode Date: Fri, 15 Aug 2025 12:29:33 +0200 Message-ID: <20250815102945.1602071-14-stefan.klug@ideasonboard.com> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250815102945.1602071-1-stefan.klug@ideasonboard.com> References: <20250815102945.1602071-1-stefan.klug@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" The Y mode of the histogram gets captured at the ISP output, before the output formatter. This has the side effect that the first and the last bins are empty in case of limited YUV range. Another side effect is that gamma and GWDR processing is included in the histogram which makes algorithm development very difficult. In RGB mode the histogram is taken after xtalk (CCM) and is therefore independent of gamma and WDR. The limited range issue also does not apply. In the ISP reference it is however stated that "it is not possible to calculate a luminance or grayscale histogram from an RGB histogram since the position information is lost during its generation". During testing the RGB histogram provided good data and better algorithmic stability at a possible (but not measured) inaccuracy. Another option would be to pass the color space information into the IPA and strip the histogram accordingly. For ease of implementation switch to the RGB mode. Signed-off-by: Stefan Klug Reviewed-by: Paul Elder Reviewed-by: Kieran Bingham --- Changes in v3: - Added block comment inside the code --- src/ipa/rkisp1/algorithms/agc.cpp | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/src/ipa/rkisp1/algorithms/agc.cpp b/src/ipa/rkisp1/algorithms/agc.cpp index d34c041f9fe1..ba617a4e6e0c 100644 --- a/src/ipa/rkisp1/algorithms/agc.cpp +++ b/src/ipa/rkisp1/algorithms/agc.cpp @@ -396,7 +396,24 @@ void Agc::prepare(IPAContext &context, const uint32_t frame, hstConfig.setEnabled(true); hstConfig->meas_window = context.configuration.agc.measureWindow; - hstConfig->mode = RKISP1_CIF_ISP_HISTOGRAM_MODE_Y_HISTOGRAM; + /** + * The Y mode of the histogram gets captured at the ISP output, before + * the output formatter. This has the side effect that the first and + * the last bins are empty in case of limited YUV range. Another side + * effect is that gamma and GWDR processing is included in the histogram + * which makes algorithm development very difficult. In RGB mode the + * histogram is taken after xtalk (CCM) and is therefore independent of + * gamma and WDR. The limited range issue also does not apply. In the + * ISP reference it is however stated that "it is not possible to + * calculate a luminance or grayscale histogram from an RGB histogram + * since the position information is lost during its generation". + * + * During testing the RGB histogram provided good data and better + * algorithmic stability at a possible (but not measured) inaccuracy. + * + * \todo For a proper fix support for HIST64 is needed. + */ + hstConfig->mode = RKISP1_CIF_ISP_HISTOGRAM_MODE_RGB_COMBINED; Span weights{ hstConfig->hist_weight,