[{"id":32267,"web_url":"https://patchwork.libcamera.org/comment/32267/","msgid":"<87zflvfqvw.fsf@redhat.com>","date":"2024-11-19T10:40:35","subject":"Re: [PATCH v3 17/17] ipa: rkisp1: awb: Expand comment","submitter":{"id":177,"url":"https://patchwork.libcamera.org/api/people/177/","name":"Milan Zamazal","email":"mzamazal@redhat.com"},"content":"Hi Laurent,\n\nthank you for the patch, such a clarification is always good.\n\nLaurent Pinchart writes:\n\n> The RGB to YCbCr conversion matrix mentioned in a comment, coming from\n> the hardware documentation, does not match any of the canonical matrices\n> specified by any standard. While researching where the values came from,\n> it became apparent they are likely Bt.601 limited range coefficients\n> rounded to 6 bits of decimal precision. Record this in comments.\n>\n> Signed-off-by: Laurent Pinchart \n\nReviewed-by: Milan Zamazal \n\n> ---\n> src/ipa/rkisp1/algorithms/awb.cpp | 13 +++++++++----\n> 1 file changed, 9 insertions(+), 4 deletions(-)\n>\n> diff --git a/src/ipa/rkisp1/algorithms/awb.cpp b/src/ipa/rkisp1/algorithms/awb.cpp\n> index 26d7b8138f17..4bb4f5b88375 100644\n> --- a/src/ipa/rkisp1/algorithms/awb.cpp\n> +++ b/src/ipa/rkisp1/algorithms/awb.cpp\n> @@ -210,13 +210,18 @@ void Awb::process(IPAContext &context,\n> \t\t});\n> \n> \t\t/*\n> -\t\t * Convert from YCbCr to RGB.\n> -\t\t * The hardware uses the following formulas:\n> -\t\t * Y = 16 + 0.2500 R + 0.5000 G + 0.1094 B\n> +\t\t * Convert from YCbCr to RGB. The hardware uses the following\n> +\t\t * formulas:\n> +\t\t *\n> +\t\t * Y = 16 + 0.2500 R + 0.5000 G + 0.1094 B\n> \t\t * Cb = 128 - 0.1406 R - 0.2969 G + 0.4375 B\n> \t\t * Cr = 128 + 0.4375 R - 0.3750 G - 0.0625 B\n> \t\t *\n> -\t\t * The inverse matrix is thus:\n> +\t\t * This seems to be based on limited range BT.601 with Q1.6\n> +\t\t * precision.\n> +\t\t *\n> +\t\t * The inverse matrix is:\n> +\t\t *\n> \t\t * [[1,1636, -0,0623, 1,6008]\n> \t\t * [1,1636, -0,4045, -0,7949]\n> \t\t * [1,1636, 1,9912, -0,0250]]","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 13D9CC326B\n\tfor ;\n\tTue, 19 Nov 2024 10:40:45 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 963AE65EF0;\n\tTue, 19 Nov 2024 11:40:44 +0100 (CET)","from us-smtp-delivery-124.mimecast.com\n\t(us-smtp-delivery-124.mimecast.com [170.10.133.124])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 6888D65EE9\n\tfor ;\n\tTue, 19 Nov 2024 11:40:42 +0100 (CET)","from mail-ej1-f71.google.com (mail-ej1-f71.google.com\n\t[209.85.218.71]) by relay.mimecast.com with ESMTP with STARTTLS\n\t(version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id\n\tus-mta-166-AG2CH_jNOFm8CmzCxkLc0g-1; 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\n\tTue, 19 Nov 2024 02:40:37 -0800 (PST)","by 2002:a17:907:f79b:b0:aa4:ce42:fa7f with SMTP id\n\ta640c23a62f3a-aa4ce4304fcmr140569266b.7.1732012837299; \n\tTue, 19 Nov 2024 02:40:37 -0800 (PST)"],"X-Google-Smtp-Source":"AGHT+IHMxnJRl5c/CcsbU36vvJF1bflPbD6w6GU0UlQm6O6ZHvNMXjEExDyahGiDkFm6T1zzHCn4/w==","From":"Milan Zamazal ","To":"Laurent Pinchart ","Cc":"libcamera-devel@lists.libcamera.org","Subject":"Re: [PATCH v3 17/17] ipa: rkisp1: awb: Expand comment","In-Reply-To":"<20241118221618.13953-18-laurent.pinchart@ideasonboard.com>\n\t(Laurent Pinchart's message of \"Tue, 19 Nov 2024 00:16:18 +0200\")","References":"<20241118221618.13953-1-laurent.pinchart@ideasonboard.com>\n\t<20241118221618.13953-18-laurent.pinchart@ideasonboard.com>","Date":"Tue, 19 Nov 2024 11:40:35 +0100","Message-ID":"<87zflvfqvw.fsf@redhat.com>","User-Agent":"Gnus/5.13 (Gnus v5.13)","MIME-Version":"1.0","X-Mimecast-Spam-Score":"0","X-Mimecast-MFC-PROC-ID":"uTL3t_rL7PpM12VDQkL-WTc9NCRuHUHS_sM-Cjuc7Jo_1732012838","X-Mimecast-Originator":"redhat.com","Content-Type":"text/plain","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\" "}}]