From patchwork Thu Aug 27 10:41:06 2026 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: 28117 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 26F7DC3341 for ; Thu, 27 Aug 2026 10:41:24 +0000 (UTC) Received: from lancelot.ideasonboard.com (localhost [IPv6:::1]) by lancelot.ideasonboard.com (Postfix) with ESMTP id 182E86847E; Thu, 27 Aug 2026 12:41:22 +0200 (CEST) Authentication-Results: lancelot.ideasonboard.com; dkim=pass (1024-bit key; unprotected) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="hx+x2DrG"; 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 60AD268454 for ; Thu, 27 Aug 2026 12:41:12 +0200 (CEST) Received: from pb-laptop.local (185.221.143.32.nat.pool.zt.hu [185.221.143.32]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id C5C42C1; Thu, 27 Aug 2026 12:39:45 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1787827185; bh=TFLQmJlSkdJXE+KUF8qYAwZ5JmiR+wTlpKL7C5BTruM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hx+x2DrGFpGZvTz0C7Ojycycm7+xpCRtlnkmR1iyVcOsji01mEYCAbgEhHytpB4YM MczIizWkLYUJieIVp9a5sYoIgww8mPfIjRrn97q8CVq8SY3OKpPUsiGacXuerSgsTh MlPnpPJQXiPFjSUJgwBPCazXe4bpu/JZFpyZ496Y= From: =?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= To: libcamera-devel@lists.libcamera.org Cc: Jacopo Mondi Subject: [RFC PATCH v1 6/8] ipa: camera_sensor_helper: Introduce exposure margin Date: Thu, 27 Aug 2026 12:41:06 +0200 Message-ID: <20260827104108.1432632-7-barnabas.pocze@ideasonboard.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260827104108.1432632-1-barnabas.pocze@ideasonboard.com> References: <20260827104108.1432632-1-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 There is a margin between the maximum achievable shutter time and the frame length. The value is sensor-dependent and should be used to adjust the maximum achievable exposure time whenever the frame length changes. Introduce in the CameraSensorHelper the notion of exposureMargin_ as the minimum difference in number of lines between the current frame length and the maximum exposure time. This feature is already implemented in the RPi CamHelper class hierarchy with the name of frameIntegrationDiff. Populate the CameraSensorHelper instances with an exposureMargin_. The value of the exposure margin comes from the mainline driver version of each sensor, and it has been compared with the frameIntegrationDiff_ value in the rpi camera helpers. Signed-off-by: Jacopo Mondi Signed-off-by: Barnabás Pőcze Reviewed-by: Stefan Klug --- src/ipa/libipa/camera_sensor_helper.cpp | 59 +++++++++++++++++++++++++ src/ipa/libipa/camera_sensor_helper.h | 2 + 2 files changed, 61 insertions(+) diff --git a/src/ipa/libipa/camera_sensor_helper.cpp b/src/ipa/libipa/camera_sensor_helper.cpp index 1a90343c00..3da69bf17b 100644 --- a/src/ipa/libipa/camera_sensor_helper.cpp +++ b/src/ipa/libipa/camera_sensor_helper.cpp @@ -76,6 +76,16 @@ namespace ipa { * \return The black level of the sensor, or std::nullopt if not known */ +/** + * \fn CameraSensorHelper::exposureMargin() + * \brief Fetch the exposure margin of the sensor + * + * This function returns the exposure margin of the sensor, in lines, which + * is the minimum difference between the integration time and frame length. + * + * \return The exposure margin of the sensor, or std::nullopt if not know + */ + /** * \brief Compute gain code from the analogue gain absolute value * \param[in] gain The real gain to pass @@ -229,6 +239,12 @@ double CameraSensorHelper::quantizeGain(double _gain, double *quantizationGain) * sensor specific. Use this variable to store the values at init time. */ +/** + * \var CameraSensorHelper::exposureMargin_ + * \brief The smallest margin between the integration time and the frame length + * in lines + */ + /** * \class CameraSensorHelperFactoryBase * \brief Base class for camera sensor helper factories @@ -385,6 +401,7 @@ public: { /* Power-on default value: 168 at 12bits. */ blackLevel_ = 2688; + exposureMargin_ = 4; } uint32_t gainCode(double gain) const override @@ -474,6 +491,11 @@ REGISTER_CAMERA_SENSOR_HELPER("ar0144", CameraSensorHelperAr0144) class CameraSensorHelperAr0521 : public CameraSensorHelper { public: + CameraSensorHelperAr0521() + { + exposureMargin_ = 4; + } + uint32_t gainCode(double gain) const override { gain = std::clamp(gain, 1.0, 15.5); @@ -504,6 +526,7 @@ public: /* From datasheet: 64 at 10bits. */ blackLevel_ = 4096; gain_ = AnalogueGainLinear{ 100, 0, 0, 1024 }; + exposureMargin_ = 4; } }; REGISTER_CAMERA_SENSOR_HELPER("gc05a2", CameraSensorHelperGc05a2) @@ -516,6 +539,7 @@ public: /* From datasheet: 64 at 10bits. */ blackLevel_ = 4096; gain_ = AnalogueGainLinear{ 100, 0, 0, 1024 }; + exposureMargin_ = 16; } }; REGISTER_CAMERA_SENSOR_HELPER("gc08a3", CameraSensorHelperGc08a3) @@ -526,6 +550,7 @@ public: CameraSensorHelperHm1246() { gain_ = AnalogueGainLinear{ 1, 16, 0, 16 }; + exposureMargin_ = 2; } }; REGISTER_CAMERA_SENSOR_HELPER("hm1246", CameraSensorHelperHm1246) @@ -538,6 +563,7 @@ public: /* From datasheet: 64 at 10bits. */ blackLevel_ = 4096; gain_ = AnalogueGainLinear{ 0, 512, -1, 512 }; + exposureMargin_ = 10; } }; REGISTER_CAMERA_SENSOR_HELPER("imx214", CameraSensorHelperImx214) @@ -550,6 +576,7 @@ public: /* From datasheet: 64 at 10bits. */ blackLevel_ = 4096; gain_ = AnalogueGainLinear{ 0, 256, -1, 256 }; + exposureMargin_ = 4; } }; REGISTER_CAMERA_SENSOR_HELPER("imx219", CameraSensorHelperImx219) @@ -562,6 +589,7 @@ public: /* From datasheet: 0x40 at 10bits. */ blackLevel_ = 4096; gain_ = AnalogueGainLinear{ 0, 512, -1, 512 }; + exposureMargin_ = 10; } }; REGISTER_CAMERA_SENSOR_HELPER("imx258", CameraSensorHelperImx258) @@ -574,6 +602,7 @@ public: /* From datasheet: 0x32 at 10bits. */ blackLevel_ = 3200; gain_ = AnalogueGainLinear{ 0, 2048, -1, 2048 }; + exposureMargin_ = 4; } }; REGISTER_CAMERA_SENSOR_HELPER("imx283", CameraSensorHelperImx283) @@ -586,6 +615,7 @@ public: /* From datasheet: 0xf0 at 12bits. */ blackLevel_ = 3840; gain_ = AnalogueGainExp{ 1.0, expGainDb(0.3) }; + exposureMargin_ = 2; } }; REGISTER_CAMERA_SENSOR_HELPER("imx290", CameraSensorHelperImx290) @@ -596,6 +626,11 @@ public: CameraSensorHelperImx296() { gain_ = AnalogueGainExp{ 1.0, expGainDb(0.1) }; + /* + * The driver doesn't apply any margin. Use the value + * in RPi's CamHelper. + */ + exposureMargin_ = 4; } }; REGISTER_CAMERA_SENSOR_HELPER("imx296", CameraSensorHelperImx296) @@ -613,6 +648,7 @@ public: /* From datasheet: 0x32 at 10bits. */ blackLevel_ = 3200; gain_ = AnalogueGainExp{ 1.0, expGainDb(0.3) }; + exposureMargin_ = 9; } }; REGISTER_CAMERA_SENSOR_HELPER("imx335", CameraSensorHelperImx335) @@ -635,6 +671,7 @@ public: CameraSensorHelperImx415() { gain_ = AnalogueGainExp{ 1.0, expGainDb(0.3) }; + exposureMargin_ = 8; } }; REGISTER_CAMERA_SENSOR_HELPER("imx415", CameraSensorHelperImx415) @@ -663,6 +700,7 @@ public: CameraSensorHelperImx477() { gain_ = AnalogueGainLinear{ 0, 1024, -1, 1024 }; + exposureMargin_ = 22; } }; REGISTER_CAMERA_SENSOR_HELPER("imx477", CameraSensorHelperImx477) @@ -762,6 +800,7 @@ public: * This has been validated with some empirical testing only. */ gain_ = AnalogueGainLinear{ 1, 0, 0, 128 }; + exposureMargin_ = 4; } }; REGISTER_CAMERA_SENSOR_HELPER("ov2685", CameraSensorHelperOv2685) @@ -774,6 +813,7 @@ public: /* From Linux kernel driver: 0x40 at 10bits. */ blackLevel_ = 4096; gain_ = AnalogueGainLinear{ 1, 0, 0, 128 }; + exposureMargin_ = 8; } }; REGISTER_CAMERA_SENSOR_HELPER("ov2740", CameraSensorHelperOv2740) @@ -786,6 +826,7 @@ public: /* From datasheet: 0x40 at 12bits. */ blackLevel_ = 1024; gain_ = AnalogueGainLinear{ 1, 0, 0, 128 }; + exposureMargin_ = 4; } }; REGISTER_CAMERA_SENSOR_HELPER("ov4689", CameraSensorHelperOv4689) @@ -798,6 +839,14 @@ public: /* From datasheet: 0x10 at 10bits. */ blackLevel_ = 1024; gain_ = AnalogueGainLinear{ 1, 0, 0, 16 }; + /* + * Very convoluted in the driver that however applies a margin + * of 4 lines when setting vts. + * + * cap_vts = cap_shutter + 4; + * ret = ov5640_set_vts(sensor, cap_vts); + */ + exposureMargin_ = 4; } }; REGISTER_CAMERA_SENSOR_HELPER("ov5640", CameraSensorHelperOv5640) @@ -808,6 +857,7 @@ public: CameraSensorHelperOv5647() { gain_ = AnalogueGainLinear{ 1, 0, 0, 16 }; + exposureMargin_ = 4; } }; REGISTER_CAMERA_SENSOR_HELPER("ov5647", CameraSensorHelperOv5647) @@ -818,6 +868,7 @@ public: CameraSensorHelperOv5670() { gain_ = AnalogueGainLinear{ 1, 0, 0, 128 }; + exposureMargin_ = 8; } }; REGISTER_CAMERA_SENSOR_HELPER("ov5670", CameraSensorHelperOv5670) @@ -830,6 +881,7 @@ public: /* From Linux kernel driver: 0x40 at 10bits. */ blackLevel_ = 4096; gain_ = AnalogueGainLinear{ 1, 0, 0, 128 }; + exposureMargin_ = 4; } }; REGISTER_CAMERA_SENSOR_HELPER("ov5675", CameraSensorHelperOv5675) @@ -841,6 +893,7 @@ public: { blackLevel_ = 1024; gain_ = AnalogueGainLinear{ 1, 0, 0, 16 }; + exposureMargin_ = 8; } }; REGISTER_CAMERA_SENSOR_HELPER("ov5693", CameraSensorHelperOv5693) @@ -851,6 +904,7 @@ public: CameraSensorHelperOv64a40() { gain_ = AnalogueGainLinear{ 1, 0, 0, 128 }; + exposureMargin_ = 32; } }; REGISTER_CAMERA_SENSOR_HELPER("ov64a40", CameraSensorHelperOv64a40) @@ -867,6 +921,7 @@ public: * See: https://patchwork.linuxtv.org/project/linux-media/patch/20221106171129.166892-2-nicholas@rothemail.net/#142267 */ gain_ = AnalogueGainLinear{ 1, 0, 0, 128 }; + exposureMargin_ = 4; } }; REGISTER_CAMERA_SENSOR_HELPER("ov8858", CameraSensorHelperOv8858) @@ -877,6 +932,7 @@ public: CameraSensorHelperOv8865() { gain_ = AnalogueGainLinear{ 1, 0, 0, 128 }; + exposureMargin_ = 8; } }; REGISTER_CAMERA_SENSOR_HELPER("ov8865", CameraSensorHelperOv8865) @@ -887,6 +943,7 @@ public: CameraSensorHelperOv13858() { gain_ = AnalogueGainLinear{ 1, 0, 0, 128 }; + exposureMargin_ = 8; } }; REGISTER_CAMERA_SENSOR_HELPER("ov13858", CameraSensorHelperOv13858) @@ -899,6 +956,7 @@ public: /* From datasheet: 0x40 at 10bits. */ blackLevel_ = 4096; gain_ = AnalogueGainLinear{ 0, 32, -1, 32 }; + exposureMargin_ = 64; } }; REGISTER_CAMERA_SENSOR_HELPER("vd55g1", CameraSensorHelperVd55g1) @@ -911,6 +969,7 @@ public: /* From datasheet: 0x40 at 10bits. */ blackLevel_ = 4096; gain_ = AnalogueGainLinear{ 0, 32, -1, 32 }; + exposureMargin_ = 75; } }; REGISTER_CAMERA_SENSOR_HELPER("vd56g3", CameraSensorHelperVd56g3) diff --git a/src/ipa/libipa/camera_sensor_helper.h b/src/ipa/libipa/camera_sensor_helper.h index bd3d0beec7..a9e55c832d 100644 --- a/src/ipa/libipa/camera_sensor_helper.h +++ b/src/ipa/libipa/camera_sensor_helper.h @@ -27,6 +27,7 @@ public: virtual ~CameraSensorHelper() = default; std::optional blackLevel() const { return blackLevel_; } + std::optional exposureMargin() const { return exposureMargin_; } virtual uint32_t gainCode(double gain) const; virtual double gain(uint32_t gainCode) const; double quantizeGain(double gain, double *quantizationGain) const; @@ -46,6 +47,7 @@ protected: std::optional blackLevel_; std::variant gain_; + std::optional exposureMargin_; private: LIBCAMERA_DISABLE_COPY_AND_MOVE(CameraSensorHelper)