[v5,20/24] ipa: camera_sensor_helper: Introduce exposure margin

28686 diff mbox series

From: Jacopo Mondi <jacopo.mondi@ideasonboard.com>

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 <jacopo.mondi@ideasonboard.com>
Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
---
 src/ipa/libipa/camera_sensor_helper.cpp | 68 +++++++++++++++++++++++++
 src/ipa/libipa/camera_sensor_helper.h   |  2 +
 2 files changed, 70 insertions(+)

Hi Barnabás

On Thu, 29 Oct 2026 at 12:59, Barnabás Pőcze
<barnabas.pocze@ideasonboard.com> wrote:
>
> From: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
>
> 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 <jacopo.mondi@ideasonboard.com>
> Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> ---
>  src/ipa/libipa/camera_sensor_helper.cpp | 68 +++++++++++++++++++++++++
>  src/ipa/libipa/camera_sensor_helper.h   |  2 +
>  2 files changed, 70 insertions(+)
>
> diff --git a/src/ipa/libipa/camera_sensor_helper.cpp b/src/ipa/libipa/camera_sensor_helper.cpp
> index 359040ec74..aee768a981 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 known
> + */
> +
>  /**
>   * \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
> @@ -387,6 +403,7 @@ public:
>         {
>                 /* Power-on default value: 168 at 12bits. */
>                 blackLevel_ = 2688;
> +               exposureMargin_ = 4;
>         }
>
>         uint32_t gainCode(double gain) const override
> @@ -473,6 +490,11 @@ 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);
> @@ -503,6 +525,7 @@ public:
>                 /* From datasheet: 64 at 10bits. */
>                 blackLevel_ = 4096;
>                 gain_ = AnalogueGainLinear{ 100, 0, 0, 1024 };
> +               exposureMargin_ = 4;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("gc05a2", CameraSensorHelperGc05a2)
> @@ -515,6 +538,7 @@ public:
>                 /* From datasheet: 64 at 10bits. */
>                 blackLevel_ = 4096;
>                 gain_ = AnalogueGainLinear{ 100, 0, 0, 1024 };
> +               exposureMargin_ = 16;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("gc08a3", CameraSensorHelperGc08a3)
> @@ -525,6 +549,7 @@ public:
>         CameraSensorHelperHm1246()
>         {
>                 gain_ = AnalogueGainLinear{ 1, 16, 0, 16 };
> +               exposureMargin_ = 2;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("hm1246", CameraSensorHelperHm1246)
> @@ -537,6 +562,7 @@ public:
>                 /* From datasheet: 64 at 10bits. */
>                 blackLevel_ = 4096;
>                 gain_ = AnalogueGainLinear{ 0, 512, -1, 512 };
> +               exposureMargin_ = 10;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("imx214", CameraSensorHelperImx214)
> @@ -549,6 +575,7 @@ public:
>                 /* From datasheet: 64 at 10bits. */
>                 blackLevel_ = 4096;
>                 gain_ = AnalogueGainLinear{ 0, 256, -1, 256 };
> +               exposureMargin_ = 4;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("imx219", CameraSensorHelperImx219)
> @@ -561,6 +588,7 @@ public:
>                 /* From datasheet: 0x40 at 10bits. */
>                 blackLevel_ = 4096;
>                 gain_ = AnalogueGainLinear{ 0, 512, -1, 512 };
> +               exposureMargin_ = 10;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("imx258", CameraSensorHelperImx258)
> @@ -573,6 +601,7 @@ public:
>                 /* From datasheet: 0x32 at 10bits. */
>                 blackLevel_ = 3200;
>                 gain_ = AnalogueGainLinear{ 0, 2048, -1, 2048 };
> +               exposureMargin_ = 4;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("imx283", CameraSensorHelperImx283)
> @@ -585,6 +614,7 @@ public:
>                 /* From datasheet: 0xf0 at 12bits. */
>                 blackLevel_ = 3840;
>                 gain_ = AnalogueGainExp{ 1.0, expGainDb(0.3) };
> +               exposureMargin_ = 2;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("imx290", CameraSensorHelperImx290)
> @@ -595,6 +625,11 @@ 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)
> @@ -612,6 +647,7 @@ public:
>                 /* From datasheet: 0x32 at 10bits. */
>                 blackLevel_ = 3200;
>                 gain_ = AnalogueGainExp{ 1.0, expGainDb(0.3) };
> +               exposureMargin_ = 10;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("imx335", CameraSensorHelperImx335)
> @@ -624,6 +660,7 @@ public:
>                 /* From datasheet: 64 at 10bits. */
>                 blackLevel_ = 4096;
>                 gain_ = AnalogueGainLinear{ 0, 1024, -1, 1024 };
> +               exposureMargin_ = 4;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("imx355", CameraSensorHelperImx355)
> @@ -634,6 +671,7 @@ public:
>         CameraSensorHelperImx415()
>         {
>                 gain_ = AnalogueGainExp{ 1.0, expGainDb(0.3) };
> +               exposureMargin_ = 8;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("imx415", CameraSensorHelperImx415)
> @@ -652,6 +690,7 @@ public:
>                 blackLevel_ = 4096;
>                 /* gain = 1024/(1024 - code); code = [0, 800]; max gain = x4.57 */
>                 gain_ = AnalogueGainLinear{ 0, 1024, -1, 1024 };
> +               exposureMargin_ = 18;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("imx471", CameraSensorHelperImx471)
> @@ -662,6 +701,7 @@ public:
>         CameraSensorHelperImx477()
>         {
>                 gain_ = AnalogueGainLinear{ 0, 1024, -1, 1024 };
> +               exposureMargin_ = 22;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("imx477", CameraSensorHelperImx477)
> @@ -674,6 +714,7 @@ public:
>                 /* From datasheet: 0xc8 at 12bits. */
>                 blackLevel_ = 3200;
>                 gain_ = AnalogueGainExp{ 1.0, expGainDb(0.3) };
> +               exposureMargin_ = 2;

This should be the same as imx678 at 4.
However David P has seen issues in HCG mode (not supported in
mainline) which may require 6. That is still being investigated.

>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("imx662", CameraSensorHelperImx662)
> @@ -686,6 +727,7 @@ public:
>                 /* From datasheet: 0x32 at 10bits. */
>                 blackLevel_ = 3200;
>                 gain_ = AnalogueGainExp{ 1.0, expGainDb(0.3) };
> +               exposureMargin_ = 8; /* \todo kernel driver: 8, rpi: 4 */

The kernel driver is wrong. Fixed in
https://lore.kernel.org/linux-media/20261022-media-starvis2-v6-7-374343f55fd3@raspberrypi.com/
(v7 coming soon)

  Dave

>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("imx678", CameraSensorHelperImx678)
> @@ -697,6 +739,7 @@ public:
>         {
>                 blackLevel_ = 4096;
>                 gain_ = AnalogueGainLinear{ 0, 1024, -1, 1024 };
> +               exposureMargin_ = 48;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("imx708", CameraSensorHelperImx708)
> @@ -709,6 +752,7 @@ public:
>                 /* From dark frame measurement: 0x40 at 10bits. */
>                 blackLevel_ = 4096;
>                 gain_ = AnalogueGainLinear{ 1, 0, 0, 256 };
> +               exposureMargin_ = 8;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("ov01a10", CameraSensorHelperOv01a10)
> @@ -721,6 +765,7 @@ public:
>                 /* From Linux kernel driver: 0x40 at 10bits. */
>                 blackLevel_ = 4096;
>                 gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> +               exposureMargin_ = 6;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("ov08d10", CameraSensorHelperOv08d10)
> @@ -732,6 +777,7 @@ public:
>         {
>                 blackLevel_ = 4096;
>                 gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> +               exposureMargin_ = 8;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("ov08x40", CameraSensorHelperOv08x40)
> @@ -744,6 +790,7 @@ public:
>                 blackLevel_ = 3600;
>                 /* gain is fixed to 1x, this is just a place holder. */
>                 gain_ = AnalogueGainLinear{ 0, 2048, -1, 2048 };
> +               exposureMargin_ = 6;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("mira220", CameraSensorHelperMira220)
> @@ -758,6 +805,7 @@ public:
>                  * This has been validated with some empirical testing only.
>                  */
>                 gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> +               exposureMargin_ = 4;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("ov2685", CameraSensorHelperOv2685)
> @@ -770,6 +818,7 @@ public:
>                 /* From Linux kernel driver: 0x40 at 10bits. */
>                 blackLevel_ = 4096;
>                 gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> +               exposureMargin_ = 8;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("ov2740", CameraSensorHelperOv2740)
> @@ -782,6 +831,7 @@ public:
>                 /* From datasheet: 0x40 at 12bits. */
>                 blackLevel_ = 1024;
>                 gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> +               exposureMargin_ = 4;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("ov4689", CameraSensorHelperOv4689)
> @@ -794,6 +844,14 @@ 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)
> @@ -804,6 +862,7 @@ public:
>         CameraSensorHelperOv5647()
>         {
>                 gain_ = AnalogueGainLinear{ 1, 0, 0, 16 };
> +               exposureMargin_ = 4;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("ov5647", CameraSensorHelperOv5647)
> @@ -814,6 +873,7 @@ public:
>         CameraSensorHelperOv5670()
>         {
>                 gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> +               exposureMargin_ = 8;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("ov5670", CameraSensorHelperOv5670)
> @@ -826,6 +886,7 @@ public:
>                 /* From Linux kernel driver: 0x40 at 10bits. */
>                 blackLevel_ = 4096;
>                 gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> +               exposureMargin_ = 4;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("ov5675", CameraSensorHelperOv5675)
> @@ -837,6 +898,7 @@ public:
>         {
>                 blackLevel_ = 1024;
>                 gain_ = AnalogueGainLinear{ 1, 0, 0, 16 };
> +               exposureMargin_ = 8;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("ov5693", CameraSensorHelperOv5693)
> @@ -847,6 +909,7 @@ public:
>         CameraSensorHelperOv64a40()
>         {
>                 gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> +               exposureMargin_ = 32;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("ov64a40", CameraSensorHelperOv64a40)
> @@ -863,6 +926,7 @@ 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)
> @@ -873,6 +937,7 @@ public:
>         CameraSensorHelperOv8865()
>         {
>                 gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> +               exposureMargin_ = 8;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("ov8865", CameraSensorHelperOv8865)
> @@ -883,6 +948,7 @@ public:
>         CameraSensorHelperOv13858()
>         {
>                 gain_ = AnalogueGainLinear{ 1, 0, 0, 128 };
> +               exposureMargin_ = 8;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("ov13858", CameraSensorHelperOv13858)
> @@ -895,6 +961,7 @@ public:
>                 /* From datasheet: 0x40 at 10bits. */
>                 blackLevel_ = 4096;
>                 gain_ = AnalogueGainLinear{ 0, 32, -1, 32 };
> +               exposureMargin_ = 64;
>         }
>  };
>  REGISTER_CAMERA_SENSOR_HELPER("vd55g1", CameraSensorHelperVd55g1)
> @@ -907,6 +974,7 @@ 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<int16_t> blackLevel() const { return blackLevel_; }
> +       std::optional<uint32_t> 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<int16_t> blackLevel_;
>         std::variant<std::monostate, AnalogueGainLinear, AnalogueGainExp> gain_;
> +       std::optional<uint32_t> exposureMargin_;
>
>  private:
>         LIBCAMERA_DISABLE_COPY_AND_MOVE(CameraSensorHelper)
> --
> 2.56.0
>

2026. 10. 29. 15:01 keltezéssel, Dave Stevenson írta:
> Hi Barnabás
> 
> On Thu, 29 Oct 2026 at 12:59, Barnabás Pőcze
> <barnabas.pocze@ideasonboard.com> wrote:
>>
>> From: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
>>
>> 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 <jacopo.mondi@ideasonboard.com>
>> Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
>> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
>> ---
>>   src/ipa/libipa/camera_sensor_helper.cpp | 68 +++++++++++++++++++++++++
>>   src/ipa/libipa/camera_sensor_helper.h   |  2 +
>>   2 files changed, 70 insertions(+)
>>
>> diff --git a/src/ipa/libipa/camera_sensor_helper.cpp b/src/ipa/libipa/camera_sensor_helper.cpp
>> index 359040ec74..aee768a981 100644
>> --- a/src/ipa/libipa/camera_sensor_helper.cpp
>> +++ b/src/ipa/libipa/camera_sensor_helper.cpp
> [...]
>> @@ -674,6 +714,7 @@ public:
>>                  /* From datasheet: 0xc8 at 12bits. */
>>                  blackLevel_ = 3200;
>>                  gain_ = AnalogueGainExp{ 1.0, expGainDb(0.3) };
>> +               exposureMargin_ = 2;
> 
> This should be the same as imx678 at 4.
> However David P has seen issues in HCG mode (not supported in
> mainline) which may require 6. That is still being investigated.

Thanks, fixed. It would be nice to eventually merge these details into one database.


> 
>>          }
>>   };
>>   REGISTER_CAMERA_SENSOR_HELPER("imx662", CameraSensorHelperImx662)
>> @@ -686,6 +727,7 @@ public:
>>                  /* From datasheet: 0x32 at 10bits. */
>>                  blackLevel_ = 3200;
>>                  gain_ = AnalogueGainExp{ 1.0, expGainDb(0.3) };
>> +               exposureMargin_ = 8; /* \todo kernel driver: 8, rpi: 4 */
> 
> The kernel driver is wrong. Fixed in
> https://lore.kernel.org/linux-media/20261022-media-starvis2-v6-7-374343f55fd3@raspberrypi.com/
> (v7 coming soon)

Thanks again, using 4.


> 
>    Dave
> 
>>          }
>>   };
>>   REGISTER_CAMERA_SENSOR_HELPER("imx678", CameraSensorHelperImx678)> [...]