| Message ID | 20250227195821.3172905-1-stefan.klug@ideasonboard.com |
|---|---|
| State | Accepted |
| Commit | eb550486c737305dd7e86187e9d76d95d35a9cfd |
| Headers | show |
| Series |
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| Related | show |
Hi Stefan On 27/02/2025 19:58, Stefan Klug wrote: > The ExposureModeHelper::splitExposures() runs through the configured > stages to find the best gain/exposure time pair. It first raises the > exposure time until it reaches the limit of the current stage. Then it > raises the gain until that also reaches the limit of the current stage. > After that it continues with the next stage until a match is found. > > Due to a slight mistake in the initial code, the second step doesn't > work as expected because the exposure time gets divided by the gain of > the current stage, effectively leading to a jump of the gain value from > the maximum gain of the last stage to the maximum gain of the current > stage instead of gradually increasing the gain value. > > Depending on the tuning file this leads to very visible oscillations and > jumps in the brightness. > > Fix by clamping the exposure time in the second step to the maximum > exposure time of the current stage. Great catch! > While at it, add two comments for easier understanding. Honestly those two make the whole thing so much clearer...and so does directly specifying stageExposureTime. Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com> > > Fixes: 34c9ab62827b ("ipa: libipa: Add ExposureModeHelper") > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com> > --- > src/ipa/libipa/exposure_mode_helper.cpp | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/src/ipa/libipa/exposure_mode_helper.cpp b/src/ipa/libipa/exposure_mode_helper.cpp > index f235316d3539..0c1e99e31a47 100644 > --- a/src/ipa/libipa/exposure_mode_helper.cpp > +++ b/src/ipa/libipa/exposure_mode_helper.cpp > @@ -182,6 +182,7 @@ ExposureModeHelper::splitExposure(utils::Duration exposure) const > * the stage limits are initialised. > */ > > + /* Clamp the gain to lastStageGain and regulate exposureTime. */ > if (stageExposureTime * lastStageGain >= exposure) { > exposureTime = clampExposureTime(exposure / clampGain(lastStageGain)); > gain = clampGain(exposure / exposureTime); > @@ -189,8 +190,9 @@ ExposureModeHelper::splitExposure(utils::Duration exposure) const > return { exposureTime, gain, exposure / (exposureTime * gain) }; > } > > + /* Clamp the exposureTime to stageExposureTime and regulate gain. */ > if (stageExposureTime * stageGain >= exposure) { > - exposureTime = clampExposureTime(exposure / clampGain(stageGain)); > + exposureTime = clampExposureTime(stageExposureTime); > gain = clampGain(exposure / exposureTime); > > return { exposureTime, gain, exposure / (exposureTime * gain) };
On Thu, Feb 27, 2025 at 08:58:10PM +0100, Stefan Klug wrote: > The ExposureModeHelper::splitExposures() runs through the configured > stages to find the best gain/exposure time pair. It first raises the > exposure time until it reaches the limit of the current stage. Then it > raises the gain until that also reaches the limit of the current stage. > After that it continues with the next stage until a match is found. > > Due to a slight mistake in the initial code, the second step doesn't > work as expected because the exposure time gets divided by the gain of > the current stage, effectively leading to a jump of the gain value from > the maximum gain of the last stage to the maximum gain of the current > stage instead of gradually increasing the gain value. > > Depending on the tuning file this leads to very visible oscillations and > jumps in the brightness. > > Fix by clamping the exposure time in the second step to the maximum > exposure time of the current stage. > > While at it, add two comments for easier understanding. > > Fixes: 34c9ab62827b ("ipa: libipa: Add ExposureModeHelper") > Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com> Reviewed-by: Paul Elder <paul.elder@ideasonboard.com> > --- > src/ipa/libipa/exposure_mode_helper.cpp | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/src/ipa/libipa/exposure_mode_helper.cpp b/src/ipa/libipa/exposure_mode_helper.cpp > index f235316d3539..0c1e99e31a47 100644 > --- a/src/ipa/libipa/exposure_mode_helper.cpp > +++ b/src/ipa/libipa/exposure_mode_helper.cpp > @@ -182,6 +182,7 @@ ExposureModeHelper::splitExposure(utils::Duration exposure) const > * the stage limits are initialised. > */ > > + /* Clamp the gain to lastStageGain and regulate exposureTime. */ > if (stageExposureTime * lastStageGain >= exposure) { > exposureTime = clampExposureTime(exposure / clampGain(lastStageGain)); > gain = clampGain(exposure / exposureTime); > @@ -189,8 +190,9 @@ ExposureModeHelper::splitExposure(utils::Duration exposure) const > return { exposureTime, gain, exposure / (exposureTime * gain) }; > } > > + /* Clamp the exposureTime to stageExposureTime and regulate gain. */ > if (stageExposureTime * stageGain >= exposure) { > - exposureTime = clampExposureTime(exposure / clampGain(stageGain)); > + exposureTime = clampExposureTime(stageExposureTime); > gain = clampGain(exposure / exposureTime); > > return { exposureTime, gain, exposure / (exposureTime * gain) }; > -- > 2.43.0 >
diff --git a/src/ipa/libipa/exposure_mode_helper.cpp b/src/ipa/libipa/exposure_mode_helper.cpp index f235316d3539..0c1e99e31a47 100644 --- a/src/ipa/libipa/exposure_mode_helper.cpp +++ b/src/ipa/libipa/exposure_mode_helper.cpp @@ -182,6 +182,7 @@ ExposureModeHelper::splitExposure(utils::Duration exposure) const * the stage limits are initialised. */ + /* Clamp the gain to lastStageGain and regulate exposureTime. */ if (stageExposureTime * lastStageGain >= exposure) { exposureTime = clampExposureTime(exposure / clampGain(lastStageGain)); gain = clampGain(exposure / exposureTime); @@ -189,8 +190,9 @@ ExposureModeHelper::splitExposure(utils::Duration exposure) const return { exposureTime, gain, exposure / (exposureTime * gain) }; } + /* Clamp the exposureTime to stageExposureTime and regulate gain. */ if (stageExposureTime * stageGain >= exposure) { - exposureTime = clampExposureTime(exposure / clampGain(stageGain)); + exposureTime = clampExposureTime(stageExposureTime); gain = clampGain(exposure / exposureTime); return { exposureTime, gain, exposure / (exposureTime * gain) };
The ExposureModeHelper::splitExposures() runs through the configured stages to find the best gain/exposure time pair. It first raises the exposure time until it reaches the limit of the current stage. Then it raises the gain until that also reaches the limit of the current stage. After that it continues with the next stage until a match is found. Due to a slight mistake in the initial code, the second step doesn't work as expected because the exposure time gets divided by the gain of the current stage, effectively leading to a jump of the gain value from the maximum gain of the last stage to the maximum gain of the current stage instead of gradually increasing the gain value. Depending on the tuning file this leads to very visible oscillations and jumps in the brightness. Fix by clamping the exposure time in the second step to the maximum exposure time of the current stage. While at it, add two comments for easier understanding. Fixes: 34c9ab62827b ("ipa: libipa: Add ExposureModeHelper") Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com> --- src/ipa/libipa/exposure_mode_helper.cpp | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)