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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: Daniel Scally <dan.scally@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
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The terms "shutter" and "shutter speed" are used through libcamera to
mean "exposure time". This is confusing, both due to "speed" being used
as "time" while it should be the inverse (i.e. a maximum speed should
correspond to the minimum time), and due to "shutter speed" and
"exposure time" being used in different places with the same meaning.
To improve clarity of the code base and the documentation, use "exposure
time" consistently to replace "shutter speed".
This rename highlighted another vocabulary issue in libcamera. The
ExposureModeHelper::splitExposure() function used to document that it
splits "exposure time into shutter time and gain". It has been reworded
to "split exposure into exposure time and gain". That is not entirely
satisfactory, as "exposure" has a defined meaning in photography (see
https://en.wikipedia.org/wiki/Exposure_(photography)) that is not
expressed as a duration. This issue if left to be addressed separately.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
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Previous iterations of the ExposureModeHelper class had a
setShutterGainLimits() function, which got renamed to setLimits(). The
documentation still uses the old name. Fix it.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
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The gcc used in my current buildroot (Version 12.3) errors out with
-Wmaybe-uninitialized. Fix that.
Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
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Source files in libcamera start by a comment block header, which
includes the file name and a one-line description of the file contents.
While the latter is useful to get a quick overview of the file contents
at a glance, the former is mostly a source of inconvenience. The name in
the comments can easily get out of sync with the file name when files
are renamed, and copy & paste during development have often lead to
incorrect names being used to start with.
Readers of the source code are expected to know which file they're
looking it. Drop the file name from the header comment block.
The change was generated with the following script:
----------------------------------------
dirs="include/libcamera src test utils"
declare -rA patterns=(
['c']=' \* '
['cpp']=' \* '
['h']=' \* '
['py']='# '
['sh']='# '
)
for ext in ${!patterns[@]} ; do
files=$(for dir in $dirs ; do find $dir -name "*.${ext}" ; done)
pattern=${patterns[${ext}]}
for file in $files ; do
name=$(basename ${file})
sed -i "s/^\(${pattern}\)${name} - /\1/" "$file"
done
done
----------------------------------------
This misses several files that are out of sync with the comment block
header. Those will be addressed separately and manually.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
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Add a helper for managing exposure modes and splitting exposure times
into shutter and gain values.
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
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