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When zones are used for the grey world algorithm, they are only
considered if their average green value is at least 32/255 to exclude
zones that are too dark and don't provide relevant colour information
(on the opposite side of the spectrum, saturated regions are excluded by
the ImgU statistics engine).
The algorithm requires a minimal number of zones that meet this criteria
in order to run. Now that we correct the black level, the 32/255 minimal
value is a bit high and prevents the algorithm for running in low-light
conditions. Lower the value to 16/255 to fix it.
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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The AWB grey world algorithm tries to find a grey value and it can't do
it on over-exposed images. To exclude those, the saturation ratio is
used for each cell, and the cell is included only if this ratio is 0.
Now that we have changed the threshold, more cells may be considered as
partially saturated and excluded, preventing the algorithm from running
efficiently.
Change that behaviour, and consider 90% as a good enough ratio.
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
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We can have a saturation ratio per cell, giving the percentage of pixels
over a threshold within a cell where 100% is set to 0xff.
The parameter structure 'ipu3_uapi_awb_config_s' contains four fields to
set the threshold, one per channel.
The blue field is also used to configure the ImgU and make it calculate
the saturation ratio or not.
Set a green value saturated when it is more than 230 (90% of the maximum
value 255, coded as 8191). As this is the only channel used for AGC,
there is no need to apply it to the other ones.
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
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The Awb::generateZones() member function fills the zones vector passed
as an argument, which is actually a member variable. Use it directly in
the function.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
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The intel-ipu3.h public interface from the kernel does not define how to
parse the statistics for a cell. This had to be identified by a process
of reverse engineering, and later identifying the structures from [0]
leading to our custom definition of struct Ipu3AwbCell.
[0]
https://chromium.googlesource.com/chromiumos/platform/arc-camera/+/refs/heads/master/hal/intel/include/ia_imaging/awb_public.h
To improve the kernel interface, a proposal has been made to the
linux-kernel [1] to incorporate the memory layout for each cell into the
intel-ipu3 header directly.
[1]
https://lore.kernel.org/linux-media/20211005202019.253353-1-jeanmichel.hautbois@ideasonboard.com/
Update our local copy of the intel-ipu3.h to match the proposal and
change the AGC and AWB algorithms to reference that structure directly,
allowing us to remove the deprecated custom Ipu3AwbCell definition.
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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The statistics buffer 'ipu3_uapi_awb_raw_buffer' stores the ImgU
calculation results in a buffer aligned horizontally to a multiple of 4
cells. The AWB loop should take care of it to add the proper offset
between lines and avoid any staircase effect.
It is no longer required to pass the grid configuration context to the
private functions called from process() which simplifies the code flow.
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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The gains have a precision u3.13, range [0, 8[ which means that a gain
multiplier value of 1.0 is represented as a multiplication by 8192 in
the ImgU. Correct the gains as this was misunderstood in the first
place.
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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The algorithm uses the statistics of a cell only if there is not too
much saturated pixels in it. The grey world algorithm works fine when
there are a limited number of outliers.
Consider a valid zone to be at least 80% of unsaturated cells in it.
This value could very well be configurable, and make the algorithm more
or less tolerant.
While at it, implement it in a configure() call as it will not change
during execution, and cache the cellsPerZone values estimated with
std::round as we are using cmath.
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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The variables mix the terms cell, region and zone. It can confuse the
reader, and make the algorithm more difficult to follow. Rename the
local variables to be consistent with their definitions:
- Cells are defined in Pixels
- Zones are defined in Cells
There is no "region" as such, so replace it with the correct term.
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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The pixel component sums for the Accumulator are inconsistent with other
similar structures such as the IPAFrameContext::awb::gains. Group the
red, green, and blue sums together in a struct and store them as
uint64_t to reduce potential architectural differences.
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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The IspStatsRegion structure was introduced as an attempt to prepare for
a generic AWB algorithm structure. The structure name by itself is not
explicit and it is too optimistic to try and make a generic one for now.
Its role is to accumulate the pixels in a given zone. Rename it to
accumulator, and remove the uncounted field at the same time. It is
always possible to know how many pixels are not relevant for the
algorithm by calculating total-counted. The uncounted field was only
declared and not used. Amend the documentation accordingly.
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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The IPASessionConfiguration now has the grid configuration stored. Use
it it at prepare() and process() calls in AWB and pass it as a reference
to the private functions when needed.
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
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Now that the interface is properly used by the AWB class, move it into
ipa::ipu3::algorithms and let the loops do the calls.
Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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