[libcamera-devel] [PATCH v4 24/32] ipa: rkisp1: Document the active state and frame context
Laurent Pinchart
laurent.pinchart at ideasonboard.com
Thu Sep 22 22:35:48 CEST 2022
Hi Kieran,
On Wed, Sep 21, 2022 at 12:14:11AM +0100, Kieran Bingham wrote:
> Quoting Laurent Pinchart via libcamera-devel (2022-09-08 02:41:52)
> > Now that data used by algorithms has been partitioned between the active
> > state and frame context, we have a better view of the role of each of
> > those structures. Document them appropriately.
> >
> > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > ---
> > src/ipa/rkisp1/ipa_context.cpp | 55 ++++++++++++++++++++++++++++------
> > 1 file changed, 46 insertions(+), 9 deletions(-)
> >
> > diff --git a/src/ipa/rkisp1/ipa_context.cpp b/src/ipa/rkisp1/ipa_context.cpp
> > index b2628ef73d49..335cb32c538d 100644
> > --- a/src/ipa/rkisp1/ipa_context.cpp
> > +++ b/src/ipa/rkisp1/ipa_context.cpp
> > @@ -88,16 +88,28 @@ namespace libcamera::ipa::rkisp1 {
> > * \struct IPAActiveState
> > * \brief Active state for algorithms
> > *
> > - * The active state stores algorithm-specific data that needs to be shared
> > - * between multiple algorithms and the IPA module. It is accessible through the
> > - * IPAContext structure.
> > + * The active state contains all algorithm-specific data that need to be
>
> /need/needs/
>
> > + * maintained by algorithms across frames. Unlike the session configuration,
> > + * the active state is mutable and constantly updated by algorithms. The active
> > + * state is accessible through the IPAContext structure.
> > *
> > - * \todo Split the data contained in this structure between the active state
> > - * and the frame contexts.
> > + * The active state stores two distinct categories of information:
> > *
> > - * Each of the fields in the active state belongs to either a specific
> > - * algorithm, or to the top-level IPA module. A field may be read by any
> > - * algorithm, but should only be written by its owner.
> > + * - The consolidated value of all algorithm controls. Requests passed to
> > + * the queueRequest() function store values for controls that the
> > + * application wants to modify for that particular frame, and the
> > + * queueRequest() function updates the active state with those values.
> > + * The active state thus contains a consolidated view of the value of all
> > + * controls handled by the algorithm.
> > + *
> > + * - The value of parameters computed by the algorithm when running in auto
> > + * mode. Algorithms running in auto mode compute new parameters every
> > + * time statistics buffers are received (either synchronously, or
> > + * possibly in a background thread). The latest computed value of those
> > + * parameters is stored in the active state in the process() function.
> > + *
> > + * Each of the members in the active state belongs to a specific algorithm. A
> > + * member may be read by any algorithm, but shall only be written by its owner.
> > */
> >
> > /**
> > @@ -185,7 +197,32 @@ namespace libcamera::ipa::rkisp1 {
> > * \struct RkISP1FrameContext
> > * \brief Per-frame context for algorithms
> > *
> > - * \todo Populate the frame context for all algorithms
> > + * The frame context stores two distinct categories of information:
> > + *
> > + * - The value of the controls to be applied to the frame. These values are
> > + * typically set in the queueRequest() function, from the consolidated
> > + * control values stored in the active state. The frame context thus stores
> > + * values for all controls related to the algorithm, not limited to the
> > + * controls specified in the corresponding request, but consolidated from all
> > + * requests that have been queued so far.
> > + *
> > + * For controls that can be set manually or computed by an algorithm
> > + * (depending on the algorithm operation mode), such as for instance the
> > + * colour gains for the AWB algorithm, the control value will be stored in
> > + * the frame context in the queueRequest() function only when operating in
> > + * manual mode. When operating in auto mode, the values are computed by the
> > + * algorithm in process(), stored in the active state, and copied to the
> > + * frame context in prepare(), just before being stored in the ISP parameters
> > + * buffer.
> > + *
> > + * The queueRequest() function can also store ancillary data in the frame
> > + * context, such as flags to indicate if (and what) control values have
> > + * changed compared to the previous request.
> > + *
> > + * - Status information computed by the algorithm for a frame. For instance,
> > + * the colour temperature estimated by the AWB algorithm from ISP statistics
> > + * calculated on a frame is stored in the frame context for that frame in
> > + * the process() function.
>
> That all sounds fine. I wonder if some of the examples might need
> tweaking later, as I think for instance the colour temperature for a
> frame might go directlty into the metadata, as mentioned earlier. The
I agree. I'll probably rewrite this section to mention metadata instead
of colour temperature then.
> FrameContext is really only storing information about a frame that is
> required at multiple processing steps/calls. And the ColourTemperature
> is likely not needed (for a specific frame) after it's calculated,
> except to put it into the metadata for that frame.
>
>
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
>
> > */
> >
> > /**
--
Regards,
Laurent Pinchart
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