[PATCH v2 0/3] gstreamer: Generate controls from control_ids_*.yaml files

[Laurent Pinchart]

On Thu, Oct 03, 2024 at 12:18:54PM +0200, Jaslo Ziska wrote:
> Laurent Pinchart <laurent.pinchart at ideasonboard.com> writes:
> > On Wed, Oct 02, 2024 at 07:27:34PM +0200, Jaslo Ziska wrote:
> >> Laurent Pinchart <laurent.pinchart at ideasonboard.com> writes:
> >> > On Wed, Oct 02, 2024 at 12:04:08PM +0200, Jaslo Ziska wrote:
> >> >> Nicolas Dufresne <nicolas at ndufresne.ca> writes:
> >> >> > Le lundi 30 septembre 2024 à 11:11 +0200, Jaslo Ziska a écrit :
> >> >> >> Laurent Pinchart <laurent.pinchart at ideasonboard.com> writes:
> >> >> >> > Hi Jaslo,
> >> >> >> > 
> >> >> >> > I think this series is close to being ready, and I would be very happy
> >> >> >> > to merge this much awaited feature. Do you plan to send a v3 ?
> >> >> >> 
> >> >> >> Yes, I very much plan on continuing to work on this. I was a 
> >> >> >> pretty busy the past month but I should have more time later in 
> >> >> >> October.
> >> >> >> 
> >> >> >> Unfortunately, I don't think that the series is quite ready. 
> >> >> >> Nicolas had requested some bigger changes in v1 which still need 
> >> >> >> to be discussed and implemented and I also want to add the 
> >> >> >> readable/writeable and minimum/maximum properties to the yaml 
> >> >> >> files (although this could also be done separately after merging).
> >> >> >
> >> >> > My proposal is to program a subset to be exposed as properties, the one that are
> >> >> > obviously usable and that the documentation make sense. I think you did a great
> >> >> > job on the generator and adding features later to support controls that have
> >> >> > more complex semantic is better then trying to support them all in one go today.
> >> >> 
> >> >> Sounds good. Where would you suggest the list of controls to be 
> >> >> exposed should be? Maybe just a plain list in the Python generator 
> >> >> file?
> >> >
> >> > The other option is to store the information in the yaml files. I don't
> >> > have a very strong opinion, the yaml files have the advantage that all
> >> > the data related to controls will be in a single place, but the
> >> > generator script has the advantage of keeping all gstreamer-related data
> >> > close to the gstreamer element. That may be useful when it will be time
> >> > to move libcamerasrc from the libcamera repository to the gstreamer
> >> > repository (if we ever do so). On the other hand, tha yaml files are not
> >> > installed, so there would still be issues.
> >> 
> >> Putting it inside the yaml would be an option, but I don't know 
> >> whether having GStreamer specific stuff there is so good. But I 
> >> think this will likely change anyway.
> >> 
> >> > Complete brainstorming mode, I'm wondering if at some point in the
> >> > future it would make sense to handle the gstreamer controls in a more
> >> > dynamic fashion by querying libcamera at runtime instead of using code
> >> > generation. This doesn't invalidate the approach you've taken here, I
> >> > think code generation is good for the time being.
> >> 
> >> If you mean that the GStreamer properties should get added later 
> >> at runtime then this is unfortunately not possible. This is 
> >> because the GStreamer controls are GObject properties and those 
> >> need to be installed when the GObject object class is initialized. 
> >> And because this happens before the GStreamer element is 
> >> constructed (and therefore also before libcamera gets involved) it 
> >> is not possible to know which properties are present and with 
> >> which ranges.
> >
> > You can get the list of all the controls that libcamera supports from
> > libcamera::controls::controls. It's a global ControlIdMap variable, a
> > map from control numerical ids to ControlId instances. The ControlId
> > class gives you the control numerical id, its name, type, number of
> > elements if it's an array, and enumerators. We're adding the control
> > namespace as well, and could add additional information if needed. We
> > don't need to go this way though.
> 
> Ah yes, I think that would work too, I never thought about it that 
> way. This still would not help with the actually available 
> controls for the camera unfortunately.
> 
> I don't know which way would be the proper or better way to do it, 
> both ways have their pros and cons.
> 
> Using the yaml files and the code generator has more flexibility 
> but adds the complexity of the extra code. And using the 
> libcamera::controls::controls variable would probably simplify the 
> code but makes the GStreamer element dependent on the information 
> which are exposed by the variable.

One thing missing in ControlId (beside the namespace that we will add
soon) that you would need for libcamerasrc is documentation. I'm not too
keen on adding that to ControlId, it's lots of text, which would
probably then need localization.

> I'm open to both possibilities. Does anyone have opinions on this?

I think it's more important at this point to have a working version than
a perfect version, so I'm fine continuing with the current approach.

> >> The one thing that Nicolas suggested is adding a special property 
> >> to the GStreamer element which can then return the available 
> >> properties and their ranges at runtime. That would be the 
> >> GstStructure which I was asking about.
> >> 
> >> >> > If the selection is all rw, the marking of that can wait. 
> >> >> > Min/max would be my
> >> >> > preference to have, but as we are breaking the API anyway 
> >> >> > still, we can also do
> >> >> > small break in the gstreamer element later too (as long as 
> >> >> > its well reported in
> >> >> > the release notes).
> >> >> 
> >> >> You also suggested a GStreamer property that returns a 
> >> >> GstStructure which lists all the actually present controls for the 
> >> >> camera and their actual limits. Do you still want this implemented 
> >> >> and if so how do you imagine this structure to be laid out?
> >> >> 
> >> >> >> > On Tue, Aug 13, 2024 at 02:25:04PM +0200, Jaslo Ziska wrote:
> >> >> >> > > Hi everyone,
> >> >> >> > > 
> >> >> >> > > this is the second version of the patch set to implement gstreamer controls
> >> >> >> > > from the yaml files.
> >> >> >> > > This now depends on "[PATCH 00/10] libcamera: Improve code generation for
> >> >> >> > > controls" for the code generation.
> >> >> >> > > 
> >> >> >> > > The following things changed:
> >> >> >> > > 
> >> >> >> > > The (old) third commit fixing a typo has been removed as it is already merged.
> >> >> >> > > 
> >> >> >> > > The first commit is new: it removes the auto-focus-mode property from the
> >> >> >> > > device provider where it has been added on accident.
> >> >> >> > > 
> >> >> >> > > The commit message has been updated in the second commit.
> >> >> >> > > 
> >> >> >> > > The third commit, which adds the code that generates the gstreamer controls,
> >> >> >> > > now makes use of jinja2 and the new controls.py file. As a consequence the
> >> >> >> > > whole code generation has been redone.
> >> >> >> > > 
> >> >> >> > > There are also some new features:
> >> >> >> > > 
> >> >> >> > > It is now possible to read the metadata returned by requests from the gstreamer
> >> >> >> > > properties. This is done using a new function readMetadata() which reads the
> >> >> >> > > ControlList in requestCompleted().
> >> >> >> > > 
> >> >> >> > > Before a control is set it is now checked whether this control is actually
> >> >> >> > > supported by the camera. This is done by checking the cameras ControlInfoMap.
> >> >> >> > > 
> >> >> >> > > The Rectangle type is now supported.
> >> >> >> > > 
> >> >> >> > > Some checks were added to make sure the arrays passed to the element have the
> >> >> >> > > correct length.
> >> >> >> > > 
> >> >> >> > > Best regards,
> >> >> >> > > 
> >> >> >> > > Jaslo
> >> >> >> > > 
> >> >> >> > > Jaslo Ziska (3):
> >> >> >> > >   gstreamer: Remove auto-focus-mode property from device provider
> >> >> >> > >   gstreamer: Remove auto-focus-mode property from libcamerasrc
> >> >> >> > >   gstreamer: Generate controls from control_ids_*.yaml files
> >> >> >> > > 
> >> >> >> > >  src/gstreamer/gstlibcamera-controls.cpp.in | 296 +++++++++++++++++++++
> >> >> >> > >  src/gstreamer/gstlibcamera-controls.h      |  43 +++
> >> >> >> > >  src/gstreamer/gstlibcameraprovider.cpp     |  15 --
> >> >> >> > >  src/gstreamer/gstlibcamerasrc.cpp          |  50 ++--
> >> >> >> > >  src/gstreamer/meson.build                  |  10 +
> >> >> >> > >  utils/codegen/controls.py                  |   8 +
> >> >> >> > >  utils/codegen/gen-gst-controls.py          | 151 +++++++++++
> >> >> >> > >  utils/codegen/meson.build                  |   1 +
> >> >> >> > >  8 files changed, 528 insertions(+), 46 deletions(-)
> >> >> >> > >  create mode 100644 src/gstreamer/gstlibcamera-controls.cpp.in
> >> >> >> > >  create mode 100644 src/gstreamer/gstlibcamera-controls.h
> >> >> >> > >  create mode 100755 utils/codegen/gen-gst-controls.py

-- 
Regards,

Laurent Pinchart