[libcamera-devel] [PATCH v4] py: cam.py: Provide live graph of request metadata

[Kieran Bingham]

Quoting Tomi Valkeinen (2023-03-06 14:26:37)
> Hi,
> 
> On 02/02/2023 17:03, Daniel Oakley wrote:
> > Metadata is very useful when improving specific camera configurations.
> > Currently, there is an argument to display the metadata in text form,
> > however this can be hard to visualise and spot changes or patterns over
> > time. Therefore this proposed patch adds an argument to display this
> > metadata in graph form.
> > 
> > The metadata graph has 3 optional parameters:
> >   - refresh, number of times a second to update the graph
> >   - buffer, amount of historic/previous data to show
> >   - graphs, number of graphs to split the metadata between
> >   - autoscale, whether or not to autoscale the axis so all the data fits
> > 
> > Displaying the graph does have some performance penalty, however this
> > has been mostly mitigated through the refresh parameter. Despite this,
> > graphing might not the best of ideas when using the camera to record or
> > save data. This is mainly for debugging purposes.
> > 
> > Suggested-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> > Signed-off-by: Daniel Oakley <daniel.oakley at ideasonboard.com>
> > ---
> > This is the 4th version of my graph-metadata patch.
> > v3: hopefully addressing the issue of there being a lot of additional
> > code in the main cam.py which is optional. Most of the code has been
> > moved into a cam_metadata_graph.py file, which is imported at the start
> > of cam.py (as opposed to importing it twice throughout the code to make
> > the GraphDrawer and process the arguments). I have slightly tweaked the
> > error handling with the metadata-graph's arguments to catch a division
> > by zero error for refresh=0 and added a comment explanation for the
> > metadata-graph argument processor.
> > v4: I forgot to add the copywrite information to the new file, hopefully
> > I did it roughly correct.
> > There should, again, be no functional change between V1 and V2 and v3
> > 
> >   src/py/cam/cam.py                |  22 +++
> >   src/py/cam/cam_metadata_graph.py | 236 +++++++++++++++++++++++++++++++
> >   2 files changed, 258 insertions(+)
> >   create mode 100644 src/py/cam/cam_metadata_graph.py
> 
> What HW and OS did you use to test this?
> 
> I tried with RPi OS, and after installing lots of stuff and finally getting libcamera compiling on the device, I got:
> 
> Traceback (most recent call last):
>    File "/home/tomba/nfs/libcamera/./src/py/cam/cam.py", line 253, in event_handler
>      self.__request_handler(ctx, req)
>    File "/home/tomba/nfs/libcamera/./src/py/cam/cam.py", line 284, in __request_handler
>      ctx.graph_drawer.update_graph(ts, req.metadata)
>    File "/home/tomba/nfs/libcamera/src/py/cam/cam_metadata_graph.py", line 81, in update_graph
>      self.__animate()
>    File "/home/tomba/nfs/libcamera/src/py/cam/cam_metadata_graph.py", line 169, in __animate
>      self.blit_manager.update()
>    File "/home/tomba/nfs/libcamera/src/py/cam/cam_metadata_graph.py", line 206, in update
>      self.on_draw(None)
>    File "/home/tomba/nfs/libcamera/src/py/cam/cam_metadata_graph.py", line 189, in on_draw
>      self._draw_animated()
>    File "/home/tomba/nfs/libcamera/src/py/cam/cam_metadata_graph.py", line 200, in _draw_animated
>      fig.draw_artist(a)
>    File "/usr/lib/python3/dist-packages/matplotlib/figure.py", line 1879, in draw_artist
>      raise AttributeError("draw_artist can only be used after an "
> AttributeError: draw_artist can only be used after an initial draw which caches the renderer
> 
> I'm still trying to get pyqt and matplotlib working on my buildroot...
> 
> While I don't yet quite know how this behaves and looks like, I do wonder if this
> is something that would be better done with a separate script. We already have
> --save-frames option, we could add --save-metadata. And use matplotlib to show that
> data, possibly on a separate device (I'm thinking of showing it on my PC, as the dirs
> are shared via NFS).

But that doesn't work 'live'. I've tested this (or a previous version) -
and it allows me to get an instant and direct view of the repsonses in
the IPA algorithms as I adjust for lighting conditions etc.

--
Kieran


> 
>   Tomi
>