Issues when testing 1.13 new features (The MMAL Tour in the doc)

Hello all and well done for the work on picamera.

This library will be very useful on a project I am working on, especially the new features 1.13 version is adding. I’d like to add some information drawn over a record, so I’m triing to make the examples of “The MMAL Tour” working. The first samples are working well, but when it arrives to what I want, I have some problems to make them work.

For example, I tested the 16.1.11 Python Components example which can be summarized by :

from picamera import mmal, mmalobj as mo
from picamera import array

camera = mo.MMALCamera()
preview = mo.MMALRenderer()

class Crosshair(array.PiArrayTransform):
  def transform(self, source, target):
    with source as sdata, target as tdata:
      tdata[...] = sdata
      tdata[240, :, :] = 0xff
      tdata[:, 320, :] = 0xff
    return False

transform = Crosshair()

camera.outputs[0].framesize = (640, 480)
camera.outputs[0].framerate = 30
camera.outputs[0].commit()

transform.connect(camera.outputs[0])
preview.connect(transform)
transform.connection.enable()
preview.connection.enable()
transform.enable()

and this code doesn’t do anything. What am I doing wrong ? What do I forget ? I tried to eliminate some commands in the previous chapters to keep only the ones that should be necessary for the example …

16.1.9 example didn’t work either, but it seemed to be more complicated that this one.

By the way, I have pointed out some misprint in the doc, where can I spot them ?

Thanks for all 😃

Jean-Rodolphe Letertre

[waveform80]

Apologies I haven’t got time to work on this at the moment (it’s going to be at least another month before I get free time for picamera again). For anyone wanting to play with older versions:

1. Learn about virtualenvs. There’s the virtualenv user guide or pipenv guide or probably plenty of others. Anyway, learn it, get comfortable with it.

2. Once you’re in a venv you can pip install any version of picamera at all; I never delete old versions from PyPI so everything back to 0.3 (the first version released on PyPI) is still available. Just do pip install picamera==1.12 (or whatever version you fancy).

3. You can also git clone this repository and hack on the code yourself within a venv (there’s development instructions in the documentation).

[waveform80]

Sadly I haven’t got much time to look into this, but I can confirm the issue and the proposed workaround by @JimKnowler. Unfortunately that doesn’t help much: read the commit message and you’ll see that reverting that commit just breaks #311 again. There’s obviously something about MMAL’s output buffer handling that I’m not understanding (and hence which goes wrong when the Python-side of the mmalobj components are used). Unfortunately, the pure Python components in mmalobj are of extremely niche interest compared to having capture_continuous work properly so until I/someone can come up with a “proper” fix things will have to stay as they are.

That said, if you’re playing around with mmalobj, I expect you’re more than capable of reverting a commit so I don’t feel too guilty 😉