TraitError: The 'filename' trait of an ImageRecorder instance must be a unicode string

[chalgand]

Hello,

I would like to apply visual processing on stream of my camera but...

from ipywebrtc import CameraStream, ImageRecorder
camera = CameraStream(constraints=
                                      {'facing_mode': 'user',
                                       'audio': False,
                                       'video': { 'width': 640, 'height': 480 }
                                       })
camera
image_recorder = ImageRecorder(stream=camera)
image_recorder

I get an error by IPython on my jupyter lab :
TraitError: The 'filename' trait of an ImageRecorder instance must be a unicode string, but a value of traitlets.Undefined <class 'traitlets.utils.sentinel.Sentinel'> was specified.

Best,

[martinRenou]

Which version of ipywebrtc are you using? If not 0.4.3 would you mind trying to update ipywebrtc? I suppose this is fixed in the last release.

As a workaround, you can try this code:

from ipywebrtc import CameraStream, ImageRecorder
camera = CameraStream(constraints=
                                      {'facing_mode': 'user',
                                       'audio': False,
                                       'video': { 'width': 640, 'height': 480 }
                                       })
camera
image_recorder = ImageRecorder(stream=camera, filename='record')
image_recorder

[chalgand]

Hi Martin,

I have a conda environment up to date :
-ipywebrtc 0.4.3

• python 3.7.3
• jupyterlab 0.35.4

The full error message is :
`

TraitError Traceback (most recent call last)
in
----> 1 image_recorder = ImageRecorder(stream=camera)
2 image_recorder

C:\ProgramData\Anaconda3\envs\formation\lib\site-packages\ipywebrtc\webrtc.py in init(self, format, filename, recording, autosave, **kwargs)
352 def init(self, format='png', filename=Undefined, recording=False, autosave=False, **kwargs):
353 super(ImageRecorder, self).init(
--> 354 format=format, filename=filename, recording=recording, autosave=autosave, **kwargs)
355 if 'image' not in kwargs:
356 # Set up initial observer on child:

C:\ProgramData\Anaconda3\envs\formation\lib\site-packages\ipywidgets\widgets\widget.py in init(self, **kwargs)
409 """Public constructor"""
410 self._model_id = kwargs.pop('model_id', None)
--> 411 super(Widget, self).init(**kwargs)
412
413 Widget._call_widget_constructed(self)

C:\ProgramData\Anaconda3\envs\formation\lib\site-packages\traitlets\traitlets.py in init(self, *args, **kwargs)
995 for key, value in kwargs.items():
996 if self.has_trait(key):
--> 997 setattr(self, key, value)
998 else:
999 # passthrough args that don't set traits to super

C:\ProgramData\Anaconda3\envs\formation\lib\site-packages\traitlets\traitlets.py in set(self, obj, value)
583 raise TraitError('The "%s" trait is read-only.' % self.name)
584 else:
--> 585 self.set(obj, value)
586
587 def _validate(self, obj, value):

C:\ProgramData\Anaconda3\envs\formation\lib\site-packages\traitlets\traitlets.py in set(self, obj, value)
557
558 def set(self, obj, value):
--> 559 new_value = self._validate(obj, value)
560 try:
561 old_value = obj._trait_values[self.name]

C:\ProgramData\Anaconda3\envs\formation\lib\site-packages\traitlets\traitlets.py in _validate(self, obj, value)
589 return value
590 if hasattr(self, 'validate'):
--> 591 value = self.validate(obj, value)
592 if obj._cross_validation_lock is False:
593 value = self._cross_validate(obj, value)

C:\ProgramData\Anaconda3\envs\formation\lib\site-packages\traitlets\traitlets.py in validate(self, obj, value)
2052 msg = "Could not decode {!r} for unicode trait '{}' of {} instance."
2053 raise TraitError(msg.format(value, self.name, class_of(obj)))
-> 2054 self.error(obj, value)
2055
2056

C:\ProgramData\Anaconda3\envs\formation\lib\site-packages\traitlets\traitlets.py in error(self, obj, value)
623 e = "The '%s' trait must be %s, but a value of %r was specified."
624 % (self.name, self.info(), repr_type(value))
--> 625 raise TraitError(e)
626
627 def get_metadata(self, key, default=None):

TraitError: The 'filename' trait of an ImageRecorder instance must be a unicode string, but a value of traitlets.Undefined <class 'traitlets.utils.sentinel.Sentinel'> was specified.
`

Regards,

[martinRenou]

Weird, I would have thought it is fixed on the last release.

Did you try the workaround I gave you?

[chalgand]

Oh, i'm sorry.

Your code works fine ! Thank you

Best regards

[martinRenou]

If you don't mind I will keep this issue opened until we fix it properly.

Thanks a lot for reporting this issue!