Can we write ImageSeries in external_mode if the timestamps are well specified

[h-mayorquin]

Right now when external mode is chosen we have the starting frames as a requirement:

neuroconv/src/neuroconv/datainterfaces/behavior/video/videodatainterface.py

Lines 327 to 329 in 2da9f6b

	if external_mode:
	image_series_kwargs = videos_metadata[0]
	if self._number_of_files > 1 and starting_frames is None:

That is, for ImageSeries of multiple videos in external mode, we add the requirements of starting_frames. Is this necessary? I can't see any of this specified on pynwb:

https://pynwb.readthedocs.io/en/stable/pynwb.image.html

What is the logic here?
My feeling is that if the timestamps are well specfiied then we should be able to write the ImageSeries.

[CodyCBakerPhD]

The timestamps don't tell you the number of frames in each external video file

As far as PyNWB, no I don't think it's a strict requirement, or even technically a best practice just yet, but I think it's a 'highly recommended' strategy

The closest mention we get is in the code https://github.com/NeurodataWithoutBorders/pynwb/blob/a6fa9170f2ad6942d74eaf44c22cedf0b80f0fcd/src/pynwb/image.py#L82-L90

[h-mayorquin]

No, but if you have the timestamps, this should not matter right? As in, you know at what time in your experiment each of the frames in the TimeSeries occured.

[CodyCBakerPhD]

It's not just about the timing of the frames, it's valuable context about how the shape of the total ImageSeries is distributed across the external files

Example: one very short video and one very long one - nearly contiguous but slightly irregular timestamps - timestamps alone do not tell you exactly which frames of the timestamp vector correspond to which video file

[h-mayorquin]

OK, thanks, I undestand that is very important information.

The logic as I understand it now is that: an external file with wihout information would be very incomplete, so we don't let you, even if you could.

[CodyCBakerPhD]

The logic as I understand it now is that: an external file with wihout information would be very incomplete, so we don't let you, even if you could.

As I currently understand it

NWB-schema: this is an optional field
PyNWB: we check the field and auto-fill if only a single file - possible plans to warn to specify if using external mode but you can technically skip if you want
NeuroConv/GUIDE: not currently required, but it can be easily grabbed from the external files and set automatically for convenience

[h-mayorquin]

Right, I guess we are moving towards there in #464