get each field/ interlaced frames through v4l4j

[Max Schulze]

Hello,

I am struggling over how to get each (TOP|BOTTOM) Field separately through
v4l4j (at 50, resp. 60 fps). [V4L2_FMT_FLAG_INTERLACED is the hint] As I have
sorted out, the is the possibility to tell v4l2 to switch to Interlaced Mode,
but apparently v4l4j does not offer a choice, right?
Is there anything planned or did I miss something?

Kind regards

M Schulze

[Gilles Gigan]

Hi Max,
You are correct, there is no way to specify the field order settings
for capture in the current version of v4l4j, but I can add it for you
within the next couple of days if you are happy to do the testing.
I am not sure whether to allow users to specify the field order for
all types of frame grabbers, or only for raw frame grabbers. Could you
tell me a bit more about your use case ?
Thanks
Gilles

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[Max Schulze]

Hi Gilles,

I am coming back on this project again. I have a small exposure (1/100 000) PAL Camera and I want to analyze each Field separately, as it blurs when I take the complete (2xfield=frame) image. I already tried to set V4L2_FIELD_INTERLACED in v4l2-input.c (l 294) but apparently I still do miss anything as I didn't fully understand the java part yet.
Do you mind giving anothe hint?

Kind regards,
M Schulze


[Gilles Gigan]

Hi Max,

Ok, so basically, depending on your driver, you may or may not request individual fields by changing the V4L2_FIELD_* parameter in v4l2-input.c

I have seen drivers which happily give you a single field when you request it, and drivers which wont even let you start capture if you ask for anything other than V4L2_FIELD_ANY (which is why v4l4j uses this one).

What happens when you try other V4L2_FIELD values (like V4L2_FIELD_BOTTOM or V4L2_FIELD_INTERLACED) ? can you start capturing or do you get an exception ?

Gilles

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