[Elphel-support] linescan mode

[Michael Aschauer]

Dear Andrey,

I had a brief chance to testdrive it - also should do that more, - but 
and seems to work!

I have two main question / issues:

* there are two error lines at the end of each frame. Is there a 
technical reason for this? Would it easily be possible to get rid of 
them before compression?

* variable framerate? I run the linescan with variable framerate (which 
worked well with elphel 333). But I have some troubles to figure out how 
to do that correctly. That's not just with photofinish mode, but also in 
normal mode.

I currently do the linescan on the host computer, streaming a ROI of 
2592x48 - depending on quality settings this is possible up to 424 
frames per second (and strangely the height of 48 seem to deliver best 
performance. it significally drops if below that 48px)

setting the framerate via FPSFLAG and FPSLIM1000 works as expected with 
auto-exposure turned on. but if exposure is set manual (which is what I 
use), it seems to me exposure time is actually determining the framerate 
(and not the FPSLIM1000 setting). I work around that with internal 
triggering the camera but that has it's on glitches (for instance 
performance strangely drops if exposure time is below 3ms)

and none of both options seem to work well in linescan mode and manual 
exposure....

so far,
m,-




Am 2010-04-28 04:58, schrieb Andrey Filippov:
>
> I will need to test the code some more (current version is really
> experimental and have some glitches), but it seems that the lines can
> mode is back in 8.0.6.6 firmware. It supports up to 16K of lines in each
> composite frame (frames are supposed to perfectly match - no gaps
> between them). With full line of 2592 pixels the regular 5MPix sensor of
> the 353 camera can handle about 2500 line pairs (they go in pairs as the
> sensor is color) per second.
>
> The same mode should be useful to get the top fps for small images
> avoiding the CPU overhead related to the file headers and just
> processing the frame interrupts. It is possible now to combine multiple
> small images (not just 2-line rectangles) to the total height of up to
> 16K lines in a single composite image.
>
> Here are some samples (original and some - rotated/cropped):
>
> http://community.elphel.com/pictures/linescan/
>
> It is fun that cars going in the opposite directions on the freeway are
> going the same direction on the image. You may also notice something
> like huge chromatic aberration - it is caused by the car crossing one of
> the line in a color pair before the other.
>
> Many images are acquired at reduced rate (they have "582lps" in the
> name) so the cars look more proportional, at the full 2425 lp/s they
> look too long.
>
> Andrey