[Elphel-support] Questions about the sensor in Elphel353

[Andrey Filippov]

Diana,

Yes - all of them. I would recommend using just jp4 (color mode 5) in the
camera drop-down menu. You may also use JP46 (color mode 4) - it is the
easiest to open with the programs as if it was a regular JPEG (i.e. in the
browser). There will be "distortions", but image as a whole will look like
original. JP4 has an advantage that you can run full resolution 5MPix images
at full sensor rate, while JP46 will limit frame rate to 10.6 fps.

It is causes by dummy color components in JP46 (for compatibility with color
JPEG), and FPGA compressor code requires 2 cycles per pixel (clock is
160MHz). In JP4 mode each source pixel produces 1 compressed sample, in JP46
(as in color YCbCr 4:2:0) - 1.5Pix (for each 16x16 macroblock it compresses
4 of Y 8x8 blocks, one Cb 8x8 block and one Cr 8x8 block).

So compressor pixel rate (referenced to sensor pixels) will be
160MHz/2=80MPix/sec for JP4 and 160MHz/3~=53MPix/sec for JPEG and JP46.
For 2592*1936 images that results in 15.94fps for JP4 and 10.63fps for
JPEG/JP46. 15.96fps is above the sensor capabilities, so in that case the
frame rate is limited by the sensor (if not network/hdd, of course, but that
depends on the nature of the image, compression quality and coring
settings).

Both JP4 and JP46 are supported by ImageJ plugin (
http://elphel.git.sourceforge.net/git/gitweb.cgi?p=elphel/ImageJ-Elphel;a=blob;f=JP46_Reader_camera.java),
plugin also reads custom MakerNote Exif data that contains gamma
conversion settings in the camera as well as analog gains, so the result
opened image (as 32-bit floating point) has the pixel values proportional to
raw sensor ones. Plugin can read saved files or get images directly from the
camera.  And it as other Elphel software is released under GNU GPLv3
license, so you can use the available source code to write your own program
(i.e. in different programming language).

Andrey




On Wed, Oct 26, 2011 at 9:40 AM, Diana Carrigan
<DianaEJohnson at maxim-ic.com>wrote:

> Hello,****
>
> ** **
>
> Do all of the JP4 modes listed in the below article (under Different JP4
> Modes in 8.x Software) bypass the Demosaic in the FPGA. If not, which do and
> which don’t.****
>
> ** **
>
> Best Regards,****
>
> ** **
>
> Diana Carrigan****
>
> ** **
>
> *From:* Alexandre Poltorak [mailto:polto at alsenet.com]
> *Sent:* Tuesday, September 06, 2011 12:55 PM
> *To:* Diana Carrigan
> *Subject:* Re: [Elphel-support] Questions about the sensor in Elphel353***
> *
>
> ** **
>
> Hi,****
>
> ** **
>
> Please take a look here : http://wiki.elphel.com/index.php?title=JP4****
>
> ** **
>
> JP4 is Elphel's RAW format. Disk Recorder can record even long videos in
> JP4. ****
>
> ** **
>
> Conversion must be done on a computer in post-processing.****
>
> ** **
>
> Best regards,****
>
> Alexandre****
> ------------------------------
>
> *De: *"Diana Carrigan" <DianaEJohnson at maxim-ic.com>
> *À: *support-list at support.elphel.com
> *Envoyé: *Mardi 6 Septembre 2011 20:49:13
> *Objet: *[Elphel-support] Questions about the sensor in Elphel353
>
>
> ****
>
> Hello,****
>
>  ****
>
> We have a couple of questions I’m sure you guys can answer.****
>
>  ****
>
> 1)      What is the sensor data format defaulted to? (RGB? YUV?)****
>
> 2)      Does the sensor do an RGB to YUV conversion?****
>
> 3)      Can the Disk Recorder (or some other program) be used to create a
> data file of the video stream of the RAW RGB data (perhaps 5 seconds worth
> of video stream)?****
>
> Thanks for your help..****
>
>  ****
>
> Diana Carrigan****
>
>
> _______________________________________________
> Support-list mailing list
> Support-list at support.elphel.com
> http://support.elphel.com/mailman/listinfo/support-list_support.elphel.com
> ****
>
> ** **
>
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>
>
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