[Elphel-support] Questions about JP4

[Andrey Filippov]

On Wed, Nov 30, 2011 at 4:20 AM, Florent Thiery
<florent.thiery at ubicast.eu>wrote:

> Funny, when reading Movie2DNG's src/jp4.cpp:
>
>   // EXIF
>   readMakerNote();
>
>   // JP4 deblocking
>   // from
> http://code.google.com/p/gst-plugins-elphel/source/browse/trunk/jp462bayer/src/gstjp462bayer.c
>
> Is the JP4 to Bayer the same as JP46 to Bayer ?
>


Florent, JP4 and JP46 are handled very similarly. The important part is
handled the in the same way - un-applying gamma conversion according to
MakerNote data (the analog gains are also un-applied according to
MakerNote, but that is less critical). And I believe that after that step
and before any other processing (de-mosaic, aberration correction, ...) the
data should be kept with more than 8 bits per pixel. Theoretically it is
possible to pass gamma conversion data to the DNG (as was already done),
but in that case there are more possibilities for something getting wrong
with later conversion. So I would prefer to use linear 16+ bit intermediate
(after the JP4/JP46 specific processing) Bayer data.

Andrey
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