[Elphel-support] Exposure priority

[Andrey Filippov]

Dimitrios,

I recommend you to play with autocampars.php (that calls parsedit.php) or
with parsedit.php directly (if you open it w/o parameters it will open a
page with some examples). It is important to understand, that there is no
such thing as "currtent settings" in the camera - the parameters are
applied with different latencies that match the in-camera pipeline
(sensor->FPGA->CPU), accounting fro different sensor latencies for
different parameters. parsedit.php lets you to specify - which frame to
apply parameters. Hardware (FPGA) supports an 8-frame deep queue for the
parameters, 5 of them can be used to write parameters ahead of the target
frame.

As for "gain priority" there is no such algorithm implemented - the
autoexposure daemon (apps/autoexposure) handles both WB and exposure, but
gains are only adjusted for WB.

Andrey


On Tue, Jan 3, 2012 at 4:20 PM, Dimitrios <dz at telemetry.gr> wrote:

> Hi Oleg.
> Thank you for the quick reply.
>
> > scene is not blurred. Different default gains for sunny/cloudy
> > conditions might work. What do you think?
>
> Yes, I do exactly this with gain presets and works fine. I might try to
> implement an algorithm for 'exposure priority', but it'll have to be
> external to the camera for now, and I guess the latency will not be very
> small. I see two versions of the 'exposure priority':
>
> 1. Lax: auto-adjust gain (within limits, e.g. max 8) and if at the upper
> limit, then adjust exposure.
> 2. Strict: auto-adjust gain and if at the  upper limit do nothing.
>
> This brings a few more questions:
>
> - Is the 'gain-priority' algorithm implemented in the FPGA? If not,
> could you please point me to the source file where I can find it?
>
> - Camvc parameters ae, aef and ael set auto-exposure, auto-exposure
> level and auto-exposure fraction, as I can tell by looking at the AJAX
> requests sent by the browser to the camera. What is the parameter/tag
> for the actual percentage of pixels below ael in the response XML? Would
> that be the <hist_out> family of values? I see the <hist_out_g> value
> very close to the one reported in camvc's screen.
>
> Regards
> Dimitrios
>
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