[Elphel-support] Setting exposure time via PHP

[David Haberthür]

Dear Andrey.

>From your scripts I've seen that I have to wait at least three frames,
this is what I'm doing [1] in the file.

I was thinking that I can load a certain frame persistently with
CamIP/FrameNumber/bimg, but this doesn't seem to be the case, since
inputting the frame number into the URL with 'elphel_get_frame()'
results in a 1x1 gif, thus a non-existing image.

I have seen that the images in the table of 9 images that you mention
("Last acquired images" when setting parameters) have completely
different numbers in their URL (CamIP/*Number*/bimg), for frame numbers
increasing by one, the *Number* increases by
	- approximately 404000 for TRIG_PERIOD=48000000
	- approximately 440000 for TRIG_PERIOD=19200000, EXPOS=10000
	- approximately 450000 for TRIG_PERIOD=10000000, EXPOS=1000
	- approximately 460000 for TRIG_PERIOD=96000000, EXPOS=50000
thus seemingly unrelated to trigger period and exposure time.

Is there no way to construct an URL to load a certain image/frame number
*after* having waited three frames after having set new parameters?

David

[1]: http://git.io/9oWgUg#L77

On 03/26/2013 03:02 AM, support-list wrote:
> Oleg, David,
> 
> There is latency in the sensor, so when camera sends i2c command to
> sensor it takes 3 frames before you'll get the frame with new exposure.
> If you do not specify which frame do you want to apply changes to,
> default is 3 frames ahead, and driver "knows" when to send parameters
> change to the sensor so 3 frames after now you'll get the new exposure.
> Different parameters have different latencies, and free
> running/triggered mode also has them different. There is some debug
> feature embedded in parsedit.php - you may change several parameters
> with different delays and open a table of 9 images - each will have
> caption with effective paramer values and frame numbers (some frame that
> are output "bad" by the sensor may be dropped - it happens when you
> change frame format).
> 
> Andrey
> 
> ---- On Mon, 25 Mar 2013 18:44:56 -0700 *Oleg
> <support-list at support.elphel.com>* wrote ----
> 
>     Hi David,
> 
>         When I load the script on the camera [5], I see that the
>         parameters are
>         changed, as PHP tells me, but the image I load after changing the
>         exposure time is the same as before (or at least the brightness
>         doesn't
>         change), or isn't loaded at all.
> 
> 
>     The problem is that PHP prints the output page once the script is
>     done... and the browser starts downloading these images after the
>     page is printed - so it always gets the latest images.
>      
>     What you can do is:
>     1. use "flush();" in PHP - I remember it worked a while ago it but
>     couldn't make it work for the past hour.
>     2. if you get "flush()" working  you might bump into browser
>     buffering images - so, for "src"-tag it's better to make up
>     different addresses, e.g.:
> 
>         <img
>         src='http://".$_SERVER['HTTP_HOST'].":8081/img?".microtime()."'
>         width='200' />
> 
> 
>     3. Use AJAX calls with JS to load images and run scripts.
> 
>     Best regards,
>     Oleg Dzhimiev
>     Electronics Engineer
>     phone: +1 801 783 5555 x124
>     Elphel, Inc.
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> 
> 
>