[Elphel-support] change camera parameters through Telnet

Thu Dec 13 17:42:39 PST 2012

Biel,

so it is not the Python script?

parsedit.php is a development tool - for quite a while it did not have GET mode, and by default it schedules the parameter modification to 3 frames in the future (you may use EXPOS=1000*0 to overwrite that, but the frame +0 will to be affected anyway - 2 frames will be lost in the sensor) - the longest delay it may take the sensor (different commands have different latency). Actually parsedit.php allows you to make multiple parameter changes at different frames and then open 9 last images with the parameter values below so you can troubleshoot latencies.
3 frames will take 12 ms, the rest may be the laptop opening and running wget.

Andrey

---- On Thu, 13 Dec 2012 17:10:06 -0800 Biel Bestué de Luna<7318.tk at gmail.com> wrote ---- 

ok,

about the wget:

I'm currently using a WAN router attached to the camera, I connect the camera to it via ethrnet, and I connect my laptop to the router via WiFi

then I setup the camera to triggered in order to have a fixed rate of 25 fps with the API I talked before

I open a real time stream with gstreamer at low latency in my laptop to see the real time reaction:

"gst-launch-0.10 rtspsrc location=rtsp://elphel:554 protocols=0x00000001 latency=40 ! rtpjpegdepay ! jpegdec ! queue ! xvimagesink"

then I open the terminal and write this:

"wget --delete-after 'http://elphel/parsedit.php?immediate&EXPOS=100&'"

(EXPOS at some strange value so I see the change easily)

I see the change 1 second after I touch intro

2012/12/14 support-list <support-list at support.elphel.com>
  Biel,

It will be quite a work to do a C program - as I said the easiest will be to adapt the php extension code (written in C). But agan - I do not think you'll get much of the performance gain (if any) compared to PHP - we use it ourselves and it is fast.

Andrey

---- On Thu, 13 Dec 2012 15:51:45 -0800 Biel Bestué de Luna<7318.tk at gmail.com> wrote ---- 

 Andrey
you talked before about the possibility to create a C coded program, how would someone interact with that program would that be a daemon like the php application seems to be working? if so would it be any better than php resource-wise?

if a C coded application could be added in order to cover this rapid control and data acces, could both applications (php application and C coded application) coexists using the same parameters? so if you change EXPOS via wget you see the change right away in the C coded program and vice versa...
 so both applications would cover diferent usages of the camera, one could cover the current usage, where you can do everythin in camera, and the other would cover a more service-like usage where the camera serves the purpose of recording/shooting device, and other functions remain in another computer not inside the camera. what do you think? 

2012/12/14 support-list <support-list at support.elphel.com>

> the idea was to unload that work from the camera, and leave all the important processing to the external computer,

 Yes, we do the same with Eyesis, there is a lot of processing, but PHP is still used in to control the camera

> like Flavio Soares does, he deactivates the php functions of the camera so it can record at a higher quality jpeg compression.

What does "deactivates the php functions of the camera" mean?

He does not use the camera GUI? Yes, that GUI is rather slow, but not slower that it was before the PHP was implemented in the camera (camvc is rather old - at least 6-7 years).

Using PHP in the camera is the fastest way to control it. Of course, if you will run Drupal there - it will be terribly slow, but just changing few parameters you really need - it will be faster than telnet. 

> what would be cool would be to have an abstraction layer that would cover that kind of usage of the camera, for rapid interaction with the camera.

Camera control functionality is implemented in PHP extension - http://wiki.elphel.com/index.php?title=PHP_in_Elphel_cameras . Any simple "API" like in many cameras would definitely limit the functionality, so we decided that user can make her own API, coding it in PHP. It can be universal, but big and likely slow. Or it can be tailored to particular application - and be really fast.

Andrey

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