[Elphel-support] Setting exposure time via PHP

[support-list]

David,

The large random-looking numbers in the URL are absolurte positions in the circular buffer (~19MB), so if acquisition is not stopped they soon become invalid when the fames are overwritten by the new ones. And yes, if the specified pointer does not match exactly the start of some frame - 1x1 gif is returned.  If you want to read some frame in the future, you may just wait for that frame with php function, then read latest with imgsrv (port 8081 - it has mini help if you open the document root of that server, more in http://wiki.elphel.com/index.php?title=Imgsrv ). With imgsrv you may read current pointers in the circular buffer, and navigate it with /prev /last, ...

BTW, instead of the cycle skipping single frame you may use either
 elphel_wait_frame (long frame) 
or
 elphel_skip_frames (long frames)  

it will have less CPU overhead - the thread will contuinue execution when enabled by the driver that processes frame sync interrupts.

Andrey


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