Experimental Physics and
Industrial Control System

Steven Hunt <[email protected]> · Wed, 16 Nov 2005 22:36:02 +0100

The original firewire support for Epics I wrote (a long time ago), used
periodic record scanning.  This has the nasty effect that you have to
scan at twice the frame rate to be sure you miss nothing.

The later software using a PMC board under Vx-Works at Diamond uses I/O
interrupt  - This is the right way to do it as changing the frame rate
of the camera is the only thing you have to do to change the rate of the
whole processing chain. When the camera delivers a new frame to the
firewire card it will call Epics to process it.

On another point, for many applications you will not have to transfer
the 'raw' image at a high rate, but you can transfer the parameters
(beam size and position for instance), and only send the image at a
lower rate.

Anyone using this type of application should look at the very nice live
video edm widget written by Steve Singleton at Diamond. 

Steve Hunt

On Wed, 2005-11-16 at 11:31 -0800, Emmanuel Mayssat wrote:
> I am actually doing something quite similar, but I am using a standard
> camera with a frame grabber.
> The issue I am facing is related to synchronization and data processing.
> 
> For example I calculate the x and y profiles of a electron beam.
> But while I can acquire image at 30Hz, epics can only process the
> information at a maximum rate of 10Hz.
> 
> Is there a work around?
> Is it possible to do real time video with epics?
> 
> n Wed, 2005-11-16 at 13:44 +0100, Aladwan Ahed wrote:
> > Hi Matjaz,
> > 
> > At the SLS we interfaced CCD cameras with Firewire bus to EPICS (3.14.7 on Linux RH7.3), you can find all the info and the source code under:
> > 
> > http://epics.web.psi.ch/software/firewire/
> > 
> > We think Firewire is a good choice as it supports isochronous data - delivering data at a guaranteed rate. This makes it ideal for devices that need to transfer high priority data in real-time, such as video devices. It is also fast (400Mbit/sec) (53 frames/sec @ 1Byte and 1024*768 pixels and 80% usable bandwidth), actually, this is more than what the EPICS video server PC can process. The EPICS video server grabs the frames from the camera, process them, and then allow any CA enabled client application to access the processed data, this way we save our network bandwidth.
> > 
> > Cheers,
> > Ahed
> > 
> > ###########################################
> > # Ahed Aladwan                            
> > # SLS Controls / Paul Scherrer Institute  
> > # WSLA/208, 5232 Villigen PSI Switzerland 
> > # Tel:+41 56 310 4594                     
> > # Fax:+41 56 310 4413                     
> > # www.psi.ch                                                             
> > # http://people.web.psi.ch/adwan/                   
> > ###########################################
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System