Experimental Physics and
Industrial Control System

<[email protected]> · Wed, 1 Sep 2010 13:14:57 +0100

Hi,

Tom Cobb is away this week so I am chipping in on his behalf. The latest
version (which we are using, but have not yet released) uses the
nullhttpd server instead of the mjpeg-streamer http server and ffmpeg as
the compression engine. This allows it to be portable across Windows and
Linux and so can be used with all those cameras that only come with
Windows drivers. I think Tom also said that ffmpeg is more efficient and
versatile than jpeglib

Tom has recently done some benchmarks to help us spec video servers for
GigE cameras. It is not simple because the system can bottleneck in a
number of ways. There are obvious CPU and network (both incoming from
the cameras and outgoing to the clients) bottlenecks, but there also
appears to be a bottleneck when a lot of cameras are used, despite
network and CPU utilisation being apparently low. However, if you have
multiple people viewing a stream you win a lot with compression since
you only do the compression once, but win in the reduction of outgoing
traffic.

As a guide, on an Intel X5260 processor (Dell 2950) with 3 1024x768 Mono
cameras @ 30fps uses 30% of 1 core for acquisition and another 35-40%
for compression. The compressed stream is about 10% of the uncompressed
stream. However, despite the data from the three cameras only being
70Mbytes/sec, only one core being utilised so another core is idle, and
it being a fully switched network, if you add another camera then frames
start being dropped. So, as they say, your mileage may vary.

Cheers,

Nick Rees

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Mark Rivers
Sent: 31 August 2010 18:20
To: [email protected]
Cc: EPICS Techtalk
Subject: RE: areaDetector video (Was: network video)

Which areaDetector driver are you using, i.e. for what detector/camera?

I am talking about an areaDetector plugin written at Diamond which takes
uncompressed detector images, compresses them to mjpeg and serves them
in an http server so they can be displayed in Web browsers and other
applicatations.

http://controls.diamond.ac.uk/downloads/support/mjpgServer/index.html

This is from the documentation:

"This module is an Linux only mjpg server plug-in for another EPICS
support module/framework: areaDetector by Mark Rivers, University of
Chicago. It makes extensive use of the http server from the
mjpeg-streamer project, and uses a combination of this and jpeglib to
allow clients such as Firefox or MPlayer to view a compressed stream of
the data produced by an areaDetector driver."

Mark

-----Original Message-----
From: [email protected]
[mailto:[email protected]] 
Sent: Tuesday, August 31, 2010 12:10 PM
To: Mark Rivers
Cc: John Dobbins; EPICS Techtalk
Subject: areaDetector video (Was: network video)

Mark, 

Are you talking about the Motion JPEG for CCD?
I use the areaDetector driver and am using NFS to access the data.
Is the MJPEG plugin your are talking about used to access/display the
CCD images?

As a side note, I am currently looking at a 10Hz rate acquisition CCD.
That could be a nice feature to have....

Is anyone familiar with adxv?
http://www.scripps.edu/~arvai/adxv.html
Is anything more recent? 
The GUI is so ... 1990s!

Thanks,

--
E

On 14:53 Mon 30 Aug     , Mark Rivers wrote:
> John,
> 
> For the areaDetector package Tom Cobb at Diamond has written an MJPEG
> plugin that compresses the video to reduce the network bandwidth.
This
> will work with any areaDetector camera.
> 
> Mark
> 
-- 
Emmanuel

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System