Experimental Physics and
Industrial Control System

Dennis Armstrong <[email protected]> · Thu, 30 Aug 2007 08:29:16 +0200

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Emmanuel Mayssat wrote:
> All,
> 
> Following up on an old thread, I moved forward with an axis video
> server.
> I noted that Motion JPEG is the image format that is being used.
> To grab a snapshot we can use a program called axmjpeg that can extract
> snapshot from a video stream. This script works quite well. Initially I
> was afraid that disk write (of snapshot files) would significantly slow
> down the snapshot acquisition. But it doesn't appear to be the case (for
> 10Hz acquisition).
> (Note that the axmjpeg program can pipe its output as well (no disk
> write), or can directly be integrated in an epics driver (that's the
> beauty of having the source code)).
> 
> Then I closely looked at the JPEG format.
> JPEG is well suited for video IP (for compression reasons), but that the
> losses (due to compression also) may impact computer image analysis.
> 
> When describing the JPEG compression algorithm:
> "The reason for doing this is that you can afford to lose a lot more
> information in the chrominance components than you can in the luminance
> component: the human eye is not as sensitive to high-frequency chroma
> info as it is to high-frequency luminance."
> So JPEG is no good for images with high transition in the chrominance
> alpha channel. 
> 
> Ok, keeping this in mind, I decided to move forward with JPEG.
> No I could use my custom library to compute beam profile, position, etc.
> But is there a standard package for image analysis I should know about?
> Or is everybody doing it there own way?

The Astronomical community uses 'Flexible Image Transport System' FITS
for their image data sets. more information at :-

http://fits.gsfc.nasa.gov/

> 
> Regards,
> --
> Emmanuel
> 
> 
> On Tue, 2007-04-10 at 13:48 +0100, Pearson, MR (Matthew) wrote:
> 
>> doesn't have a web server, and needs windows software to view the video.
>> There are software projects out there which can capture IP video, but
>> not sure what Linux support exists.
> 
> 
> 

regards
- --
Dennis Armstrong
Swiss Light Source WBGB/003         Tel.: (+41)-(0)56-310-5109
5232 Villigen, PSI                  Fax.: (+41)-(0)56-310-4413
Switzerland
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System