detector liveview page

[rerpha]

As a user I would like to be able to see my detector's live view on the web dashboard. This does not need to be live, just needs to be updating every few seconds.

Some technical considerations:

• live view in the GUI is AreaDetector generated, but accessing the entire detector may consist of a large array read. You can set the data of a html image to any value so performance shouldn't be an issue on the frontend.
• we may need to throttle this to avoid saturating any networks - does this need to be done on the EPICS end?
• this should probably be a separate page which is linked to/from the main instrument status screen to avoid cluttering the UI.

[Tom-Willemsen]

• If we're just doing this as an image - where is that image hosted (that is externally-accessible)?
• Do any instruments have more than one detector live view they'll want to see on the web dashboard?

[FreddieAkeroyd]

See ISISComputingGroup/IBEX#8749 for underlying areaDetector work

[rerpha]

I think we should explore just getting the array data from epics first (if they aren't that big?) rather than worrying about a service which hosts the jpegs? or you could "jpegify" the array data so it's compressed first etc.

[Tom-Willemsen]

We were going to try to configure dbwr anyway for some eurotherm stuff, so that seems like a sensible starting point. Only concern is how big the arrays are; all the intermediate gateways will need a big enough EPICS_CA_MAX_ARRAY_BYTES and we'll probably need to turn the max array size in pvws up significantly.

[FreddieAkeroyd]

I did have https://github.com/areaDetector/ffmpegServer working once, had a feeling that didn't have to stream and so may be a more direct way to just get an image

[Tom-Willemsen]

Areadetector probably has a rebin-type plugin to make the arrays smaller (e.g. limit to 100x100px) for DBWR to consume.

[mducle]

Would this be an opt-in feature or present on all instruments? I think there are some instruments with very large detectors (e.g. LET, MERLIN) who would not need a live detector view (as the count rate is slow enough and the data usually requires a reduction step to be interpretable so a live view will not be so useful) - so if you exclude those the data requirements might be more manageable.

[Tom-Willemsen]

@mducle for instruments which need a reduction step, https://reduce.isis.cclrc.ac.uk/fia is the way to go (as you're well aware...)

[FreddieAkeroyd]

https://github.com/areaDetector/ffmpegServer/blob/99f93d900784d45dabc62d6b03f68a7a6fdaeabd/ffmpegServerApp/Db/ffmpegStream.template#L197 suggests ffmpegServer may provide a jpeg URL that the dashboard could use

[GRyall]

Right now this is a single request - we need to prioritise this against our other work.