Counting photons with an MPPC

Jan Panteltje wrote in news:qjm8ke$vcp$ snipped-for-privacy@dont-email.me:

Your machine must be an old 32 bit Linux box or other such old crap, and you want new software to run on it.

VLC is merely a front end for ffmplay and ffmpeg, idiot.

You are a true idiot. They saw you coming and now they ream your ass at every chance.

It should be pay and play all month, not pay for each byte. Sounds like a bunch of greedy bastards over there.

Same here,XP SP3 and VLC Media Player 2.0.8 Twoflower

I have some files copied from a security NVR recorder; those files come in pairs: *.d which is big enough for te video, and *.i which seems to be like a directory. The system has a player and an AVI converter; both of which needs to see the *.i file to work. Do you have any suggestions of how to get VLC to accept and playtem?

Thanks

try opening one of the *.d with vlc if that doesn't work look inside the *.i

Robert Baer wrote in news:e0r8F.328488$ snipped-for-privacy@fx37.iad:

the d file is the data and the i file must be the info to play it. Kind of like a header. Probably proprietarily encrypted.

So contacting them might yield info but they usually blow off folks wanting access to their files without their hardware. I dunno... just conjecture.

When one rips a bluray DVD, there is a way to do it that yields like a 36GB set of files. It is like three files, but it contains the java and such so that the menus can be played, etc. My PC needs to be able to run that file at like 10Gb/s to play it though.

Mostly folks make those big files so that any downconversions they do are done from the best source stock.

But no. I do not really know much about the file types etc. out there.

My mention about video and Gen Inst. was real video on cable systems, not captured files and such. And that was a while ago so I am likely not up on the latest either, though I see what folks use by simply DLing the files and seeing what they have available.

So I know what h.264 is but knowing what is best, etc. and for what platforms, etc. Not this kid. I grab what I know works but that is the extent of it on file types.

On Aug 24, 2019, Sjouke Burry wrote (in article):

The problems I had were on MacOS, not Windows. See separate posting for details.

Joe Gwinn

• Did that before my posted query. On the *.d, VLC search bar showed a tapered, colored bar scanning back and forth for 20 seconds, and then gave up.

Thanks.

• Exactly. PITA.

• Sent then a query.. Still waiting.

• These format(s) are at least 5 years old or so..

Thanks.

That means that vlc looked all through the file and didn't find anything that it recognised as video. I'm not sure how to proceed.

Grin. I have seen reports of single photon detection eff of ~75%.

George H.

You can crank up the bias to improve the detection efficiency, but the false count rate goes through the roof.

Cheers

Phil Hobbs

Thanks.

That is surprising, semiconductor gamma-ray detectors (e.g. HPGe) have the best energy resolution to date. Obviously this being a small device its energy range would not go high enough so there is likely no practical application for that.

On a side note, what throughput did you manage? (counts/second after which the counts which make it through start to decline). I recently did photon counting using a good old PMT (well not old really, a fairly new Hamamatsu model), easily got > 20M cps which was plenty for the application (a TLD reader, yet to be announced, don't look for it yet on the website, perhaps next week :).

Dimiter

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For some of the SPAD's one photon causes the whole capacitance to discharge (by the over-voltage)... another photon before it recharges is likely missed.

George H.

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They all have a certain dead time, given that the events are stochastic this will always happen, how often will depend on the input count rate and on the amount of dead time (which is mostly produced by the electronics after the detector, the one the detector produces is typically negligible but it is there allrigh. Reporting the correct overall dead time is an integral part of a measured gamma spectrum and it is non-trivial, a competitor call that "zero dead time", we do it by DSP software and call it nothing, just "dead time" as it is certainly not zero as their name implies (their results are also correct, just not zero, more or less the same as ours)).

However this has little to do with energy resolution, the pulse height depends on the number of electrons the photon has managed to kick into the detector which is proportional to the photon energy. In fact HPGe (and Si) detectors are *very* linear.

Dimiter

====================================================== Dimiter Popoff, TGI

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OK, I don't know about gamma's... but I can imagine you can get multiple electrons. For visible stuff with Si photodiodes in the linear range one photon = one electron. When run in the avalanche region, you get a X-electrons per photon... where X is the gain, and is stochastic. And then run in the geiger-mode (Spads), a photon discharges the whole diode capacitance , and you get pulses that are all basically the same height. (The only time the pulses are shorter (in amplitude) is when you get a phot on triggering the spad, while it's still recharging from the previous event. And finally there are these MPPC things that Phil is using. I've never use d one of those.. but IIUI you have an array of spads, and then can again have different peak heights if there is more than one photon... you can see som e of those double pulses in Phil's video.

George H.

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That's not a huge issue with these ones, at least not in analogue mode. The ir pixels are only 50 um square, so they have lots (3400-odd iirc) and they recharge again in about 20 ns. Each one dumps about 2 million electrons, s o the saturation current is about 55 mA. At 53 V bias, the poor thing would be dissipating almost three watts, which would turn it to lava.

Cheers

Phil Hobbs

heir pixels are only 50 um square, so they have lots (3400-odd iirc) and th ey recharge again in about 20 ns. Each one dumps about 2 million electrons, so the saturation current is about 55 mA. At 53 V bias, the poor thing wou ld be dissipating almost three watts, which would turn it to lava.

And ruin your day. :^) I assume you have some current limit in the supply line that will stop that from happening... when some tech open's the unit up to room light.

GH

I get it, in fact it is obvious there would be no energy resolution to speak of. The energy range for visible light is below 2eV, the best HPGe detectors have a resolution of hundreds of eV at low (122keV, 59.5keV) and some xray Si detectors go down to around 100 eV resolution. I just did not think of how narrow an energy range we were talking about :-).

Dimiter