PAL/NTSC video capture - need a line or two for LTspice sim - Page 1
Forum section: electronics / projects

author: tom66
author_rank: Super Contributor
timestamp: August 03, 2012, 10:33:49 pm
content: I am looking to experiment with some video processing circuits in LTspice.Perhaps the best way to do this is to capture an analogue video signal (PAL or NTSC) and use this as an arbitrary waveform file.Unfortunately I don't yet have a DSO. (Maybe soon - when my DS1102E arrives.) If anyone has the capability to capture a few lines of PAL video for me, I would much appreciate it. I don't think a whole frame is possible, unless ~43Mpt scope was used (for the colour burst.)Or any other way of generating video signals on a PC to import into LTspice?Thanks!

author: vk6zgo
author_rank: Super Contributor
timestamp: August 04, 2012, 04:02:15 am
content: I don't know a lot about LT spice,but I do know a considerable amount about video signals,& I think you may be in for a disappointment in trying to capture a video signal with a DSO to do anything other than those things a 'scope is intended to do.I think you would be better trying to either create the video signal internally to your PC,or use simple waveforms to check individual characteristics of your device,For instance,you can check the steady state response of the circuit with a swept frequency signal,& the rise time with a simple square wave pulse,or you can probably simulate a 2T pulse for the same purpose.A 50Hz (or 60Hz) square wave signal will check your LF response.It is only when you get into timing critical tests,or those which require a "real" video waveform that you will be in trouble.Clamp circuits,& anything to do with manipulating the video information fall into both of these categories.

author: tom66
author_rank: Super Contributor
timestamp: August 04, 2012, 08:29:04 am
content: Quote from: vk6zgo on August 04, 2012, 04:02:15 amI'm not particular interested in frequency response, as I will be using op-amps with a decent frequency response (I will test this in the simulation, and I will mostly use video amplifiers.) More, I'm looking for ways to test DC restoration, colour burst separation etc.

author: vk6zgo
author_rank: Super Contributor
timestamp: August 04, 2012, 09:24:28 am
content: On second thoughts,it maybe depends on how LT spice does its arbitrary waveforms.Does it take the data ,say from a DSO directly,& convert it directly,or actually work from the screen graphics on the PC?If it does the former,you could maybe use a video "grabber"instead,& if the latter,maybe do it from a picture (line drawing) of a video waveform.As I said,I know zilch about LT spice!Are you sure they don't have a video signal available,either themselves or a third party one?

author: jahonen
author_rank: Super Contributor
timestamp: August 04, 2012, 09:40:46 am
content: Here is some data in csv format, hopefully you can use it. First one is 125 MSa/s and another one 2 GSa/s. The data was unfortunately too large file to attach here, but you can download ithere.First one looks like this:and second one like this:Regards,Janne

author: tom66
author_rank: Super Contributor
timestamp: August 04, 2012, 10:25:07 am
content: Thanks very much for these!