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Standardised Way To Test Oscilloscope Screen Update Rate

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bdunham7:

--- Quote from: EEVblog on April 29, 2024, 11:01:46 pm ---I like pdenisowski's "pixels changing" definition, so any test source need to have "pixels changing" at a fast enough rate to make the measurement possible.

--- End quote ---

You'd just have to ensure that the waveform rate was higher than the screen rate so that you'd expect new information to be available at every screen refresh.

What is bit  confusing about the video I posted is that the waveform update is set at 60/s (using line trigger) and the 60fps video shows a display update (pixel change) on each and every frame yet there are multiple traces showing.  This is why I was saying that 'screen rate' or 'screen update' may not be simple, clear-cut concepts.

joeqsmith:

--- Quote from: bdunham7 on April 30, 2024, 02:21:46 am ---You'd just have to ensure that the waveform rate was higher than the screen rate so that you'd expect new information to be available at every screen refresh.

What is bit  confusing about the video I posted is that the waveform update is set at 60/s (using line trigger) and the 60fps video shows a display update (pixel change) on each and every frame yet there are multiple traces showing.  ...

--- End quote ---
Your video requires some codec I don't have. 

The nice thing when using the camera, you may be able to see more detail into how they are updating the screen.  At 1000fps capture and only a 30fps screen refresh, it's plenty of data.  I purposely used >MHz signals, normal trigger, and very small data sets in an attempt to make sure they were updating the screen as fast as possible.  With the camera, it appears that the scope is not periodically refreshing.  It seems to stutter or stall at times and then plays catch up.  I had turned off all the readouts and such and set the scope software to the highest screen priority but with Windows not being a RTOS, I am not too surprised. 

Kosmic:

--- Quote from: joeqsmith on April 30, 2024, 01:05:10 am ---I placed a stopwatch in front of my scope's display.  Connected to a RF generator set to sweep from 5M - 100M.  Very small data set.  Norm trigger.  All processing turned off.  Camera set to 1000fps.   Recorded for 1sec.  Manually counted each screen update. I measured a pathetic 30fps.  It's an 18 year old PC and based on how poorly it handles the X-Y music, not surprised.

--- End quote ---

Not long ago (10 years?), 30fps was pretty standard for most application on a PC. Now these days it has increased to 60 - 120 fps for dynamic and responsive application. Nevertheless, 30fps is still present. For example you still find a lot of video games running at 30fps.

radiolistener:
I think it will be hard to determine refresh rate from high speed video camera capture of the display pixels change, because display has some limited pixel change speed. If there is a way to attach external display it will be better to analyze video signal.

bdunham7:

--- Quote from: joeqsmith on April 30, 2024, 12:47:43 pm ---Your video requires some codec I don't have.

--- End quote ---

That's Windows pissing in your ear and telling you that it is raining.  HEVC (h265) has been around for quite a while now, but MS still wants a fee to let you use it.  Download VideoLan if you want a decent video viewer.

https://www.videolan.org/vlc/download-windows.html


--- Quote ---
It seems to stutter or stall at times and then plays catch up.  I had turned off all the readouts and such and set the scope software to the highest screen priority but with Windows not being a RTOS, I am not too surprised.

--- End quote ---

Those stutters and stalls are the main thing that makes a display annoying and not 'live'.  I think a consistent 30fps might be marginally sufficient for most people in most cases just like video, but throw in 5 consecutive missing frames every two seconds and everyone will hate it.

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