Epiphan VGA2USB and GBS8200 for old HP test gear - Page 1
Forum section: electronics / testgear

author: ironcurtain
author_rank: Regular Contributor
timestamp: June 03, 2024, 11:31:05 am
content: I made a sync separator board with a LM1881 for a GBS8200 video converter. The adjustments are easy (for monochrome set saturation and contrast to 99/max).The problem is the fps rate with the Epiphan VGA2USB capture card. It's tapping out at 4fps, and obviously the shifting numbers (dBm readings, spectrum analyzer plots, etc) are ghosting.I have tried several settings in the Epiphan software to no avail.Anyone else has/had similar issues with their capture cards for VGA) This is one of the older, now discontinued, models. All drivers and firmware are up to date.It's running on a recent gen Intel PC, so the system isn't complete crap. It should do >20fps just fine when a Pentium 4 was benchmarked back in the day to do ~7fps or more with the same card.

author: _Wim_
author_rank: Super Contributor
timestamp: June 05, 2024, 08:03:04 pm
content: What resolution are you running? Are you using the "VGA2USB" or "VGA2USB LR"? I am using the last one, and >20 fps is no issue.EDIT: I am not using a GBS8200, only using the VGA output ports of the various test gear I have with a switchbox in between. Goal is to make screenshots for documentation purposes.

author: _Wim_
author_rank: Super Contributor
timestamp: June 05, 2024, 08:14:15 pm
content: These are the settings I use.Connected gear:Ando AQ6140 Wavelength meterAnritsu 9710C OSAHP 70004A +HP 70951B OSAWorks great for this purpose.

author: mariush
author_rank: Super Contributor
timestamp: June 05, 2024, 09:16:24 pm
content: Well, I would guess that gbs8200 upsamples and sends 1024x768 or higher resolution.VGA2USB's framerate varies with resolution -https://www.avw.com.au/images/Epiphan/Brochure_VGA2USB.pdf:Update Rate (Frame rate varies depending on content.)Resolution Frames per second640×480 28.0800×600 20.61024×768 10.01280×1024 5.61600×1200 4.31920×1200 3.1Doesn't matter that you crop, the source resolution is still 1024 x something so your max will be 4-6 fpsalso note epiphan isn't particularly great for this as it supports only RGB16 (565) color space, not RGB 24 so you get only 65k colors in the first place.You'd get better results getting a VGA to HDMI/DVI converter and then use a dvi/hdmi capture cardex vga to hdmi converterhttps://www.ebay.com/itm/374288831868(no idea about quality)The cheap hdmi usb capture cards will capture and compress to h264 or mpeg2 or some compressed video and stream this compressed content to the pc so the quality may not be great. But they're literally 10-15$.Something not noname... Ugreen has a HDMI capture card that is around $40 :https://www.amazon.com/UGREEN-Ultra-Low-Streaming-Conferencing-Compatible/dp/B0CM9C91MK/If you're able to use a pci-e capture card, this one with 10$ starting bid (47$ buy now) may give you uncompressed raw hdmihttps://www.ebay.com/itm/156233165370Seems to be timeleak hd72B :http://www.timeleak.com.cn/EN/Product.aspx?id=662edit : seems to be using a hardware mpeg2 compressor, and can do up to 1920x1080 30p, 60fps maybe at lower resolutions...

author: ironcurtain
author_rank: Regular Contributor
timestamp: June 05, 2024, 09:45:15 pm
content: Gladly surprised this late night thread of mine grabbed some attention and got enough traction.I have the older VGA2USB, not LR model, it came from an ebay seller that obviously got it from some garbage bin sale (has a sticker for a middle school from the 'murican corn belt).I need to check tomorrow what settings I used. I was selecting 1024x768 inside the GBS display settings. Will try the settings suggested here and report back.Thank you all, the fps table per resolution was the true eye opener here. I'm surprised the performance is so piss poor for the price these things used to have.I also got a Chinesium VGA to USB converter board that obviously does some internal webcam-like function (can be used via VLC). I like the Epiphan because I can add overlays and such quite easily (and record).Another thing I want to try is using Amscope's software, since it works with normal media inputs too.

author: ironcurtain
author_rank: Regular Contributor
timestamp: June 05, 2024, 11:51:01 pm
content: Adjusted the resolution in the GBS settings down, and the settings in the Epiphan software. It's more usable now at 10fps.Did not seem to make a difference at 1024x768 though, but I will leave it at 800x600.I added custom VGA modes, that seemed to do the trick.Now the quest for an updated/available command set or tool to do GPIB commands.

author: _Wim_
author_rank: Super Contributor
timestamp: June 06, 2024, 05:27:59 am
content: Quote from: mariush on June 05, 2024, 09:16:24 pmThe main advantage of the epiphan it can do "custom" vga modes. For example the HP 70004A uses a non standard vga mode (1024 x 400, horizontal scan frequency 25 kHz, 60 Hz vertical sweep frequency), which did not work correctly on my no-name VGA grabber I once bought from Ali-express. RGB16 is more than sufficient I think for old test gear, many of which are even monochrome displays of 16 colors only...But I do agree that for standard VGA your suggestion is much better, certainly price-performance wise, as these epiphan LR cards still cost a fair bit compared with what you can buy on Ali-Express...