OBS has the limitation that it can not capture frame exact. This is due to the fact that it allows to combine multiple input streams to a single output stream where it does always a conversion to the configured output fps.

Well I found this:
https://inogeni.com/dvi-usb3-0/

It's suitable for VGA and DVI @ 640x480, but sadly states it requires USB 3.0; which could be resolved by a PCI-e USB 3.0 card but then that's more expensive than getting a C127.

raymangold wrote:

Going on startech's website for the PEXHDCAP, they don't seem to have 640x480 as a support resolution mentioned for 'PC' (guessing that means VGA and DVI). Have you actually got 640x480 capture working on that thing? And now I'm wondering if the successor (PEXHDCAP60L) supports 640x480; you'll note that it has more ICs so it presumably has more bandwidth capabilities.

Now I'm kind of curious after looking at the DGC103C. There has to be another analogue to this but with the functionality of both DOS resolutions and standard VGA and XGA resolutions?

Hey, I made a mistake in my previous post. It's not DScaler I use for lossless raw video it's VirtualDub (Dscaler does a similar job but it's a 32bit Windows XP program designed for TV capture and viewing).
I can confirm I'm getting 640x480 capture from the PEXHDCAP (v1) in both VirtualDub and OBS. I can also confirm good results with the x264 Video for Windows Library which now has some support for VirtualDub.

To capture I'm outputting VGA from a Voodoo 3 into a VGA splitter which outputs to; A-Monitor & B-PEXHDCAP via a vga to DVI adapter.
I'll post some recordings from the Datapath VisionRGB-Pro some time tomorrow.

W.

EDIT: I recorded some footage from the Datapath card https://youtu.be/NW9sV8y6Lfc
EDIT 2: After doing a little more testing and capture setting adjustment I've gotten a much better results using OBS. https://youtu.be/YVGqgcegtuM

https://youtu.be/sRANj8B6J0o - Quake 2 Captured at 640x480 on PEXHDCAP (WARNING TO HEADPHONE USERS!! Line in levels we're a little loud.)
https://sourceforge.net/projects/virtualdub/ - VirtualDub Video Recorder
https://sourceforge.net/projects/x264vfw/ - x254/h264 Video library with VirtualDub Support

This is a long thread so I'll just start with my plan and I can be corrected if anything is going to backfire on me.
Once my DOS machine is built I want to try capturing from it.

I have a Micomsoft SC-512N-L/DVI so I am thinking of trying to use a VGA - > HDMI converter - >Splitter so I can still use my monitor, and then feeding the other signal into my capture card.
Depending on the adapter I buy (audio, no audio etc) I can feed the audio in through the capture cards audio breakout cables, or pull it from HDMI as well.

Will likely capture with OBS or AmaRecTV

Hey Neco, If the VGA -> HDMI is a good upscaler too this sounds like it would work, things to bear in mind are:
Resolutions you want to record 640x480 or lower and the aspect ratio, 4:3?
What the HDMI converter does to that image, does it stretch, upscale, add borders and does it support the resolutions you want to convert/upscale?
The Micomsoft SC-512N1-L/DVI doesn't have a HDMI port but converting HDMI to DVI can be done with out a expensive converter just an adaptor.
Finally what resolutions the Micomsoft SC-512N-L/DVI supports (and frame rates).

Lots of people recomend VirtualDub for capture, but It does take along time to configure/get working right, and even then I'd recommend using another application for recording audio then sync it up after as VDubs audio sync is known to have its quirks. My recommendation is OBS as it's much easier to get configured and gives consistent results.

I don't like using Vdub for capture. too old / quirky. I don't have a complete list of resolutions but the SC-512N1 has been used a lot in the speedrun / other console recording communities and is highly regarded for its ability to capture all the way down to 240. It'll take pretty much almost anything you can throw at it Interlaced or Progessive I think.

As for any adapters, I would be trying straight adapters, no futzy scaler units or anything like that. The SC-512N1 comes with two HDMI -> DVI adapters and can even pull HDMI audio in through the DVI ports this way. It's a fairly versatile card and can record all the way up to 1080p @ 60fps. I don't know how many Hz it can run at with the lower resolutions though. Might be restricted to 60Hz overall

Sounds like a solid solution Neco! Please post some links to any videos you capture when you get setup. I'd be interested to see the results.
W.

Whiskey wrote:

Lots of people recomend VirtualDub for capture, but It does take along time to configure/get working right, and even then I'd recommend using another application for recording audio then sync it up after as VDubs audio sync is known to have its quirks. My recommendation is OBS as it's much easier to get configured and gives consistent results.

This is not a good comparison. OBS as well as VirtualDub have their limitations for sure and it strongly depends what you want to do.

The inability to capture frame exact of OBS induces stuttering. While a skipped frame at 60 fps might be ok every few seconds there are situations where this is really bad:
Imagine you have a oldschool source like a C64 that is captured by a capture card interlaced. You employ the Retro/Scandouble Deinterlacer to get back the ~50 fps. Even if you set the output fps to 50 fps it is not locked to the input 50 fps and they deviate slightly. If the actual input frame rate is slightly higher then OBS will skip an input frame every few seconds. However one input frame relates to two output frames due to the deinterlacer that results in missing double frames each skip. This is a rather bad overall behavior and most likely the reason merely all people capture from emulators. There is no simple way to fix this.

As for VirtualDub usually if you get Audio/Video desync you likely have misconfigured some settings. For me the worst limitation of VirtualDub is the lacking support for variable frame rate as well as variable resolution within a single video stream. This is mainly due to the age of the program. I haven't found some recent video capture application that can cope with this well though.

However I am open for recomendations.

Elianda makes many good points if frame exact capture is what you need heed his advice.

For my needs my capture hardware is an old analogue PCI card that seems to want to capture at 70hz at low resolutions, this combined with using the preserve input resolution, a 5ms buffer and yadif options in OBS give me good smooth capture, (bearing in mind I don't need perfect 100% accurate capture). See the footage in Edit2 of my earlier post for an example of this (or here https://youtu.be/YVGqgcegtuM).

Another thing to consider is what YouTube does when it compresses footage, only if you plan to upload I guess. Also file storage for recordings, OBS captures are well compressed and still at a reasonably high quality, where as VirtualDub recordings (x264) are still gigabytes for 5mins.

W.

The comment about frame stutter intrigues me. I have seen this across multiple programs, so I'm not sure what would make Vdub different in this case. I always assumed it was some weird quirk with my system though, but yes even at 60fps it is very annoying. I can detect when it happens and sometimes its a few frames in a row, or a couple frames and a short gap and a couple other frames. etc.

I haven't really tested it with games other than Dirt Rally though, which is why I've let it slide because that game does have its own quirks with FPS (if you turn off Vsync it becomes choppy its hilarious).
But its weird, I've seen choppiness even when capturing with NVENC via OBS doing the job. I did try shadowplay but it produced VFR footage which is ridiculous and no good for editing.

I've seen stuttering in AMARectTV recordings as well. Perhaps it was a little improved, but overall, still stutters.

But maybe I'll give vdub another try. Any general tips on setup? I can sort the codec stuff out (x264vfw is easy enough).

Well I use it with an Epiphan card usually but my timing setting are:

-> Drop frames when captured frames are too close together
-> Insert null frames when captured frames are too far apart
Null frame burst limit: 1

Resync mode: Do not resync between audio and video streams

Audio latency determination: automatic
number of audio blocks to use at start: 30

Do a test capture and look that Frames dropped/inserted stay at zero. Especially dropped should not happen. If your set frame rate is slightly too high then every few mins inserted may increase by one. If you set frame rate fits then both will stay at 0.
Also the Sync/ Current error should not increase. If it does either your video or audio timer is running off. Usually this should not happen but there exist flaky drivers. You may try to set 'Use audio timestamps when available' and check if it stays constant now.

Whiskey wrote:

https://youtu.be/YVGqgcegtuM

Well the first thing visible is that in text mode the characters seem to have varying vertical line widths that indicate a too low number of horizontal sampled pixels.
Also on the still images, e.g. in Doom pixel glitches occur where something with your output card seems to be wrong/broken.

elianda wrote:

Whiskey wrote:

https://youtu.be/YVGqgcegtuM

Well the first thing visible is that in text mode the characters seem to have varying vertical line widths that indicate a too low number of horizontal sampled pixels.
Also on the still images, e.g. in Doom pixel glitches occur where something with your output card seems to be wrong/broken.

The pixel line glitches are just from the output of the Voodoo 3 3000 I'm using, it's getting on a bit and has been used a lot for many years.
As for the text in the dos prompt that's the de-interlacing method which makes the text do that (Yadif - Using no/other methods with point sample enhancement yeilds much sharper pixel 1:1 results for dos prompt text), but i feel makes moving video a little smoother in my opinion.

By no means am I a professional, I'm just doing this for a hobby and for fun. W.

So your capture card delivers the regular DOS text mode as interlaced 35 Hz?
Then the mathematical correct deinterlacing method seems to reframe the stream instead?
e.g. in Avisynth notation:
video=AviSource("mycapture.avi")
video=SeparateFields(video)
videoE=SelectEven(video)
videoO=SelectOdd(video)
video=Interleave(videoO,videoE)
return video

Other deinterlacers that compensate for specific properties of video standards such as PAL or NTSC are likely a wrong application in this situation.

Won't you end up with aliasing / shimmering if you do it like that though? Or is that not really an issue with PC captures?

Neco wrote:

Won't you end up with aliasing / shimmering if you do it like that though? Or is that not really an issue with PC captures?

Could you specify why aliasing / shimmering should be introduced?
The described recipe is just the mathematical inversion of what the capture card does when it captures a progressive signal interlaced. The interlaced fields are interleaved again on a frame basis.

I was probably confusing it with bob interleave (is what you did weave?)

Interlaced video isn't really my strong suit, this is just me asking dumb questions in an attempt to learn something. Still I wonder what it would look like after going through QTGMC 😁

From the input data this wouldn't make any sense, however you can just generate some interlaced material from a progressive video and try it out yourself.

More interesting would be to find out why his card captures progressive VGA input as interlaced and if with some options set the capture can be done progressive maybe.

I'm looking at VGA - > HDMI adapters/scalers and so far the lowest resolution support I've seen (listed) on a product was 640x480 😵

There is a supposedly good VGA->DVI scaler out there by Gefen (discontinued) that is said to run 320x200 but its prohibitively expensive for me, even used. For the prices they want I could probably buy an XRGB mini framemeister and get a lot more functionality out of it for use with other things. (not sure if it will take input from a computer or not)

320x200 Mode 13h = 640x400@70Hz to capture cards and analog to digital convertors. It should be supported by most anything out there.