Duck science.

Factorio (Space Age expansion).

Also, if applied recursively, it approaches 2:

deleted by creator

So, I bought an EasyCap device and ran some tests. I encountered a few things that I don’t quite understand, and I would really appreciate your input!

I used a test VHS tape that I purchased at a thrift store (I’m not 100% sure if it’s NTSC or PAL, but I’m decently confident that it’s NTSC) (I’m also not sure what its aspect ratio is — I think it’s either 1.33:1 or 4:3). I’m playing the tape in a PV-D4745S-K VCR. I have the composite out of the VCR going into the aforementioned capture device which is connected to a computer running Arch Linux.

First, I used the following ffmpeg capture settings:

ffmpeg -i /dev/video2 out.mkv

After capturing a short snippet of the test tape, I probed its metadata with ffprobe -i out.mkv, and saw that it was strangely in 25FPS, and 720x576 (which caused the video to be stretched vertically slightly), which is PAL. So, somehow the NTSC VHS being played in an NTSC VCR was being converted to PAL. In addition to that, the colors in the video were very overexposed. I tried a bunch of different manual settings like specifying interlacing with -vf "interlace", -standard ntsc, -vf scale=720:480, -vf fps=29.97, -standard NTSC, and none of them solved the issue. I then came across this answer on StackOverflow which stated that capture cards themselves have settings for the video feed, and ffmpeg can modify them with the -show_video_device_dialog true option. From the ffmpeg documentation:

show_video_device_dialog

If set to true, before capture starts, popup a display dialog to the end user, allowing them to change video filter properties and configurations manually. Note that for crossbar devices, adjusting values in this dialog may be needed at times to toggle between PAL (25 fps) and NTSC (29.97) input frame rates, sizes, interlacing, etc. Changing these values can enable different scan rates/frame rates and avoiding green bars at the bottom, flickering scan lines, etc. Note that with some devices, changing these properties can also affect future invocations (sets new defaults) until system reboot occurs.

Unfortunately, when trying this option, an error popped up saying that the option was unrecognized. After some digging, and prompting ChatGPT, I found that apparently that option is Windows only as it relies on Windows’ “DirectShow system”. The way to modify it in Linux is to use the Video4Linux2 framework, which is controlled with v4l2-ctl. So, I ran the following:

v4l2-ctl --device=/dev/video2 --list-formats-ext

which showed the following entry:

...
[0]: 'YUYV' (YUYV 4:2:2)
    size: Discrete 720x480
...
        Interval: Discrete 0.033s (30.000 fps)
...

So it is able to output NTSC — ie 720x480 at 29.97fps (I guess it rounds up the fps for whatever reason). So I then tried

ffmpeg -f v4l2 -video_size 720x480 -i /dev/video2 out.mkv

and it was able to output the video at 720x480 29.97 fps as desired, and the colors were no longer super overexposed. Using the -vf "interlace" flag, I do seem to also be able to capture interlaced video, so it also doesn’t force progressive which is nice.

I thought that the capture card would be able to just autodetect what the input resolution was to allow ffmpeg to record at that, or at the very least, I would expect that specifying NTSC in ffmpeg would force the standard, but neither of those worked and I’m not sure why. There’s also still an ongoing issue of the video being zoomed in/cropped slightly (I verified this by comparing against online sources of the same video (some were a VHS rip, others from non-VHS sources)). I tested the VCR’s output on a regular TV, but unfortunately the TV forced 4:3 and cropped it even more, so I wasn’t able to make a perfect comparison, though that was only additional horizontal cropping — the vertical cropping from before was still present. To be able to verify that, I’ll have to pick up another test VHS tape to see if perhaps the test VHS tape that I currently have was just recorded in a cropped format.

libertarians aren’t a thing

[Libertarians] are republicans that are too embarrassed to identify as such publicly

Be careful to not make hasty generalizations.

To be fair, Libertardians also care about lowering the age of consent!

Based on what are you making this claim?

being libertarian is only marginally less embarrassing [than being a Republican] anyway

What about libertarianism is embarrassing to you?

Why are so many of those who claim that they’re libertarians not actually libertarians?

It seems to be an EasyCAP clone, there are several devices in this form factor with different chipsets.

Good to know! That link has a lot of good information.

This capture device seems to be labeled as “BR116” based on photos in reviews, which can help identifying the chipset. BR116 is sold by Conrad and its manual by them mentions “STK1160” in a screenshot, so this Amazon one most likely also uses the STK1160 chip, which was one of the worst ones in this timebase stability test (which means it has no TBC). However, it’s alright if your VCR is a late model that already does TBC internally.

Noted! I will keep this in mind.

I came across this video about digitizing VHS tapes [1]. It talks about hardware to use, and hardware to avoid [1.6]. One of the examples that it gives for hardware to avoid seems to be a clone of the device that I was looking at on Amazon [1.2]. The rationale for why it should be avoided was that it doesn’t pass both fields of the interlaced video through independently [1.1]. Though, you have mentioned that it’s fine to capture the video interlaced, so perhaps this isn’t a big deal-breaker. The capture cards that the video recommends are:

• IO-Data GV-USB2 [1.3]
• StarTech.com SVID2USB232 [1.4]
• Dazzle DVC-100 v1.1 [1.5]

Get an actual composite capture card for the job.

Ha, honestly, I wish that I would’ve done this to begin with. It’s way cheaper, and simpler to get the one composite capture card rather than converting composite to HDMI, then capturing HDMI. I’m honestly not entirely sure why I did the latter — perhaps it’s because I was under some presumption that such a device wouldn’t exist (which, now, I realize is an obviously silly assumption to make). I found this one. It’s still just a generic capture card, but it’s a direct composite capture. Do you think that it would suffice?

Check that the output is indeed interlacd

Is it possible to see this in OBS? I see an option to select an interlacing technique if I right click the scene

Look at stats/logs to see of any frames are dropped and investigate if it’s just the 59.94 Hz compensation

Are you referring to “stats/logs” within OBS?

make sure to disable auto-gain or else quiet sections will get boosted like crazy, increasing the noise.

If you are referring to a toggle on the capture card or the converter, neither have a button for that, so I think my setup is fine in that regard?

This was very informative! Thank you for your comment!

you should check that the video output is actually at [59.94 Hz]

How does one measure the input frequency of the video feed? I’m not aware of OBS being able to monitor the frequency/refresh-rate of individual input devices, but I could certainly be wrong.

Don’t use the converter if it cannot output 480i or at the very least 480p! Scaling should happen during playback, the files should be original resolution.

I looked on Amazon again, and it seems that every converter being sold only outputs 720p, or 1080p — none of them simply repeat the input resolution, eg 480p or 480i. Would you have a converter in mind that would accomplish this?

I’d just clean the VCR after every tape if I suspect mold. You’d still need to clean the cleaning VCR after every tape to avoid cross-contamination

Do you have any resources that you would recommend for proper cleaning of a VCR?

Ah, so it does [1]. Apologies! Perhaps another older Thinkpad has a 12" screen? From what I’ve heard, and from my experience with my own T460, they’re usually pretty solid laptops, so if you could find one with the specs that you are seeking, I would say that it’s worth considering.

Older Thinkpad (eg T460)?

vhs-decode

This is a very cool project! Thank you for sharing it!

Why a separate VCR for cleaning tapes?

I was just thinking that the cleaning process might damage the VCR (as one is rummaging around in its internals [1]), so it’d be better to use a worse quality VCR for cleaning, and a good quality one for digitization.

you should definitely not use default deinterlacing techniques for the video

What “default deinterlacing techniques” are you referring to?

you should […] especially not [use deinterlacing techniques] built into these generic dongles

How do I find out that information for the 2 things that I purchased (mentioned in the post)? How would I even control that? Only the composite to HDMI converter has a single switch from 720p to 1080p. I don’t see anything else that would control what interlacing technique is used.

Capture [the video] interlaced, preferrably as losslessly as possible

What method do you recommend to accomplish this?

use deinterlacing software where you can fine-tune the settings if you need to.

Is this possible in OBS?

TBC can obviously be done in software if you have the raw composite or head signal but that is not possible with the capture cards you have.

If I did want to capture the raw signal, do you have any methods and/or tools that you would recommend to accomplish this?

Dang, that’s pretty neat! Man, there’s probably going to be some funky bugs with legacy code getting included into Rust.

I thought Rust already had several different methods for interacting with C++?

Oh? Would you mind sharing them? It would be absolutely fantastic if such a thing existed and is mature enough to be practically used.

Personally, I have little interest in learning or dealing with C++ solely for the sake of developing KDE applications. I would much rather use Rust.

Imo, restricting the languages that can be used for app development cuts out large swaths of developers who would otherwise be eager to develop software for the project. I’m sure there are some who wouldn’t mind picking up C++ for this cause, but I’d wager that they are a minority. Gnome beats out KDE in that regard, imo, as GTK has bindings and documentation for many languages.