Improving the end result - VHS captures

[nbatapes]

Hello!

I have read these forums for years, but posting for the very first time now! To make a long story short, I have literally thousands of old VHS cassettes, mostly consisting of NBA Basketball games from the 1990's. After reading a lot from others on here, I think I've got the quality to a decent level (see sample), but I'm wondering if anyone could advise as to potential improvements?

Btw, I use an AG-1980 VCR + TBC and capture in VirtualDub.

The script used on this clip was the following (edited after earlier question):

AviSource("Test Clip.avi")
ConvertToYV12(video)
AssumeTFF(video)
ColorYuv (video, autogain=true)
QTGMC(video,Preset="Placebo", SourceMatch=3, Lossless=1, NoiseProcess=1, NoiseRestore=0.0, Denoiser="dfttest", DenoiseMC=true, NoiseTR=2, Sigma=4.0)
Crop (video, 4, 0, -12, -8)
Spline36Resize(video,720, 540)

Anyway, let me know what you guys think - thank you!

[lingyi]

Won't comment on your video since I don't have the discriminating eyes of some of the others here, but will congratulate you on your choice of hardware. The critical missing piece is what type of capture device are you using as they may be a key component to improving your captures.

[nbatapes]

Thank you...I use the ATI TV Wonder 600 USB to capture

[davexnet]

Thank you...I use the ATI TV Wonder 600 USB to capture

Can you post 10 seconds of the raw capture?

[dellsam34]

The frame is stable but too much noise reduction that blurs the details, VHS is noisy in nature and trying to eliminate that noise always come at a price. Also the resolution is not legal.

[nbatapes]

Thank you...I use the ATI TV Wonder 600 USB to capture

Can you post 10 seconds of the raw capture?

Yes...please see attached and thank you

[DB83]

You may wish to post your full script.


You have obviously cropped and re-sized and as already pointed out the re-size is on the vertical instead of on the horizontal (you should keep the lines as 480 not resize to 540)

[nbatapes]

You may wish to post your full script.


You have obviously cropped and re-sized and as already pointed out the re-size is on the vertical instead of on the horizontal (you should keep the lines as 480 not resize to 540)

Thanks...yes, below is the full script:

AviSource("Test Clip.avi")
ConvertToYV12(video)
AssumeTFF(video)
ColorYuv (video, autogain=true)
QTGMC(video,Preset="Placebo", SourceMatch=3, Lossless=1, NoiseProcess=1, NoiseRestore=0.0, Denoiser="dfttest", DenoiseMC=true, NoiseTR=2, Sigma=4.0)
Crop (video, 4, 0, -12, -8)
Spline36Resize(video,720, 540)

[DB83]

Thnx.


I'll leave it to the real experts to comment but apart from the resize (should be 640,480) I would expect a line to return the video to interlaced.

[davexnet]

Thnx.


I'll leave it to the real experts to comment but apart from the resize (should be 640,480) I would expect a line to return the video to interlaced.

The two main things I noticed is that you should have

ConvertToYV12(interlaced=true)

Also, the capture is PC range, 0-255 Vs. normal TV range, 16-235
The method to fix this,

Levels(0, 1, 255, 16, 235, coring=false)

leaves it a little washed out.

This may suit your script better:

ColorYuv(levels="PC->TV",autogain=true)

You may well get further suggestions

[oln]

You would want assumetff before convertoyv12.
Also be careful with autogain, it can cause flickering, it's better to use the histogram function (at the end) and manually adjust levels to be in range instead.

[nbatapes]

Thnx.


I'll leave it to the real experts to comment but apart from the resize (should be 640,480) I would expect a line to return the video to interlaced.

The two main things I noticed is that you should have

ConvertToYV12(interlaced=true)

Also, the capture is PC range, 0-255 Vs. normal TV range, 16-235
The method to fix this,

Levels(0, 1, 255, 16, 235, coring=false)

leaves it a little washed out.

This may suit your script better:

ColorYuv(levels="PC->TV",autogain=true)

You may well get further suggestions

Thanks for the help!

[ugnaught]

Don't crop to 640x480, that is just throwing away resolution for no reason other than to hit a 4:3 AR.

You're resize to 720x540 is fine. Both are true 4:3 without having to push DAR. You are recording at 720x480, better to stretch the vertical than cut the horizontal.

Unless you are really trying to keep filesize down, then by all means toss some pixels in the bin.

[DB83]

I am not going to get in to a lengthy discussion about the nonsense I just read but just consider the following.


1. The effective resolution of NTSC VHS is 352 * 240 pixels.
2. The capture device grabs 720*480 pixels, including 16 pixels (720 - (352*2)) which has actually then been cropped away. So even going back to 720 stretches slightly on the horizontal.
3. Then just consider how that VHS appeared on your CRT display. 480 lines and no more than an effective width of 640. Make those 480 lines now as 540 then you effectively make everyone taller and thinner (all beit slightly) than they really are.


The OP has not stated his final format since we only really see the archival version. And I do not buy in to any argument that 540 vertical pixels would upscale better on a HD display. In fact it may even highlight the 'taller and thinner' issue all the more.

[ugnaught]

I appreciate you calling my post nonsense. Off to a good start.

Capture VHS at 352 X 240. Then capture the same tape at 720 X 480.

Put them side by side. Compare the images with your own eyes. Not even close.

The year is 2020. Why toss any detail out of the captured VHS image? Is the year 2002? Are we trying to conserve space on our 40gb hard drive?

But don't just take my word for it.

Canadian National Archives recommends capturing at 720 x 486 for digitizing VHS in preservation quality.

https://www.canada.ca/en/conservation-institute/services/conservation-preservation-pub...deo-tapes.html

Hmm, maybe let's take a look at the US National Archives site. Let's see if they recommend 352 X 240, or maybe 640 X 480?

https://www.archives.gov/preservation/products/products/vid-p2.html

Huh, they also recommend 720 X 486 for analog to digital captures. Weird.

Maybe somebody from this forum should email them and explain to them that 352 X 240 is really the "effective resolution" and they are wasting their time.

edit:

480 lines and no more than an effective width of 640. Make those 480 lines now as 540 then you effectively make everyone taller and thinner (all beit slightly) than they really are.

The stretching to 540 is for a 1:1 pixel aspect ratio while also maintaining a 4:3 AR, keeping your 720 horizontal resolution, and not messing with the DAR. Some people report issues with playback devices displaying everything at a 1:1 PAR, in which case 720x480 looks stretched horizontally as it is now closer to 3:2.

But some people don't want to lose any image information at all, to include cropping the 720 to 640, but still maintain a 4:3 AR.

So some people just make their videos 720x540 (or 544) and none of that becomes an issue. You aren't losing any quality by doing that (other than the re-encode itself).

Nobody becomes "thinner".

720 X 540 = 4:3.

720/4 = 180.
540/3 = 180.

[dellsam34]

Resizing 480 to 540 by capturing standards is disastrous, The reason why it's okay to resize horizontally and not vertically is because analog video does not have a pixels structure in the H axis, It was set to 704 by D1 standard in the digital domain and 8 pixels on each edge for safety which is 720 pixels. But has exactly 525/625 (NTSC/PAL-SECAM) scan lines in the V axis, if we take out the synch and timing signals we will be left with about 480/576. While technically you can resize to any resolution you want the methods used are just mathematical approximation and always end up with quality loss (usually in a form of details loss).

There are instances where you have to resize such as social media sharing but if you are going to do that may as well resize to a bigger count like 1440x1080 The outcome will be less damaged than a very close resolution like 540. 1080:480 is 2.25:1 pixel ratio, 540:480 is only 1.12:1 pixel ratio. The bigger the ratio the better the math and the approximation jitter.

[ugnaught]

While technically you can resize to any resolution you want the methods used are just mathematical approximation and always end up with quality loss (usually in a form of details loss).

That tracks and I get what you are saying. When you are changing the resolution by such a small amount the algorithms used have hard choices to make.

The reason why it's okay to resize horizontally and not vertically is because analog video does not have a pixels structure in the H axis

Once you have captured analog video to 720 X 480, it is no longer analog video. It is digital. The capture card and codec used already made mathematical approximations and did its best job at translating that analog data into 720 pixel horizontal.

The H axis pixels are set. They are no longer theoretical analog lines.

So the resize to 640 H, if we are still following this logic from above, is just as disastrous as changing the V. The same small change puts the same burden on the resizing script to make the some tough choices.

There are instances where you have to resize such as social media sharing but if you are going to do that may as well resize to a bigger count like 1440x1080 The outcome will be less damaged than a very close resolution like 540. 1080:480 is 2.25:1 pixel ratio, 540:480 is only 1.12:1 pixel ratio. The bigger the ratio the better the math and the approximation jitter.

That would likely be the preferred method in any case then. Go big or go home, I suppose.

[dellsam34]

Once you have captured analog video to 720 X 480, it is no longer analog video. It is digital. The capture card and codec used already made mathematical approximations and did its best job at translating that analog data into 720 pixel horizontal.

No, Not really, The analog information is retained even after digitizing, Vertically every pixel contains its own information captured from the analog source, Horizontally not so much, Several pixels can be considered as one analog state of change in luma signal, In other words the horizontal resolution is so low (about 200 changes in luma) which makes 704 is about 3 and a half times the native luma definition, So resizing to 640 won't affect the overall quality that much.

[Eric-jan]

Some good de-interlacing would be a great improvement, if you want to view this on a LCD/TFT/OLED screen..
indeed addition of reworking to the picture will bring down the resolution more, and this is the main problem of the VHS resolution, if there's external interferrence you should leave that alone, but there seems not to be much of that.
Don't think you should putt too much energy in further reworking, de-interlacing is all what it needs is my opinion, and personal taste, and that's also a factor, and is different for everyone ....

[ugnaught]

The analog information is retained even after digitizing..... Several pixels can be considered as one analog state of change in luma signal, In other words the horizontal resolution is so low (about 200 changes in luma) which makes 704 is about 3 and a half times the native luma definition, So resizing to 640 won't affect the overall quality that much.

That just isn't reality at all. Sorry.

The ADC chip in the capture card doesn't retain the theoretical 320 horizontal as perfect little pixel groupings 2-3 pixels all with the same luma and chroma. It has already done its approximations and interpolation of the original analog signal and assigned wholly separate 720 pixels of horizontal resolution.

When you enact that avisynth script to do some form of spline resize it is working off of the 720 independently chroma'd and luma'd pixels that were approximations done by the ADC in the capture card.

Let's take a look, shall we?

Here is OP's original raw avi, and I've taken a single frame exported as a bitmap in virtualdub. Then using a single pixel grid we can zoom in.


[Attachment 55130 - Click to enlarge]


[Attachment 55131 - Click to enlarge]

THAT is what the spline resize is working with. It has no idea about the source material being "effectively" 320 lines of horizontal resolution. There are no leftover ghost traces of an analog signal. It is absolutely incapable of differentiating between a VHS source and a DVD source. There are no perfect groupings of 3 or so pixels all with the same luma and chroma to the point that "Several pixels can be considered as one analog state of change in luma signal".

Once a VHS has been captured digitally the old analog rules for the "effective resolution" of the image no longer apply. Period.

Now you could argue that the human eye can barely tell the different between 720 and 640 and so what is the big deal with resizing like that. Fair enough. But arguing that adding 60 pixels vertically is "disastrous" while trusting a script to take away 80 pixels horizontally is "ok" is a tough sell.

If OP captured at 640 X 480 then I wouldn't recommend stretching to 720 X 540. That adds nothing. But they aren't capturing at 640 X 480.


tldr, OP you did nothing wrong. Ignore these people telling you to crop to 640 X 480. They are working off of bad information leftover from the early 2000's.

[DB83]

Well there are real experts on here - I do not regard myself as one - and there are 'quacks'. Maybe I fit in to the latter but I still think I know more than you.


If I was to follow your logic then resizing a 4:3 dvd or 4:3 DV-avi to 720*540 would also be correct.


But do carry on and I will invite a real expert, if he does not see the topic prior, to comment.

[ugnaught]

If I was to follow your logic then resizing a 4:3 dvd or 4:3 DV-avi to 720*540 would also be correct.

Ideally every playback device and piece of software would respect the par of the 720x480 and display it as 4:3. But that just doesn't always happen 100% of the time.

Again, the 720x540 resize is just to maintain that aspect ratio for playback when the par is being ignored. It isn't required by any stretch of the imagination to make a video "correct".

All I am saying is that I would rather resize to 720x540 than 640x480 if this was my preservation project. Then I laid out reasons why.

Well there are real experts on here - I do not regard myself as one - and there are 'quacks'. Maybe I fit in to the latter but I still think I know more than you.

But do carry on and I will invite a real expert, if he does not see the topic prior, to comment.

That is kind of you to say.

Personally I think it just has more to do with the same bad information being spread around so much that it becomes "fact".

Regarding an expert, going to need somebody with the background in ADC chips that can explain how/why those chips interpolation techniques are able to add more details than what is seen in a 352x240(x2) vhs image. Then explain why we should proceed to ignore that additional detail and remove it by resizing down again.

Maybe somebody that worked at Analog Devices, Maxim or someplace similar.

I will contend I am not that level of an expert. But I can take a look at the output from the ADC chips and see that the horizontal resolution is not an effective 352 and that there are 720 independently colored pixels horizontally.

[dellsam34]

Analog VHS has more vertical information than horizontally and even if there is a capture card that can do 4000x3000 pixels it is still around 200x480 original information, you can go down to the pixel level as much as you want but the fact doesn't change that resizing vertically is a huge mistake unless it's done for specific purposes and always keep the original files.

And what's even more worse is doing this instead of the opposite of it:

All I am saying is that I would rather resize to 720x540 than 640x480 if this was my preservation project. Then I laid out reasons why

[DB83]

Just answer my remark about the dvd and the DV-avi. Only one of these has an inherent DAR but both are digitally represented at 720*480.


Look it up if you do not know and then convince me that 720*540 for both, or either, is acceptable.

[nbatapes]

Appreciate all of the replies to this thread...thank you!