Vhs capture advice.

[rgr]

The samples are very noisy, probably because the tapes and not (completely) fixed the VCR, but not completely unwatchable.

A simple AviSynth post-processing improves a bit. Just a quick attempt on my side, play with the parameters for better results.

sli image comparison: https://imgsli.com/MTU2MTI3

image comparison:
[Attachment 69271 - Click to enlarge]

video restored:
[Attachment 69272 - Click to enlarge]

video comparison:
[Attachment 69273 - Click to enlarge]

AviSynth script:

Where did you get this TemporalDegrain2 plugin? I tried this:
--> http://avisynth.nl/index.php/TemporalDegrain2
but i am getting an error:

Both clips should have the same colorspace!
(C:/Program Files (x86)lAviSynth+/pluginsG4+/TemporalDegrain-v2.6.4.avsi, line 441)
(C:/Program Files (x86)lAviSynth+/plugins64+/TemporalDegrain-v2.6.4.avsi, line 395)

[lollo]

Both clips should have the same colorspace!

That means you are mixing in the preview 2 clips with different color space (for example YV16 and YUY2).

The TemporalDegrain2 denoiser I use is a customized version of mine (the reasons are written at the beginning of the file). Here attached for you

[rgr]

Both clips should have the same colorspace!

That means you are mixing in the preview 2 clips with different color space (for example YV16 and YUY2).

The TemporalDegrain2 denoiser I use is a customized version of mine (the reasons are written at the beginning of the file). Here attached for you

But only one clip is sent to the plugin.
But I already found the cause -- reverting from 2.6.4 to 2.6.3 solves the problem.
I'll now check yours - thanks

[Sharc]

I’m sorry to keep asking what are probably stupid questions but its got confusing again.


So if i crop and resize with borders to 704x576, set SAR to 12:11

If I crop and and resize to square pixels, 1440x1080 or 960x720, set SAR to 1:1

Im not sure when to set SAR to 16:15, when I crop and resize to 720x576?

SAR 16:15 is for 720x576 videos that use the full frame (not a 704x576 portion) for the 4:3 DAR.

720 / 576 * 16 / 15 = 1.3333... = 4:3

@Leanoric: For what it's worth, here 3 .avi testclips which emulate the 3 cases. (I hope I did these correctly )
When your final encode shows the circle as an exact circle and the square as an exact square (within +/- 1 pixel) your encoding and playback is correct regarding aspect ratios.
File 2) emulates (approximates) the standard analog ITU capture case. The padding sidebars are just green instead of the usual black.

[Alwyn]

Like I said earlier, crop by any amount you want and set the Sample Aspect Ratio when you encode (12:11 for a PAL ITU cap, 16:15 for a full frame non-ITU PAL cap). Let the player/TV/graphics card do the resizing for you.

Thanks. I have finally realised that that technique doesn't produce a 720x576-sized file, but it does retain the correct geometry/ratio.

All this 12:11, 16:15 720x576 etc is doing my head in. I'm just going to stick with cropping in roughly 4:3 (eg 13 off the sides, 10 off the vertical) then resize to 768x576, SAR of 1:1 and be done with it.

As for circles, it is now clear to me there is no "standard" crop. Some videos need more cropping, some less, to retain the "circle", and without one, all you can do is guess that you've got the correct ratio. Perhaps 8 and 8 might be close to a "standard" crop, but it certainly isn't correct in man of my cases.

What intrigues me is why, for every other video format, we use square-pixel, but for SD we have all this anamorphic SAR/PAR/DAR nonsense. Fair enough that it was needed in the dark ages but now?

[Bwaak]

As for circles, it is now clear to me there is no "standard" crop. Some videos need more cropping, some less, to retain the "circle"

Cropping does not affect the circle shape (provided that the player honors pixel aspect ratio set in the video header), changing of pixel aspect ratio does.

See https://en.wikipedia.org/wiki/Pixel_aspect_ratio

What intrigues me is why, for every other video format, we use square-pixel

Not true. Tons of formats that do not use square pixels, like AVCHD, Blu-ray, HDV, XDCAM, HDCAM, DVCPROHD, various "HD-lite" broadcast, cable and satellite formats.

but for SD we have all this anamorphic SAR/PAR/DAR nonsense. Fair enough that it was needed in the dark ages but now?

Modern formats are built on this dark-ages format, which is not so old actually, only forty years old. It is the result of harmonizing digital versions of 625/50 and 525/60 formats and ensuring program exchange. Given certain number of lines and striving for the same sample rate, these are the numbers that resulted. EBU has several articles dedicated to the origins of Rec. 601.

You don't need to stick to these numbers. Many A/D converters allow you to sample directly into 640x480 or 768x576, so you don't need to resample if you want square pixels. Youtube uses square pixels as well.

[Eric-jan]

My guess is the conversion of an analog video signal has problems with the ratio of lines to pixel conversion, also different analog video settings per different brand device, makes the difference, at that time they thought the difference would be invisible due the overscan area of any tv, but with a capture of the complete signal, all is visible.
I notice this with recorded tv broadcasts, one sees more or less black areas at the sides, when switching in studio occurs.
I guess wheels of vehicles circles of clocks, or the universal (earth) logo are refferences to use indeed, otherwise preset aspect ratio settings in the editing software will help.
(analog will not be very exact anyway)

[Alwyn]

Back to the colour space change for HD (601 to 709). This is what I used in VDub 2:


[Attachment 69382 - Click to enlarge]

Result is attached (same file as before this edit, renamed). Is this a 709-compliant file? Mediainfo indicates so.

[Cornucopia]

709 is not appropriate for SD material. 601 is.


Scott

[Alwyn]

Scott, I miss-named that file, it is obviously HD and I know, as clearly indicated in my comment. I'm simply asking if the file is really a 709.

Edit: I've renamed the file attached in my previous post.

[Leanoric]

I’m sorry to keep asking what are probably stupid questions but its got confusing again.


So if i crop and resize with borders to 704x576, set SAR to 12:11

If I crop and and resize to square pixels, 1440x1080 or 960x720, set SAR to 1:1

Im not sure when to set SAR to 16:15, when I crop and resize to 720x576?

SAR 16:15 is for 720x576 videos that use the full frame (not a 704x576 portion) for the 4:3 DAR.

720 / 576 * 16 / 15 = 1.3333... = 4:3

@Leanoric: For what it's worth, here 3 .avi testclips which emulate the 3 cases. (I hope I did these correctly )
When your final encode shows the circle as an exact circle and the square as an exact square (within +/- 1 pixel) your encoding and playback is correct regarding aspect ratios.
File 2) emulates (approximates) the standard analog ITU capture case. The padding sidebars are just green instead of the usual black.

Thanks for that, I can see how the wrong SAR affects things now when its just a circle and square on the screen. I encoded an episode with the wrong SAR and couldnt really see that anything was off when watching it.

I think that for now to prevent any more **** ups, Im just going to stick to the same template each time. Crop to 692x560 and resize to 1440x1080, SAR 1:1. Hopefully I cant go wrong doing it that way.

That said, Ive been leaving the colour space selection with no change selected, should I be selecting rec 709? Im not planning on putting anything on youtube so maybe that doesnt matter?

[Sharc]

Crop to 692x560 and resize to 1440x1080, SAR 1:1. Hopefully I cant go wrong doing it that way.

You can practice this with my testclip 2) as well and check how close you get.

[Eric-jan]

What does "chroma location left" means ? never seen that before….

[Alwyn]

...

[jagabo]

What does "chroma location left" means ? never seen that before….

The location of the subsampled chroma: https://en.wikipedia.org/wiki/Chroma_subsampling#Sampling_positions

[Sharc]

As for circles, it is now clear to me there is no "standard" crop. Some videos need more cropping, some less, to retain the "circle", .....

You don't need a certain cropping to retain the circle. You can basically crop whatever you want (see attachment). Cropping doesn't geometrically distort the picture. The benefit of the SAR concept is that it preserves the objects geometry provided that the player reads and respects the SAR and you encode with the correct SAR. No resizing required, no worry about color space change. As has been said, in practice you have 2 choices for "4:3 PAL sources", namely SAR=16:15 or SAR=12:11. In the case of your clip it is 16:15.
Of course you must not force the playback to 4:3 for this cropped case, unless you pad the cropped frame accordingly.

[dellsam34]

Cropping doesn't geometrically distort the picture.

It does, Unless you build it up with black pixels back to 704x576, or crop to a resolution that has the equivalent ratio of 704:576 and resize to a square pixel resolution of a 4:3 ratio, which in this case the higher the better to avoid scaling artifacts. I used the word equivalent in purpose because honestly few pixels off give or take is not going to be noticeable.

[jagabo]

Cropping doesn't geometrically distort the picture.

It does

Cropping any amount and encoding with SAR flags does not distort the contents of the video. See the attached sample of your simulated ITU circle, cropped to 704x432 and encoded 12:11 SAR. You can crop by any amount and the circle will continue to be a circle, as long as you specify 12:11 SAR.

The only good reason to restore the cropped edges is if you're using a system that requires a standard frame size, like DVD and its 704x576 or 720x576 sizes.

[Alwyn]

I think I now have a handle on "SAR"s, although it still spins my head.

crop by any amount you want and set the Sample Aspect Ratio when you encode (12:11 for a PAL ITU cap, 16:15 for a full frame non-ITU PAL cap).

Referencing the above, how can I tell whether my capture is ITU, needing 16:15 or full ITU, needing 12:11? Sharc said my Lotto clip needs 16:15, but his circle/square clip needs 12:11.

It also makes editing in a video editor easier, as one doesn't have to crop each clip to prevent the edges jumping in and out as clips change. Processing one contiguous video such as an advert or movie is less of an issue because the edges won't change, but when you're putting together clips from various captures, the edges are going to be jumping about, even if padded to 704 0r 720.

Also, in my post 308 above, is the colour space of that file really 709? I'm trying to validate using VDub's colour space changer.

[Sharc]

Referencing the above, how can I tell whether my capture is ITU, needing 16:15 or full ITU, needing 12:11? Sharc said my Lotto clip needs 16:15, but his circle/square clip needs 12:11.

You would have to find an object of known shape in the video, like the circle in your example.
Open your video in an editor like VirtualDub for example. Leave it at its native stored frame size (means watch it at Sample Aspect Ratio 1:1 = square pixels; VirtualDub has a setting for this: Right click into the picture and select '1:1 pixels'). Now take a pixel ruler (google for one if you don't already have one) and measure the axes of the circle horizontally and vertically. In your example the horizonal axis of the circle is 266 pixels, and the vertical axis is 284 pixels. 284/266=1.068 which is very close to 16:15 = 1.067.

Do the same with my 12:11 examples 1) and 2) in post #304 and you will end up with ratios which are very close to 1.09. QED.

The problem is that it is often difficult to find a good circle in the video (ball, wheel, round clock filmed from the front). Then you will have to speculate. But when it is difficult to make up your mind, why bother? If you guessed wrong the error is ~2% only which very most people won't even notice.

[Sharc]

Cropping doesn't geometrically distort the picture.

It does, Unless you build it up with black pixels back to 704x576, or crop to a resolution that has the equivalent ratio of 704:576 and resize to a square pixel resolution of a 4:3 ratio, which in this case the higher the better to avoid scaling artifacts. I used the word equivalent in purpose because honestly few pixels off give or take is not going to be noticeable.

Cropping any amount and encoding with SAR flags does not distort the contents of the video.

Apologies, my bad, this was a misnomer. I wanted to say: "Cropping doesn't geometrically distort the shape of the objects in the picture".

For the sake of clarity (I hope) and to sum up (you know all this, of course):

Cropping changes the DAR (Display Aspect Ratio) of the picture (frame), resizing changes the SAR (Sample Aspect Ratio, aka PAR Pixel Asect Ratio) of the picture.

Take a piece of paper with outer dimensions of 4:3 for example. Draw exact squares and circles on it.

Cropping:
Take a scissors and cut the sheet, like 1 inch from left, 2 inches from top, whatever. The shape and dimensions of the squares and circles on the remaining sheet does not change. Squares are still squares, and circles are still circles. What has changed is the shape of the sheet. It is no longer 4:3, but somthing else according to your cutting. Means the DAR has changed, but not the shape of the objects.

Resizing:
Now imagine that the sheet is made of rubber. Stretch (or shrink) it horizontally and/or vertically and see how the shape of the objects (squares, circles) are affected: Squares are no longer squares but become rectangles; circles are no longer circles but have become ovals. Means the SAR (aka PAR) has changed. This distortion is called 'anamorphic', characterized by its SAR (aka PAR). All DVDs (at least I know of), 4:3 or 16:9 DAR, of PAL or NTSC origin, are anamorphic. Same for analog captures.

When playing back such material one has to reverse the anamorphic distortion, either by resizing to square pixels or informing the player about the SAR so it can do the resizing itself on the fly.

One can easily practice this with the 3 examples of post #304.

[dellsam34]

Cropping any amount and encoding with SAR flags does not distort the contents of the video. See the attached sample of your simulated ITU circle, cropped to 704x432 and encoded 12:11 SAR. You can crop by any amount and the circle will continue to be a circle, as long as you specify 12:11 SAR.

As long as the proportions are right within few pixels from 704:576, Try to crop to 200x576, or 704x350 and see what you end up with, That's my point.

Edit: Unless you mean you customize the SAR according to the cropped resolution then that's a different story, but if you use standard SAR for 720 and 704 then that's not going to work.

[dellsam34]

Cropping:
Take a scissors and cut the sheet, like 1 inch from left, 2 inches from top, whatever. The shape and dimensions of the squares and circles on the remaining sheet does not change. Squares are still squares, and circles are still circles. What has changed is the shape of the sheet. It is no longer 4:3, but somthing else according to your cutting. Means the DAR has changed, but not the shape of the objects.

No, If you don't pad it back to 704x576 it will change the geometry of the picture, because whatever resolution left from the cropping will fill the 4:3 frame and it will be distorted. Read post #317 again.

[Sharc]

Cropping:
Take a scissors and cut the sheet, like 1 inch from left, 2 inches from top, whatever. The shape and dimensions of the squares and circles on the remaining sheet does not change. Squares are still squares, and circles are still circles. What has changed is the shape of the sheet. It is no longer 4:3, but somthing else according to your cutting. Means the DAR has changed, but not the shape of the objects.

No, If you don't pad back to 704x576 it will change the geometry of the picture, because whatever resolution left from the cropping will fill the 4:3 frame and it will be distorted.

Distorted only if you are forcing the player (TV, whatever) to play the cropped video as 4:3. If the player respects the SAR flag one will see the cropped picture (at its new DAR which is no longer 4:3 of course) with the objects undistorted. If the player respects the SAR there is actually no need for padding back. Of course one can pad it back in order to get the same output irrespective of playing it as 4:3 or according to the SAR. Double stitched, so to speak. Read posts #298 and #318 again

[Alwyn]

No, If you don't pad it back to 704x576 it will change the geometry of the picture, because whatever resolution left from the cropping will fill the 4:3 frame and it will be distorted.

No, that's not correct as I finally understand. When you crop, you just end up with an odd-ball resolution video which is otherwise correctly proportioned. Here's one viciously cropped, not resized or padded, and encoded with a SAR of 16:15. Note round engine. The original was a 720x576, 4:3 video.

You have to let VLC Player use "default" as the zoom. If you force it to 4:3, it stretches wide badly. Interestingly, despite it's weird dimensions, it plays correctly in ios.

[Sharc]

@Alwyn: You got it!
All these things are just a bit difficult to explain properly in words, or sometimes fighting words, in addition to foreign language issues, I am afraid.
I think these discussions will resurrect as long as this forum will exist. A Zombie, sort of.

[Alwyn]

Thanks for your explanations, Sharc and Jagabo.

I have come across a few videos that, for whatever reason, don't look right eg fattish heads (without circles), and in those cases, it seems to me that cropping and checking with a pseudo 4:3 display eg VDub right-click display option is the only way to get the proportions the way you want them. It's then a case of cropping off the top and bottom in the correct 4:3 ratio, then resizing to 768x576 and encoding with SAR 1:1.

Attached is an example. The gunsight is round, but in the video, even at 4:3, it's not.

[dellsam34]

No, that's not correct as I finally understand. When you crop, you just end up with an odd-ball resolution

That's why you can't crop to any resolution, You are contradicting yourself. Cropping is optional to remove junk, but you cannot crop freely from each side, it has to follow the 704x576 rule, As I said above try to crop to say 200x576 and show me how that doesn't change the geometry, I don't even know why we are arguing this in 2023 when the standard was set in the 80's.

[dellsam34]

Distorted only if you are forcing the player (TV, whatever) to play the cropped video as 4:3. If the player respects the SAR flag one will see the cropped picture (at its new DAR which is no longer 4:3 of course) with the objects undistorted. If the player respects the SAR there is actually no need for padding back. Of course one can pad it back in order to get the same output irrespective of playing it as 4:3 or according to the SAR. Double stitched, so to speak. Read posts #298 and #318 again

Sure if you only want to watch on the computer screen in an oddball frame, TV's and monitors can only show 4:3 materials as 4:3 frame and all the setting has to match that frame. For your own viewing pleasure you can do whatever you please but to share with the rest of the world you have to follow the standard.

[Alwyn]

As I said above try to crop to say 200x576 and show me how that doesn't change the geometry,

Look at the SAAA video. I did crop it to 266x576. It's nothing like 720x576, it has no padding, but the engine is still round, like it should be.