Yet another one confused with SAR, PAR, DAR and cropping

[JollyDin]

IMO

That capture is unnatural/unexpected. SD captures should need to be displayed at 768x576; if you do that with that file, it's stretched (use VDub, right-click on the video, look at 1:1 and then 4:3). With yours, at 720x576 1:1, it shows a circle.

I would expect a capture to, at 1:1, look laterally squashed. You then apply the 12:11 (or manual crop and resize to 768x576) so that it stretches to the correct, circular shape. See Sharc's post #2.

I suspect your capture/conversion chain has introduced aspect ratio errors.

Attached, a "proper" analogue capture of a wheel. Do your two exports on that wheel: you'll see the effects have reversed: exporting at SAR 1:1 results in a squashed wheel and exporting SAR at 12:11 results in a correct, circular wheel.

Thank you Alwyn for checking.

OK I opened your Wheel avi on Vdub and indeed looks squashed and on export at SAR=12:11 it looks correct and circular.
I think I am now getting it.

I think you gave the answer to your issue in your post #9 yourself: It's your setup. Your Laptop player applied the SAR stretching to the source file and outputs a "SAR 1:1 equivalent" analog video at its S-video output. So when you capture this and encode it with SAR 12:11 the conversion is applied twice, so it gets horizontally stretched (~9%) upon playback via a player which respects the SAR signalling.
This is what I had in mind in post#16 with the "... silent resizing under the hood". It's your setup which caused all the confusion, IMO.
Your Laptop player isn't emulating a VCR correctly. It processes the source.

Thank you Sharc.
OK I got to admit sending S-Video output from a laptop is not the same as a video device (Camcorder, VHS, etc) and looks like it may not be following a standard.

So I just filmed a circle (a lid) on my Sony TRV-320E camcorder, played it back while capturing.
The circle is indeed "squashed" :


[Attachment 89609 - Click to enlarge]

Interestingly, in VDub, right-clicking the original video pane shows "Free Adjust" as the aspect ratio (instead of "1:1 pixel (Square)"):


[Attachment 89610 - Click to enlarge]
Then clicking on "1:1 Pixel (Square)" it still shows squashed and then clicking on "4:3 frame (TV)" it is indeed displayed as a correct circle.
My captured clip of the lid is attached (test-cam-1.avi) together with the exported as SAR-12:11.

So does that mean my capture setup (VD2 on Win10 with Matrox MX02) is working correctly ?

Also attached in another capture (Test-huff-06.avi) captured the same way.
This was recorded on a Video8 camcorder (now dead) but played back on the Sony TRV-320E and captured with my setup

Does this look correct ?

[Sharc]

Yes, correct. All 3 files have a SAR of 12:11
For the the .mp4 the circle is displayed correctly provided your player respects the SAR (stretching the picture by 1.0909...)
If your player/TV ignores the SAR you have to configure the player/TV to play it forced as 4:3 (a player setting option).

Alternatively for the 720x576 .avi you can crop 16 pixel in total from the width (gives a frame of 704x576) and resize it to any 4:3 ratio like 768x576 or 1440x1080, means resizing it to square pixels - and encode it with SAR 1:1. Or crop it and force the player to play the cropped 704x576 .avi as 4:3. (The .avi has no provision for SAR signalling, so the player has to be configured to play the 704x576 as 4:3).

Interestingly, in VDub, right-clicking the original video pane shows "Free Adjust" as the aspect ratio (instead of "1:1 pixel (Square)")

Set the tickmark to 1:1 pixels. "Free Adjust" means you can stretch and shrink that window freely in any direction as you like - for experimenting.

[JollyDin]

Yes, correct. All 3 files have a SAR of 12:11
For the the .mp4 the circle is displayed correctly provided your player respects the SAR (stretching the picture by 1.0909...)
If your player/TV ignores the SAR you have to configure the player/TV to play it forced as 4:3 (a player setting option)

Thank you !

OMG..all this time I been playing back captured files in HUFFYUV and always had a nagging feeling that it did not look right and even making cardinal sin of exporting them with SAR=1:1 :facepalm:

Now I get it !

Now the other thing I need to figure out is the cropping...or rather resizing WITHOUT padding.
Many seem to think this is no no as it introduces other issues like artifacts, distortions, etc.

Even though the black padding areas are small, when displayed on a TV, the borders at the Top and Bottom are visible (i.e. the picture does not go all way to top/bottom edges of the screen). The black bars at the sides are so wide (relatively to the padding) that they drown out the padding so they are not as distracting.

Is there a "recipe" for cropping out the overscans and video head flyback at the top/bottom and effectively resize so that 4:3 is still preserved and SAR=12:11 ?

[Sharc]

If you encode with SAR 12:11 and your player respects it you can crop the picture as you like to any dimensions (mod2). You won't need any padding. That's the beauty of the correct SAR signalling/encoding. Of course the cropped picture won't be 4:3 anymore after "random" cropping, but the objects will remain undistorted. The elegance of the correct SAR application!
Very most TV's will add black borders automatically as needed to fit within its "canvas" (usually 16:9).
Try it. Crop your captures as you prefer (e.g. for removing side borders and top and bottom crud, or only keeping a portion of the picture ... whatever), then encode with SAR 12:11 and play it (assuming your player respects the SAR). The objects in the cropped picture will remain undistorted which is what really matters, rather than some exact 4:3.
Example attached, cropped 18 left, 136 top, 24 right, 40 bottom.

Added:
In case of upscaling take care not to violate the SAR, means upscale width and hight in proportion (zooming). Otherwise you change the SAR and you need to calculate the new SAR and encode with this new SAR to preserve the objects shape.

[jagabo]

Crop as much as you like, then encode with 12:11 SAR. Any player that responds to the SAR will play it with the correct aspect ratio and will fill either the width or height of the screen with the picture.

[JollyDin]

If you encode with SAR 12:11 and your player respects it you can crop the picture as you like to any dimensions (mod2). You won't need any padding. That's the beauty of the correct SAR signalling/encoding. Of course the cropped picture won't be 4:3 anymore after "random" cropping, but the objects will remain undistorted. The elegance of the correct SAR application!
Very most TV's will add black borders automatically as needed to fit within its "canvas" (usually 16:9).
Try it. Crop your captures as you prefer (e.g. for removing side borders and top and bottom crud, or only keeping a portion of the picture ... whatever), then encode with SAR 12:11 and play it (assuming your player respects the SAR). The objects in the cropped picture will remain undistorted which is what really matters, rather than some exact 4:3.
Example attached, cropped 18 left, 136 top, 24 right, 40 bottom.

Added:
In case of upscaling take care not to violate the SAR, means upscale width and hight in proportion (zooming). Otherwise you change the SAR and you need to calculate the new SAR and encode with this new SAR to preserve the objects shape.

Love it !
Just tried that and worked perfectly. The key is to watch the proportions if upscaling.
Loaded the videos onto my Emby Server and the Emby player on the TV plays the cropped/zoomed files perfectly and the lid is perfectly round.
I did the same with Alwyn's Wheel and it played perfectly.

Definitely get it now.

Many thanks

[JollyDin]

Crop as much as you like, then encode with 12:11 SAR. Any player that responds to the SAR will play it with the correct aspect ratio and will fill either the width or height of the screen with the picture.

Got it.
many thanks for all your tips.
no doubt I'll be back for more help

[JollyDin]

So what I learnt was :

• that the PAL SD captured files look "squashed" but are correct as they are ment to be and nothing to worry about.
• exporting 4:3 video with SAR=12:11 "stretches" it back to the correct undistorted ratio.
• crop and resize as much as you like but match the SAR ratio in proportion

No doubt that on this huge forum, what I learned is documented somewhere but did not find it easily in three bullet points.
I'll make this thread a sticky for myself and point others to it.

Thank you all for learnings

[Alwyn]

crop and resize as much as you like but match the SAR ratio in proportion

Not quite.

If you set the SAR on export eg 12:11, there is no need to crop in any particular proportion. The file will be encoded to display correctly ie wheels will be round wheel regardless of what cropping has been done. Provided the player respects the SAR, the only way you'll notice is the sides will probably not be at the normal 4:3 position. For example, you may end up with a square-looking frame but the wheel will still be round.

If you particularly want a FAR (frame shape) of 4:3, eg 768x576, 1440x1080 then you need to first, crop off the 2 x 8 pixels, then do another crop in the 4:3 ratio as required, say 8 pixels off the sides, 6 pixels off the vertical. Crop in multiples of 2. Then resize to a 4:3 frame using SAR of 1:1.

And deinterlace before you do any vertical cropping so you don't mess up the field order.

[Sharc]

If you particularly want a FAR (frame shape) of 4:3, eg 768x576, 1440x1080 then you need to first, crop off the 2 x 8 pixels, then do another crop in the 4:3 ratio as required, say 8 pixels off the sides, 6 pixels off the vertical. Crop in multiples of 2. Then resize to a 4:3 frame using SAR of 1:1.

Sidenote: ~yes - to be more exact crop 18 pixels in total (left+right, mod2 each) rather than blindly symmetrical 2x8, depending how the active 702x576 PAL picture is horizontally centered in the 720x576 captured frame.
But as said before - provided the player reads the SAR - there is no need to take the more complicated detour via resizing to square pixels and have the picture cropped and scaled in several steps to get it eventually displayed correctly on the TV screen.
These days there is hardly a good reason to scale and display "nominal 4:3" to exact 4:3 (DAR and FAR) IMO as 4:3 screens have disappeared since a while.
Anyway, I think the OP got all this right now.....