Problem with pixel aspect ratio of old Hi8 video

Hello,
my local video store digitalized some of my old Hi8 videos to mp4.
The Hi8 videos were 720*576 PAL and intended to be viewed on a good old 4:3 TV. As far as I remember, the pixel aspect ratio of these kind of videos was 4:3.

What I got from the store is a 720*576 mp4 file, and Davinci Studio tells me that it has square pixel size.
Here is my problem:
Whatever project settings or output settings I use in Davinci Studio, the result is always squeezed horizontally. Some results delivered even a approximately square video. I have no clue how to solve this issue. Any help is very appreciated. Thanks in advance,
Jens

What happens if you select the file in a bin on the Edit page, right click and choose Clip Attributes, and change the Pixel Aspect Ratio to another choice? I have had situations where there was a non-obvious setting here, and just through experimentation I found one that worked perfectly with the SD material I was working with.

A Google search revealed this discussion elsewhere, and you can see that the apparent pixel size of PAL is a little more complicated than you might think:

https://forum.videohelp.com/threads/364 ... or-768x576

Thanks for your help, very appreciated!
That's a good hint, I did not know this trick with the clip attributes. It helped a bit, but still (maybe, not sure) not ok.

I measured the size of the video in centimeters on my monitor when I open it in Windows 10 and calculated the ratio.
Here the results:

Original file I got from my dealer: 1,36
Davinci output without changing clip attributes: 1,19
Davinci output with clip attributes changed to "PAL": 1,28
Adobe Premiere output with PAL settings: 1,39

Project settings in Davinci:
Timeline resolution: 720x576 PAL
Pixel aspect ratio: 4:3 standard definition

Output settings in Davinci:
Resolution 720x576 PAL

btw: Adobe premiere recognizes the mp4 file which I got from my dealer as "720x576 (1,0940)".

I assume the problem comes from the weird aspect ratio of the file.

What I ask myself:
How did the file look like when I played it 20 years ago on my good old 4:3 TV? I do not remember. Because ther is some discrepancy:
4:3 = 1,33
720x576=1,25

In other words: Should I be satisfied with the 1,28 output from Davinci or are there further options to improve?
Regards,
Jens

If you already had a digital player at the time, it did the de-squeeze.

If you don't get the right PAR in the clip attributes, do your own by decoupling X and Y in the Inspector's zoom and go for 1,094 (as correctly seen by Adobe).

At the time of early digital TV, they tried to standardize at least one dimension, in this case X.
But that resulted in some mild squeeze for PAL and some stretch for NTSC.

Old SD formats don't use square pixels, so 720/576 is not your final aspect. This is why you have pixels aspect "correction" (on top of frame proportion). Notice that 720x576 is used for 4x3 as well as for 16x9, so with square pixels it would never work.

1.094 pixels aspect is correct, but only if you see 9 pixels on each side of black image. This comes from old analog era when not whole 720 lines were used for active image. It's actually:
702x576 + 9 pixels (sometimes also 704+ 8 pixels) on each side inactive lines (black for digital world).
702/576*1.094=1.3333 and this reflects an "old analog flagging".

In case of all 720 lines showing active image it's not so easy to tell if they are all really active or if it has been 702 stretched to all 720 line by someone else already.
For all 720 lines active you don't use 1.094 correction, but 1.0666, which is more precisely 16:15 correction (reflects more modern "digital flagging" for all 720 active lines).
Depending if you use an old CRT TV or modern one you may see 1 or another been correct. My own limited test (Pioneer KURO plasma+ Sony reference CRT) shown that for modern TV you should use "digital flagging" and forget about inactive lines from analog era. Difference is fairly small and you need to validate it on image with circle/squares (old CRT TVs quite often had problems with keeping aspect anyway, specially in corners).
It's all described here:
https://en.wikipedia.org/wiki/Pixel_aspect_ratio

It's quite often that files have no flagging (or wrong one), so you have to manually overwrite it in your NLE.

Resolve uses wrong flagging for SD exports, but at the end this is just metadata which can be ignored or honoured by different players. If your imported file is seen as 1:1 aspect then definitely overwrite it to 4x3 in clip attributes.

...
If you don't get the right PAR in the clip attributes, do your own by decoupling X and Y in the Inspector's zoom and go for 1,094 (as correctly seen by Adobe).
..

I tried that already. It looks correct in the preview (without that correction the preview has black bars left and right), but the height/width ratio of the resulting mp4 file only changes very slightly, this is still not enough.

Meanwhile, I found a workaround:
1) Change source clip attributes from "Square" to "PAL".
2) Change output settings from "720x576 PAL" to "custom, 768x576" and 4:3.

The output video (768x576, 4:3) has then the same height/width ratio as the source video which I got from my dealer (720x576, Square).

720x576 square pixels isn't any proper standard.
It may be fine if it has black bars, so someone inserted proper 4x3 into 720x576 frame (but then you just limit already low resolution further).
If you don't need it to be standard frame size (720x576) then making it custom size (with 4x3 aspect), but square pixels is some solution (not that bad actually taking into account that Resolve has bug for SD non-square exports).

Old SD formats don't use square pixels, so 720/576 is not your final aspect. This is why you have pixels aspect "correction" (on top of frame proportion). Notice that 720x576 is used for 4x3 as well as for 16x9, so with square pixels it would never work.

1.094 pixels aspect is correct, but only if you see 9 pixels on each side of black image. This comes from old analog era when not whole 720 lines were used for active image. It's actually:
702x576 + 9 pixels (sometimes also 704+ 8 pixels) on each side inactive lines (black for digital world).
702/576*1.094=1.3333 and this reflects an "old analog flagging".

In case of all 720 lines showing active image it's not so easy to tell if they are all really active or if it has been 702 stretched to all 720 line by someone else already.
For all 720 lines active you don't use 1.094 correction, but 1.0666, which is more precisely 16:15 correction (reflects more modern "digital flagging" for all 720 active lines).
Depending if you use an old CRT TV or modern one you may see 1 or another been correct. My own limited test (Pioneer KURO plasma+ Sony reference CRT) shown that for modern TV you should use "digital flagging" and forget about inactive lines from analog era. Difference is fairly small and you need to validate it on image with circle/squares (old CRT TVs quite often had problems with keeping aspect anyway, specially in corners).
It's all described here:
https://en.wikipedia.org/wiki/Pixel_aspect_ratio

It's quite often that files have no flagging (or wrong one), so you have to manually overwrite it in your NLE.

Resolve uses wrong flagging for SD exports, but at the end this is just metadata which can be ignored or honoured by different players. If your imported file is seen as 1:1 aspect then definitely overwrite it to 4x3 in clip attributes.

Thanks for your detailed explanation. In fact the clips I got from my dealer have a green frame on top and on both sides, but not at the bottom. See attached screenshot. The screenshot is 768x576, although the video is 720x576. Dont know why.

This looks like proper old fashion 4x3 analog video.
If you don't need to keep 720x576 frame (not delivering to TV station) then you can use square pixels aspect and any frame size (around original size) keeping 4x3 proportion (as you did). I would crop all crap ( which is typical for old analog content) around edges.