[Cin] Anamorphic 16:9 SD-DV(D) widescreen to AV1.webm

[Terje J. Hanssen]

Den 15.01.2024 17:03, skrev Andrea paz:
> A convenience when doing these tests is to apply the "Downsample"
> filter to the timeline track and set it, in H and W, to at least the
> value 40. This will immediately show whether the pixel shape is square
> or rectangular, and, in the latter case, whether it is stretched
> vertically or horizontally.
> There is also to mention the "Auto aspect ratio" option in Set Format.
> It always returns the pixel (PAR) to the square shape by changing the
> DAR. If you leave the Auto checked box, every time we make a change it
> is reset to the square pixel. Auto, however, turns off if you set one
> of the presets and you have to re-enable it manually.
> Crop or sometimes pad (letterbox) is unavoidable when we impose a
> different aspect ratio from the starting one.
> I'm running tests with Terje's sample (thanks!) and getting the same
> results as him.

> I honestly don't understand the difference in
> rendering between CinGG and ffmpeg. In Cingg the initial SAR (actually
> the PAR) goes from 4:3 (=1.333) to 64:45 (=1.422). However, 1,422 is
> the correct value (for CinGG), to see Raffaella Traniello's guide:
> http://www.g-raffa.eu/Cinelerra/HOWTO/anamorphic.html

Anamorphic 16/9 SD-DV(D)
DAR=16/9
When H=576 px, the width needs to be displayed horizontal (unsqeezed) 
with Wd=576x16/9=1024 px (square)
But the width needs to be stored (compressed, squeezed) within 
SD-DV(D)'s format Ws=720 px
SAR=Wd/Ws=(576x16/9)/720=64/45=1.4222
PAR=DAR/SAR=(16/9)/(64/45)=5/4=1.25

Conversion of anamorphic video into non-anamorphic video
http://www.miraizon.com/support/info_aspectratio.html
Pixel aspect ratios of common video formats
https://en.wikipedia.org/wiki/Pixel_aspect_ratio#Pixel_aspect_ratios_of_common_video_formats

> I still have to make a new build with Andrew's last 2 patches (for DV
> 16:9) to see if anything changes.