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

Andrea paz gamberucci.andrea at gmail.com
Fri Jan 12 09:40:15 CET 2024

> Also, pixel aspect ratio (PAR) is also known as sample aspect ratio (abbreviated SAR) in some industrial standards (such as H.264[2]) and output of programs (such as ffmpeg
> Note 3: "ffprobe shows PAR as SAR". ffmpeg.org. Retrieved 2022-06-10.

Yes, exactly. That is what confuses me.
The theory is simple: DAR = PAR x SAR
DAR and SAR are "frame aspect ratio," PAR is "pixel aspect ratio." It
can be said that when SAR (let's imagine it as Width x Height pixels,
although it can be expressed as a ratio) is different from DAR we have
an anamorphic video and on the Compositor we see the deformed image.
Then we intervene with PAR which enlarges or shrinks the pixel so that
SAR is equal to DAR again.
A possible first confusion is that SAR and DAR can be expressed as
both Width x Height and aspect ratio. Another thing that can be
confusing is that SAR is not about the Set Format window, but only
about the Resource --> Assett --> Info --> Resize, or also Timeline
--> RMB --> Resize Track or, further, the Scale plugin).

I don't quite understand why ffmpeg and CinGG confuse the definitions
of PAR and SAR. Maybe for simplicity of code? In fact, the CinGG
workflow is not difficult: we choose the project properties, including
the frame size with the "Aspect ratio" option of the Set Format window
(which is tied to Width x Height). Then, depending on the sources, we
can change W and H, using W Ratio and H Ratio to perform the
calculations automatically. All without the need to recall the
concepts of SAR, PAR and DAR. If we then consider that anamorphic
pixels affect only a very small minority of cases, not putting the
concept of PAR serves to consider W/H Ratio as just a simple
multiplicative factor between the initial and project frame sizes.

Does this explanation sound correct to you? I would appreciate your
opinions, because I would like to change the manual.

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