Andrea, an explanation in the manual would be a good addition. I have read what you wrote and studied a little of what I could find online, and am still somewhat confused so am unable to determine if your explanation sounds correct. But it seems to fit. ...Phyllis
On Fri, Jan 12, 2024 at 1:40 AM Andrea paz via Cin < [email protected]> wrote: > > 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. > -- > Cin mailing list > [email protected] > https://lists.cinelerra-gg.org/mailman/listinfo/cin >
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