Den 12.01.2024 09:40, skrev Andrea paz:
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.
I have not much to add, but I think it would be useful to add a table with the actual DAR, SAR (and PAR?) values for the most common anamorphic video formats similar https://en.wikipedia.org/wiki/Pixel_aspect_ratio#Pixel_aspect_ratios_of_comm... And what and when is manual input necessary in Cinelerra Set Format beyoind Preset and possibly also in the Project setting?