пн, 8 янв. 2024 г., 13:42 Terje J. Hanssen <[email protected]>:
Den 08.01.2024 01:39, skrev Andrew Randrianasulu:
пн, 8 янв. 2024 г., 01:52 Terje J. Hanssen <[email protected]>:
Den 07.01.2024 23:35, skrev Andrew Randrianasulu:
пн, 8 янв. 2024 г., 01:31 Andrea paz <[email protected]>:
I don't quite understand how ffmpeg considers the various aspect ratios. However from the site lurkertech you pointed to (and from which I had taken some definitions put in the manual) PAR and SAR are not the same thing: PAR is about pixel shape and size; SAR is about frame shape and size.
To change the manual I would like to be sure that ffmpeg really considers PAR=SAR.
lets wait until ffmpeg-users reply to just send email :)
The wikipedia article section "Confusion with display aspect ratio" points out:
https://en.wikipedia.org/wiki/Pixel_aspect_ratio#Confusion_with_display_aspe... Pixel aspect ratio is often confused with different types of image aspect ratios; the ratio of the image width and height. Due to non-squareness of pixels in Standard-definition TV, there are two types of such aspect ratios: *storage aspect ratio* (*SAR*) and *display aspect ratio <https://en.wikipedia.org/wiki/Display_aspect_ratio>* (abbreviated *DAR*, also known as *image aspect ratio <https://en.wikipedia.org/wiki/Image_aspect_ratio>* and *picture aspect ratio <https://en.wikipedia.org/wiki/Picture_aspect_ratio>*). Also, *pixel aspect ratio* (*PAR*) is also known as *sample aspect ratio* (abbreviated *SAR*) in some industrial standards (such as H.264 <https://en.wikipedia.org/wiki/Advanced_Video_Coding>[2] <https://en.wikipedia.org/wiki/Pixel_aspect_ratio#cite_note-2>) and output of programs (such as *ffmpeg <https://en.wikipedia.org/wiki/Ffmpeg>*[3] <https://en.wikipedia.org/wiki/Pixel_aspect_ratio#cite_note-3>). Note the reuse of the abbreviations *PAR* and *SAR*. This article uses only the terms pixel aspect ratio, display aspect ratio and storage aspect ratio to avoid ambiguity.
And in Note 3 "ffprobe shows PAR as SAR" <https://trac.ffmpeg.org/ticket/1776>. ffmpeg.org. Retrieved 2022-06-10. https://trac.ffmpeg.org/ticket/1776
well, both cingg and ffmpeg can interface with digitizing boards, but after another pass at reading
https://lurkertech.com/lg/video-systems/#sqnonsq
I hopefully hope that only DEVICE DRIVERS for analog input cards must deal with picture aspect ratio, as they deal with sampling of analog video.
One can also hope that modern smartphone cameras also follow square pixels convention, because they typically do not send video over SDI but hand it into system-on-chip shared memory where encoder/display blocks deal with it directly.
Hm, yet another definition; "Picture Aspect Ratio" used.
However, the CinGG manual seemingly uses this Pixel-Display-Storage Aspect Ratio definitions:
https://cinelerra-gg.org/download/CinelerraGG_Manual/Temporary_Track_Output_...
In Settings → Format there is the additional possibility to vary the shape of the pixels from 1:1 (square) to handle anamorphic formats. In such cases we use:
*PAR* = DAR/SAR Is it correct that Canvas size "W Ratio" and "H Ratio" define PAR, while "Aspect Ratio" defines DAR in the Settings > Format widget?
But there is something confusing I don't understand (possibly wrong) with the Presets values as far as I can see:
- Preset 1080i/25 set: Canvas size Width=1920, Height=1080, W Ratio=1.3333, H Ratio=1.0000 and Aspect ratio=16.0000:9.0000 - Preset HDV 1080i/25 set: Canvas size Width=1440, Height=1080, W Ratio=1.0000, H Ratio=1.0000 and Aspect ratio=16.0000:9.0000
The first is obviously FHD w/DAR=16:9 out of the frame size 1920x1080. If so, shouldn't PAR be 1:1, that is W Ratio=1.000 and H Ratio=1.000? The second HDV w/DAR=16:9 (anamorphic squeezed), should seemingly instead have PAR 4:3, that is W Ratio=1.3333, H Ratio=1.0000?
well, this is *very possible* that I mixed them all wrong way! It really advisable to try and get at least main source code downloaded to you linux machine,Terje. Even if build attempt fails out we *eventually* will come to something working, so it will be easier for you to see how changes affect display/editing of real media.
Else the PAL SD-DV(D) is seemingly ok
- Preset PAL 576i -DV(D) set: Canvas size Width= 720, Height=576, W Ratio=0.5000, H Ratio=0.5333 and Aspect ratio=4.0000:3.0000