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_aspect_ratio >> 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_Size.html#2525 > > 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 > > > > > > > >
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