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 <http://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?
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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