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<div class="moz-cite-prefix">Den 08.01.2024 01:39, skrev Andrew
Randrianasulu:<br>
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cite="mid:CA+rFky5WZzaQm_rVx5vkgdaVt4MQv+mxLWyx1+mC4a+r-pa3wA@mail.gmail.com">
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<div dir="ltr" class="gmail_attr">пн, 8 янв. 2024 г., 01:52
Terje J. Hanssen <<a
href="mailto:terjejhanssen@gmail.com"
moz-do-not-send="true" class="moz-txt-link-freetext">terjejhanssen@gmail.com</a>>:<br>
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<div>Den 07.01.2024 23:35, skrev Andrew Randrianasulu:<br>
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<div dir="ltr" class="gmail_attr">пн, 8 янв.
2024 г., 01:31 Andrea paz <<a
href="mailto:gamberucci.andrea@gmail.com"
target="_blank" rel="noreferrer"
moz-do-not-send="true"
class="moz-txt-link-freetext">gamberucci.andrea@gmail.com</a>>:<br>
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<blockquote class="gmail_quote"
style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I
don't quite understand how ffmpeg considers
the various aspect<br>
ratios. However from the site lurkertech you
pointed to (and from<br>
which I had taken some definitions put in the
manual) PAR and SAR are<br>
not the same thing: PAR is about pixel shape
and size; SAR is about<br>
frame shape and size.<br>
<br>
To change the manual I would like to be sure
that ffmpeg really<br>
considers PAR=SAR.<br>
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<div dir="auto">lets wait until ffmpeg-users reply
to just send email :)</div>
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<br>
The wikipedia article section "Confusion with display
aspect ratio" points out:<br>
<a
href="https://en.wikipedia.org/wiki/Pixel_aspect_ratio#Confusion_with_display_aspect_ratio"
target="_blank" rel="noreferrer"
moz-do-not-send="true" class="moz-txt-link-freetext">https://en.wikipedia.org/wiki/Pixel_aspect_ratio#Confusion_with_display_aspect_ratio</a><br>
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: <i>storage aspect ratio</i> (<i>SAR</i>)
and <i><a
href="https://en.wikipedia.org/wiki/Display_aspect_ratio"
title="Display aspect ratio" target="_blank"
rel="noreferrer" moz-do-not-send="true">display
aspect ratio</a></i> (abbreviated <i>DAR</i>, also
known as <i><a
href="https://en.wikipedia.org/wiki/Image_aspect_ratio"
title="Image aspect ratio" target="_blank"
rel="noreferrer" moz-do-not-send="true">image aspect
ratio</a></i> and <i><a
href="https://en.wikipedia.org/wiki/Picture_aspect_ratio"
title="Picture aspect ratio" target="_blank"
rel="noreferrer" moz-do-not-send="true">picture
aspect ratio</a></i>). Also, <i>pixel aspect ratio</i>
(<i>PAR</i>) is also known as <i>sample aspect ratio</i>
(abbreviated <i>SAR</i>) in some industrial standards
(such as <a
href="https://en.wikipedia.org/wiki/Advanced_Video_Coding"
title="Advanced Video Coding" target="_blank"
rel="noreferrer" moz-do-not-send="true">H.264</a><sup
id="m_-345566080737687439cite_ref-2"><a
href="https://en.wikipedia.org/wiki/Pixel_aspect_ratio#cite_note-2"
target="_blank" rel="noreferrer"
moz-do-not-send="true">[2]</a></sup>) and output of
programs (such as <i><a
href="https://en.wikipedia.org/wiki/Ffmpeg"
title="Ffmpeg" target="_blank" rel="noreferrer"
moz-do-not-send="true">ffmpeg</a></i><sup
id="m_-345566080737687439cite_ref-3"><a
href="https://en.wikipedia.org/wiki/Pixel_aspect_ratio#cite_note-3"
target="_blank" rel="noreferrer"
moz-do-not-send="true">[3]</a></sup>). Note the
reuse of the abbreviations <i>PAR</i> and <i>SAR</i>.
This article uses only the terms pixel aspect ratio,
display aspect ratio and storage aspect ratio to avoid
ambiguity.<br>
<br>
And in Note 3<br>
<span><cite><a rel="nofollow noreferrer"
href="https://trac.ffmpeg.org/ticket/1776"
target="_blank" moz-do-not-send="true">"ffprobe
shows PAR as SAR"</a>. <a
href="http://ffmpeg.org" target="_blank"
rel="noreferrer" moz-do-not-send="true">ffmpeg.org</a><span>.
Retrieved <span>2022-06-10</span></span>.<br>
<a href="https://trac.ffmpeg.org/ticket/1776"
target="_blank" rel="noreferrer"
moz-do-not-send="true"
class="moz-txt-link-freetext">https://trac.ffmpeg.org/ticket/1776</a></cite></span></div>
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<div dir="auto">well, both cingg and ffmpeg can interface with
digitizing boards, but after another pass at reading</div>
<div dir="auto"><br>
</div>
<div dir="auto"><a
href="https://lurkertech.com/lg/video-systems/#sqnonsq"
moz-do-not-send="true" class="moz-txt-link-freetext">https://lurkertech.com/lg/video-systems/#sqnonsq</a><br>
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<div dir="auto"><br>
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<div dir="auto">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.</div>
<div dir="auto"><br>
</div>
<div dir="auto">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.</div>
<div dir="auto"><br>
</div>
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Hm, yet another definition; "Picture Aspect Ratio" used.<br>
<cite><br>
<br>
However, the CinGG manual seemingly uses this
Pixel-Display-Storage Aspect Ratio definitions:<br>
<a class="moz-txt-link-freetext" href="https://cinelerra-gg.org/download/CinelerraGG_Manual/Temporary_Track_Output_Size.html#2525">https://cinelerra-gg.org/download/CinelerraGG_Manual/Temporary_Track_Output_Size.html#2525</a><br>
</cite>
<p>
In <span class="texttt">Settings <span class="MATH">→</span>
Format</span> 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:
</p>
<p> <span class="MATH"><i>PAR</i> = DAR/SAR</span></p>
<span class="MATH">Is it correct that Canvas size "W Ratio" and "H
Ratio" define PAR, while "Aspect Ratio" defines DAR in the
Settings > Format widget?<br>
<br>
But there is something confusing I don't understand (possibly
wrong) with the Presets values as far as I can see:<br>
</span>
<ul>
<li><span class="MATH">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</span></li>
<li><span class="MATH">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</span></li>
</ul>
<span class="MATH">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?<br>
The second HDV w/DAR=16:9 (anamorphic squeezed), should seemingly
instead have PAR 4:3, that is </span><span class="MATH">W
Ratio=1.3333, H Ratio=1.0000?</span><br>
<span class="MATH"><br>
Else the PAL SD-DV(D) is seemingly ok<br>
</span>
<ul>
<li><span class="MATH">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</span></li>
</ul>
<span class="MATH"> <br>
</span>
<p><span class="MATH"><br>
</span>
</p>
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