Re: [FFmpeg-user] Glossary: DAR, PAR, and SAR

[Nicolas George]

Mark Filipak (ffmpeg) (12020-09-30):
> Revision: Shorter sentences, better consistency, no extra 'lesson' about how 
> to minimize ratios.\
> Formatted for email, plain text.

What is you purpose in writing this?

If you intend to make a generic erudite glossary for all video terms,
then the mailing-list for using FFmpeg is not the place to do it.

If you intend to make a glossary useful for FFmpeg users, then get rid
of all the useless lint about obsolescent standards (H.262? seriously?)
and irrelevant terms. In particular:

> PAR (picture aspect ratio [1]) [noun]: 1, The horizontal-to-vertical
>   size [3] ratio (H:V, e.g. 5:4, 3:2) for pictures. PAR is

get rid of this one altogether, because nothing in FFmpeg use it, and
rightly, because nobody should use it.

-- 
  Nicolas George


signature.asc
Description: PGP signature
___
ffmpeg-user mailing list
ffmpeg-user@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-user

To unsubscribe, visit link above, or email
ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".

Re: [FFmpeg-user] Glossary: DAR, PAR, and SAR

[Mark Filipak (ffmpeg)]

Revision: Shorter sentences, better consistency, no extra 'lesson' about how to 
minimize ratios.\
Formatted for email, plain text.

DAR (display aspect ratio [1]) [noun]: 1, The width-to-height ratio
  (W:H, e.g. 16:9, 4:3) for the intended display. DAR is distingushed
  by metadata: 'aspect_ratio_information', (also see "SAR", note [2]).
  2, H.262 §3.44: "The ratio of height divided by width (in spatial
  measurement units such as centimetres) of the intended display."
  [2].
  [1] It's mistakenly asserted by some that "DAR" is an acronym for
  "data aspect ratio" or "disc aspect ratio".
  [2] Criticism: H.262 claims that DAR is a "ratio", then wrongly
  defines it as a quotient (which it turns upside down): "height
  divided by width"; also H.262 §6.3.3 (i.e. "3 ÷ 4", "9 ÷ 16").

PAR (picture aspect ratio [1]) [noun]: 1, The horizontal-to-vertical
  size [3] ratio (H:V, e.g. 5:4, 3:2) for pictures. PAR is
  distingushed by metadata: 'horizontal_size' & 'vertical_size', [2]
  [4] (also see "SAR", note [2]).
  [1] It's mistakenly asserted by some that "PAR" is an acronym for
  "pixel aspect ratio".
  [2] PAR can also be calculated from DAR & SAR thusly: PAR = DAR/SAR.
  [3] Note that PAR is virtual (i.e. defined by dataset indexes, not
  by physical dimensions).
  [4] Criticism: H.262 doesn't define PAR, however, it does define a
  quotent that correlates with PAR, to wit: H.262 §6.3.3,
  aspect_ratio_information:
"SAR = DAR × horizontal_size/vertical_size".
  The foregoing implies that H.262 would have defined PAR as
  vertical_size/horizontal_size. Opinion: By defining DAR & SAR as
  quotients (which it turns upside down), and by implying that
  metadata: 'aspect_ratio_information', is also such a quotient
  (which it also turns upside down), H.262 causes much confusion
  that helps explain why so many Internet sites get DAR, PAR, and
  SAR wrong.

SAR (sample aspect ratio [1]) [noun]: 1, The physical horizontal-to-
  vertical spacing ratio (H:V) for samples [2][3]. SAR is
  distinguished as a computed value: DAR/SAR. 2, H.262 §3.114: "This
  specifies the relative distance between samples. It is defined (for
  the purposes of Rec. ITU-T H.262 | ISO/IEC 13818-2), as the vertical
  displacement of the lines of luminance samples in a frame divided by
  the horizontal displacement of the luminance samples [2]. Thus, its
  units are (metres per line) ÷ (metres per sample)." [7].
  [1] It's mistakenly asserted by some that "SAR" is an acronym for
  "storage aspect ratio".
  [2] A standardized set of picture sizes & aspects has been
  established:
 display DAR picture PARSAR = DAR/PAR
   16:9-2160:  3840 x 2160  16:9 : 3840 x 2160  16:9 :  1:1
4:3-2160:  2880 x 2160   4:3 : 2880 x 2160   4:3 :  1:1
   16:9-1080:  1920 x 1080  16:9 : 1920 x 1080  16:9 :  1:1
4:3-1080:  1440 x 1080   4:3 : 1440 x 1080   4:3 :  1:1
   16:9-576:   1024 x 576   16:9 :  720 x 5765:4 : 64:45
4:3-576:768 x 5764:3 :  720 x 5765:4 : 16:15
   16:9-480:853 x 480   16:9 :  720 x 4803:2 : 32:27
4:3-480:640 x 4804:3 :  720 x 4803:2 :  8:9  [4]
  [3] Ideally, SAR would also be the width-to-height ratio of the
  sampling aperture, but that is not mandatory.
  [4] Example: If a 35mm film area (0.906 x 0.680 inches) is to
  produce 345,600 samples (visual density) with 480 rows (vertical
  resolution), then each row must have 720 samples (horizontal
  resolution) [5] and sample spacing should be 32 µm horizontally
  by 36 µm vertically [6].
  [5] (345,600 samples)/(480 rows).
  [6] (0.906 in)(25400 µm/in)/720 by (0.680 in)(25400 µm/in)/480 = 32
  by 36 µm = 32:36 = 8:9 aspect ratio.
  [7] Criticism: H.262 claims that SAR is a "ratio", then, as it does
  with DAR, wrongly defines it as a quotient (which it turns
  upside down).

--
What if you woke up and found yourself in a police state?
African-Americans wake up in a police state every day.
___
ffmpeg-user mailing list
ffmpeg-user@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-user

To unsubscribe, visit link above, or email
ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".

Re: [FFmpeg-user] Glossary: DAR, PAR, and SAR

[Mark Filipak (ffmpeg)]

On 09/30/2020 06:08 PM, Jim DeLaHunt wrote:

On 2020-09-30 13:09, Mark Filipak (ffmpeg) wrote:
I seek your comments regarding the following glossary entries (that have been reformatted to fit 
email). Kindly take your time.


-Mark.

DAR (display aspect ratio [1]) [noun]: 1, … as a minimized, H:V, integer ratio 
(e.g.
  16:9, 4:3)…
(and similar wording for PAR and SAR):



Is the term "minimized aspect ratio" already used in this domain? If not, then the related 
mathematics term "reduced fraction" may be a better inspiration than "minimized".


Excellent! I'll go for it.


SAR [noun]:…
  [2] A standardized set of picture sizes & aspects has been
  established:
 display DAR picture PAR    SAR = DAR/PAR
    16:9-2160: 3840 x 2160  16:9 : 3840 x 2160  16:9 :  1:1
 4:3-2160: 2880 x 2160   4:3 : 2880 x 2160   4:3 :  1:1
    16:9-1080: 1920 x 1080  16:9 : 1920 x 1080  16:9 :  1:1
 4:3-1080: 1440 x 1080   4:3 : 1440 x 1080   4:3 :  1:1
 16:9-576: 1024 x 576   16:9 :  720 x 576    5:4 : 64:45
  4:3-576:  768 x 576    4:3 :  720 x 576    5:4 : 16:15
 16:9-480:  853 x 480   16:9 :  720 x 480    3:2 : 32:27
  4:3-480:  640 x 480    4:3 :  720 x 480    3:2 :  8:9  [3] 



The formatting of the email garbles the table [2] enough that I can't be sure what I'm reading. 
Maybe insert printable delimiters into each line?


Hmmm... It's a table: rows and columns, like a spread sheet. Does making the column headers more 
obvious work better?


  display DAR   picture PAR  SAR = DAR/PAR
===   ===   =
16:9-2160:  3840 x 2160  16:9  :  3840 x 2160  16:9  :   1:1
 4:3-2160:  2880 x 2160   4:3  :  2880 x 2160   4:3  :   1:1
16:9-1080:  1920 x 1080  16:9  :  1920 x 1080  16:9  :   1:1
 4:3-1080:  1440 x 1080   4:3  :  1440 x 1080   4:3  :   1:1
 16:9-576:  1024 x 576   16:9  :   720 x 5765:4  :  64:45
  4:3-576:   768 x 5764:3  :   720 x 5765:4  :  16:15
 16:9-480:   853 x 480   16:9  :   720 x 4803:2  :  32:27
  4:3-480:   640 x 4804:3  :   720 x 4803:2  :   8:9  [3]

Or is it the column centering that doesn't work?

--
What would you do if you woke up in a police state?
African-Americans wake up in a police state every day.
___
ffmpeg-user mailing list
ffmpeg-user@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-user

To unsubscribe, visit link above, or email
ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".

Re: [FFmpeg-user] Glossary: DAR, PAR, and SAR

[Jim DeLaHunt]

On 2020-09-30 15:08, Jim DeLaHunt wrote:

On 2020-09-30 13:09, Mark Filipak (ffmpeg) wrote:

SAR [noun]:…
  [2] A standardized set of picture sizes & aspects has been
  established:
 display DAR picture PAR    SAR = DAR/PAR
    16:9-2160: 3840 x 2160  16:9 : 3840 x 2160  16:9 : 1:1
 4:3-2160: 2880 x 2160   4:3 : 2880 x 2160   4:3 : 1:1
    16:9-1080: 1920 x 1080  16:9 : 1920 x 1080  16:9 : 1:1
 4:3-1080: 1440 x 1080   4:3 : 1440 x 1080   4:3 : 1:1
 16:9-576: 1024 x 576   16:9 :  720 x 576    5:4 : 64:45
  4:3-576:  768 x 576    4:3 :  720 x 576    5:4 : 16:15
 16:9-480:  853 x 480   16:9 :  720 x 480    3:2 : 32:27
  4:3-480:  640 x 480    4:3 :  720 x 480    3:2 : 8:9  [3] 


The formatting of the email garbles the table [2] enough that I can't 
be sure what I'm reading. Maybe insert printable delimiters into each 
line?



Hmm. When formatted with a fixed-pitch font, this table is legible.

I mostly withdraw my comment. The table is displayed with a fixed-width 
font as a I receive it from the ffmpeg-user list, both your (Mark F's) 
original message and my reply.  My email client turns it into a 
variable-width font when I quote it in my reply.


Printable delimiters would still be a help for when the table gets 
displayed with variable-width fonts, but the tradeoff is more in favour 
of relying on fixed-width font instead.


 —Jim DeLaHunt


___
ffmpeg-user mailing list
ffmpeg-user@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-user

To unsubscribe, visit link above, or email
ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".

Re: [FFmpeg-user] Glossary: DAR, PAR, and SAR

[Jim DeLaHunt]

On 2020-09-30 13:09, Mark Filipak (ffmpeg) wrote:
I seek your comments regarding the following glossary entries (that 
have been reformatted to fit email). Kindly take your time.


-Mark.

DAR (display aspect ratio [1]) [noun]: 1, … as a minimized, H:V, 
integer ratio (e.g.

  16:9, 4:3)…
(and similar wording for PAR and SAR):



Is the term "minimized aspect ratio" already used in this domain? If 
not, then the related mathematics term "reduced fraction" may be a 
better inspiration than "minimized". See 
. "Reduced aspect 
ratio"? "Ratio where the two numbers have a greatest common divisor of 1"?


Also,



SAR [noun]:…
  [2] A standardized set of picture sizes & aspects has been
  established:
 display DAR picture PAR    SAR = DAR/PAR
    16:9-2160: 3840 x 2160  16:9 : 3840 x 2160  16:9 :  1:1
 4:3-2160: 2880 x 2160   4:3 : 2880 x 2160   4:3 :  1:1
    16:9-1080: 1920 x 1080  16:9 : 1920 x 1080  16:9 :  1:1
 4:3-1080: 1440 x 1080   4:3 : 1440 x 1080   4:3 :  1:1
 16:9-576: 1024 x 576   16:9 :  720 x 576    5:4 : 64:45
  4:3-576:  768 x 576    4:3 :  720 x 576    5:4 : 16:15
 16:9-480:  853 x 480   16:9 :  720 x 480    3:2 : 32:27
  4:3-480:  640 x 480    4:3 :  720 x 480    3:2 :  8:9  [3] 



The formatting of the email garbles the table [2] enough that I can't be 
sure what I'm reading. Maybe insert printable delimiters into each line?


Best regards,
    —Jim DeLaHunt


___
ffmpeg-user mailing list
ffmpeg-user@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-user

To unsubscribe, visit link above, or email
ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".