Opened 3 years ago

Last modified 3 years ago

#3798 new defect

ffprobe indentifies 16:9 display aspect ratio as 0:1

Reported by: miguelapg Owned by:
Priority: normal Component: ffprobe
Version: git-master Keywords:
Cc: Blocked By:
Blocking: Reproduced by developer: no
Analyzed by developer: no

Description

Summary of the bug:

ffprobe indentifies wrongly 16:9 display aspect ratio as 0:1 in this movie "pompeii-tlr2_h1080p.mov". (Uploaded to "incoming" folder in your FTP server: upload.ffmpeg.org)

How to reproduce:

ffprobe -v quiet -print_format json -show_format -show_streams "pompeii-tlr2_h1080p.mov" >"myResults.json"

ffprobe version
Latest version: git-a613257 (2014-07-23) 64-Bit

ffprobe output in Json format is attached to this ticket. Called: "myResults.json".

Attachments (1)

myResults.json (4.9 KB) - added by miguelapg 3 years ago.
Output in Json Format showing 0:1 as aspect ratio instead of 16:9

Download all attachments as: .zip

Change History (8)

Changed 3 years ago by miguelapg

Output in Json Format showing 0:1 as aspect ratio instead of 16:9

comment:1 Changed 3 years ago by cehoyos

Is this a regression (did it work with an older version of FFmpeg)?
Is the problem only reproducible with ffprobe or also with ffmpeg?

comment:2 Changed 3 years ago by Cigaes

I suspect you confuse sample aspect ratio and display aspect ratio.

ffprobe shows 0/1 for the sample aspect ratio, meaning it is not explicitly defined in the stream. Players usually treat it as 1.

Your video has resolution 1920×816; assuming the sample aspect ratio is 1, that makes the display aspect ratio approximatively 2.35, which is a very standard aspect ratio for cinema movies. There is no 16/9 here, except probably for the initial content that was later cropped.

comment:3 Changed 3 years ago by miguelapg

You are right this video is not 16:9. I was wrong in the subject.

The subject should be: ffprobe is showing the wrong display aspect ratio.

Please, have a look at the JSON file and you will see how is adding "0:1" to "display_aspect_ratio" and to "sample_aspect_ratio"

Forget I said this video was 16:9.

Thanks

comment:4 Changed 3 years ago by heleppkes

0:1 is the value for invalid/unset aspect ratio. It could be argued that it shouldn't be shown at all in this case, but its not wrong as an absence of AR is usually just interpreted as square pixels.

comment:5 Changed 3 years ago by Cigaes

As I explained earlier, 1/0 means that the aspect ratio is not declared by input file. Players will just assume square pixels and thus 2.35 aspect ratio, but that could as well mean a broken muxing software.

comment:6 Changed 3 years ago by miguelapg

OK, I understand.

I think the problem here is also to understand what is "0:1", because is not something simpler like "n/a", "nan" or "null", etcetera.

A clear reference in manuals will help a lot.

I do mention this because if I had known what is "0:1", alternatively I can calculate display aspect ratio dividing width by height instead of, and optionally.

Thanks

comment:7 Changed 3 years ago by cehoyos

  • Keywords aspect ratio removed
  • Priority changed from important to normal
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