Opened 8 months ago

Closed 8 months ago

#6176 closed defect (fixed)

Use of non-standard value (4) for displayUnit in webm containers

Reported by: theo Owned by:
Priority: normal Component: avformat
Version: git-master Keywords: mkv
Cc: jyx@fb.com Blocked By:
Blocking: Reproduced by developer: yes
Analyzed by developer: yes

Description

Hi,

Starting ffmpeg 3.2.x we have noticed that for Webm containers, ffmpeg sometimes (quite often for us actually) sets the displayUnit field to a value of '4' (likely from here: https://github.com/FFmpeg/FFmpeg/blob/e7dec52d4da7fad61f65529d5a396968e3dfe777/libavformat/matroskaenc.c#L1245 ). I believe that according to the Webm documentation https://www.webmproject.org/docs/container/#DisplayUnit '4' is not a valid value for Webm containers.

You can find link to a file to repro on this Shaka-packager thread: https://github.com/google/shaka-packager/issues/192 as well as previous discussion related to this.

How to reproduce:
ffmpeg version 3.2+

ffmpeg -i original.mp4 -c:v libvpx-vp9 -pass 1 -b:v 0 -crf 33 -r 30 -threads 8 -speed 4 -tile-columns 6 -frame-parallel 1 -g 60 -an -f webm -y /dev/null
ffmpeg -i original.mp4 -c:v libvpx-vp9 -pass 2 -b:v 0 -crf 33 -r 30 -threads 8 -speed 4 -tile-columns 6 -frame-parallel 1 -g 60 -auto-alt-ref 1 -lag-in-frames 25 -c:a libvorbis -b:a 64k -f webm -y input.webm

Original file https://www.dropbox.com/s/4hhx3o1hs89f5q3/input.webm?dl=0

Thanks!

Change History (1)

comment:1 Changed 8 months ago by jamrial

  • Analyzed by developer set
  • Component changed from undetermined to avformat
  • Keywords mkv added; webm matroska aspect ratio removed
  • Reproduced by developer set
  • Resolution set to fixed
  • Status changed from new to closed
  • Version changed from 3.2.1 to git-master

Displayunit with value 4 is valid for Matroska, but you're right that it's not for WebM.

Fixed in 1ad60e4e70ecc71b1301bdc041fa133129338393 (git master) and 36fff6c75459a7e23ad04be60264643e9c3d2ce8 (release/3.2)

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