[FFmpeg-devel] Why the tag “DURATION” is a necessity in Matroska files?

[wm4]

On Fri, 16 Jun 2017 15:43:51 +0200
21naown at gmail.com wrote:

> Le 16/06/2017 à 14:25, wm4 a écrit :
> > On Fri, 16 Jun 2017 13:51:20 +0200
> > 21naown at gmail.com wrote:
> >  
> >> Le 16/06/2017 à 12:55, wm4 a écrit :  
> >>> On Fri, 16 Jun 2017 02:32:10 +0200
> >>> 21naown at gmail.com wrote:
> >>>     
> >>>> Hello,
> >>>>
> >>>>
> >>>> I would like to know why the tag “DURATION” in Matroska files (.mkv) is
> >>>> a necessity? Even mkvmerge lets the choice to use it or not with
> >>>> “--enable-durations”, in addition it is written “Write durations for all
> >>>> blocks. This will increase file size and does not offer any additional
> >>>> value for players at the moment.” (source
> >>>> https://mkvtoolnix.download/doc/mkvmerge.html#d4e535).
> >>>>
> >>>> Possibly linked to
> >>>> http://git.videolan.org/?p=ffmpeg.git;a=commitdiff;h=31852540d4fba0c4e8a16d0b3ddff08fc98e48fd  
> >>> As far as I'm aware, the linked commit does not do the same thing as
> >>> the mkvmerge option you pointed out.  
> >> Yes that is why I wrote “possibly”, also because this commit is the one
> >> which adds the tag “DURATION” as a necessity, but a necessity that no
> >> software seems to use and it is not even a standard in the Matroska’s
> >> documentation if I am not mistaken. So the fact that it is a necessity
> >> and not a choice is the main problem.  
> > Who says it's a necessity or standard? It's just what mkvmerge does.
> > Since the patch is by google, I assume google has some use for it
> > (there might also be a discussion about it on the ML).  
> 
> Sorry for the bad word “necessity”, it is better with “imposed”. Could 
> you let the choice to the user like mkvmerge with 
> “--disable-track-statistics-tags”?

We could add a private option to the ffmpeg matroska muxer to disable
writing this tag, and we could even switch that option off by default
(so the tag isn't written unless the user explicitly requests it). Feel
free to propose a patch.