[FFmpeg-devel] [PATCH] AVPacket.display_duration

Michael Niedermayer michaelni
Tue Sep 9 06:07:12 CEST 2008


On Mon, Sep 08, 2008 at 07:21:09PM -0700, Baptiste Coudurier wrote:
> Hi guys,
> 
> Michael Niedermayer wrote:
> > On Tue, Sep 09, 2008 at 01:56:29AM +0200, Aurelien Jacobs wrote:
> >> Michael Niedermayer wrote:
> >>
> >>> On Fri, Sep 05, 2008 at 05:35:13PM +0200, Aurelien Jacobs wrote:
> >>>> Hi,
> >>>>
> >>>> For some subtitles track, each AVPacket must carry the display duration
> >>>> of the contained subtitle.
> >>>> The attached patch adds a dedicated AVPacket.display_duration field.
> >>> Iam not against this, but i would like to understand better for which cases
> >>> it is needed.
> >>>
> >>> plain UTF-8 and ASCII ?
> >> Exactly.
> >>
> >>> If so does mov, avi, asf, ... support plain UTF-8 and ASCII ?
> >> I don't think so...
> >>
> >>> if yes how do they know the display_duration ?
> >> The fact that they can't store any display duration just prevent
> >> them from storing plain text subtitles. At least I think so.
> >>
> >> Another possibility would be to not support any kind of plain text
> >> subtitles at all in ffmpeg. Demuxers could convert them to SRT,
> >> which is basically plain text + timing information. But I'm still
> >> not sure if I really like this solution.
> > 
> > iam fine with adding display_duration to AVPacket, the only minor
> > dislike i have with this solution is that codecs with very small
> > packets might see a minor speedloss with added fields. But then
> > not adding needed fields is no solution, some other solution for
> > these small packet audio codecs has to be found if it turns out that
> > the AVPacket handling overhead matters.
> > 
> > So again iam ok with adding display_duration.
> > 
> 
> So Matroska packets will have 3 kinds of duration ? normal, convergence,
> and display ? Or is display supposed to replace convergence ? Or am I
> missing something ?

There would be 3 different kinds of durations, i do not know if matroska will
set convergence_duration though, probably not.

I also do not know if this is the best solution, the obvious alternative
to display_duration is to have the matroska demuxer convert the codec
bitstream to a representation that contains the display_duration.
It seems that for all subtitle formats such representations exists, ASS as
well as plain text (SRT).

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Its not that you shouldnt use gotos but rather that you should write
readable code and code with gotos often but not always is less readable
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: Digital signature
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20080909/cfc13d11/attachment.pgp>



More information about the ffmpeg-devel mailing list