[FFmpeg-devel] [PATCH] attachments support in matroska demuxer
Thu Jan 3 03:27:22 CET 2008
On Thu, Jan 03, 2008 at 03:05:18AM +0100, Aurelien Jacobs wrote:
> On Thu, 3 Jan 2008 02:23:09 +0100
> Michael Niedermayer <michaelni at gmx.at> wrote:
> > On Thu, Jan 03, 2008 at 01:38:39AM +0100, Aurelien Jacobs wrote:
> > > On Sat, 29 Dec 2007 22:38:24 +0300
> > > Evgeniy Stepanov <eugeni.stepanov at gmail.com> wrote:
> > [...]
> > > Conclusions:
> > > - Attachment really looks like a stream itself. You can select
> > > the one you want to remux. For example the film poster would
> > > just be a jpeg stream with a single picture. The specificity
> > > of those streams would be:
> > > * contain one single packet
> > > * not pts
> > Contain no packets, just one global extradata, this was proposed already.
> > If you use normal packets there will be problems with them disapearing
> > if a stream is split timewise or if you seek before demuxing the
> > first packet.
> Hum... Indeed, using extradata has some advantages over normal packet...
> > Iam not completely happy with this use of streams but we will need some
> > solution and maybe its the least ugly, we will see ...
> > at least iam pretty sure extradata to be a better choice than 1 normal
> > packet
> Still it has at least one drawback: applications can't decode
> attached pictures as a normal stream. They will need some special
one could in principle use 1 packet and set the timestamp to the first
frame and the duration to the duration of the movie. In avi one could
choose a framerate so that the 1 frame is as long as the whole movie
i dont think this is a good idea though, iam pretty sure it would
cause alot of problems
> But, well, extradata may indeed be the best solution.
> > > - I think the only required API modifications to support this
> > > would be:
> > > * adding AVStream.filename and maybe AVStream.id_of_link_stream.
> > > * adding CODEC_ID_TTF ? (ugly, but shouldn't cause much trouble)
> > > * adding a way to mux ttf font in a separate file (maybe use
> > > a separate muxer for this, ie. call 2 different muxers from
> > > ffmpeg. seems ugly, but I've no better idea right now).
> > Well, there are a few more things i think
> > We need name / (mime) type to remux attachments
> > (CD Cover / ? / tiff)
> > (Fan art / image/x-photoshop / psd)
> > There also could be other things like Author, ...
> > Also we need a way to get the attachments to the decoders, yes we dont
> > have a ASS/SSA decoder but lets assume we had.
> I wonder if we really need this.
> It depends on what you consider a SSA decoder should do.
> Maybe a SSA decoder should just output some plain-text+formating
> (so that it can be re-encoded to another textual format), and thus
> it don't need the ttf file.
yes that would be ideal, it also seems that fabrice designed the
subtitle system toward this (uint16_t format; /* 0 = graphics */)
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
I know you won't believe me, but the highest form of Human Excellence is
to question oneself and others. -- Socrates
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