[gst-devel] Tagging, media-info

[Thomas Vander Stichele]

El jue, 18-12-2003 a las 21:53, Benjamin Otte escribió:
> On Thu, 18 Dec 2003, Andreas Rottmann wrote:
> 
> > What do you mean by ported here?
> >
> Changed to use the new tagging system.
> 
> > I'm don't have very much insight into the code yet, could you be a bit
> > more verbose?
> >
> I didn't look at it for very long but for example it has a concept of
> streams and tracks per file, which isn't reflected anywhere in GStreamer.

It is.  For example, vorbisfile lets you seek to logical streams inside
an ogg.  If we don't handle this in GStreamer it's because we didn't add
it.  But all more modern container formats have a concept of
streams/tracks per file, and for good reason.  This includes matroska
and ogg.  Flac and shorten too IIRC.

Two examples of problems it solves:
a) Suppose you have ripped a CD to separate mp3 files.  There's no way
to play back those mp3's the same way as the album.  This is incredibly
annoying on, for example, live albums.  The way mp3 works it is
impossible to make the mp3's itself follow each other gaplessly.  No
amount of forensic hacking (adding mixing support, detecting silence,
...) will fix that.

b) Suppose you want to transcode a DVD to a video file.  Right now,
people either do one file per chapter, or one file for the whole video. 
Neither are satisfactory, and neither reflect the way you can play a
DVD.

So in the new media formats, which are treating the *user case*
correctly IMO, you clearly see there is a two-dimensional structure.
A file can consist of one or more frobs, where a frob is defined as "a
logical coherent unit of the transported media".  For example, one song
in a live set, or one chapter in a dvd.  Between frobs, it's even
possible that certain parameters change (sample rate, frame rate,
dimension, ...).

Each frob by itself can contain of one or more thwarks.  A thwark is
defined as "one unit of a base media type".  Thus, A frob could consist
of a video-only thwark, two language-specific thwarks for that video, a
PAL version of the video thwark, and five subtitle thwarks.

Whatever realworld names you give to frobs and thwarks, it is clear that
there is a very natural twodimensional structure to media formats today.

Which is why I don't think media-info is overengineered at all.  Could
it be better constructed than it is right now ? Sure.  But *please do
suggest something to remedy the matter*.  Don't just stop at saying
whether or not it is overengineered.  AFAIK, I've solicited actual
comments on the API of media-info on a number of times.  My intentions
to work with other people on this are pretty clear I would think :)

Anyway, some people have taken an interest as of late, so I will put my
plans for it online so we can work something out together.

Thomas

 
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