[openbeosmediakit] communication with MCF, XVID teams

  • From: "shatty" <shatty@xxxxxxxxxxxxx>
  • To: openbeosmediakit@xxxxxxxxxxxxx
  • Date: Wed, 07 Aug 2002 21:41:11 -0700

Hello all,

Just to keep you appraised of my progress, here's a little note.  I have st=
arted speaking with the MCF folks about their requirements for an extract=
or API and what they are expecting out of a decoder API.  I've exposed th=
em to the Media Kit API via the annotated bebook.  I also sent a few of t=
hem the header files for the media kit.

The response is strongly positive.  One coder in particular is very excited=
 about the prospects of MCF and OBOS.  He's also a follower of osnews and=
 familiar with BeOS to some extent.  He's trying to recommend that they p=
ush the Be Media Kit API as a cross platform solution.  That aspect is pe=
rhaps not so important for us, but what I see is this: =20

They are going to help us write the API (extractor/decoder), and their core=
 code will be written to our API.  Because of this, we will have a clean =
and fast implementation of MCF that meets these specifications.  Also, I =
anticipate that some of the MCF team will be moving to OBOS when possible=
 to continue development of the MCF specification and maintain code.  Thi=
s is a good thing.

I have only recently started speaking with the XviD folks, although I built=
 the xvid core library on beos with minimal problems.  Their API is rathe=
r simple (about 2 pages)  I'm planning to join with the team to ensure fu=
ture beos build compatibility, and to generally keep them aware of the OB=
OS platform.

At this point I'd like to ask that anyone who is familiar with quicktime, d=
irectshow, gstreamer or something similar please contact me.  In particul=
ar if you have also programmed the media kit API.  Also the questions abo=
ut the media kit API are getting a little bit technical for me in some re=
spects since I have not pushed the media kit API very hard.  (My work in =
nplay was basically using the MediaFile, MediaTrack wrappers, and my work=
 in HybridDivx was mostly bit twiddling and experimentation rather than c=

For example, here's a question that I don't know the answer to from one of =
the MCF developers:
* I didn't check, but is there a way to play an
audio file backward (or video file) ? Like connecting everything, using Sta=
rt() and then it plays backward.

Other things that they are concerned about that I am fuzzy on: if I use thi=
s constructor:
BMediaDecoder(const media_format *inFormat,
      const void *info =3D NULL, size_t infoSize =3D 0)

How does the Kit pick a decoder?  It seems to be "first-come-first-served",=
 but is there a way to configure it? (they were talking about "priorities=
" of some sort, that I think that in DirectShow they map to a linear orde=
ring, or something like that.)

They are also interested in determining how "fast" a node is, although I po=
inted out to them that this depends on a wide variety of factors.  I thin=
k that they want to be able to specify an input and output format and hav=
e the kit figure out the "best" way to get from A to B.  AFAIK it doesn't=
 do that kind of thing.  (and I'm not sure it's a very well defined task,=

Any help is appreciated.  Also, if anyone has Media Kit API specs for forme=
r versions of BeOS I would be interested.


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  • » [openbeosmediakit] communication with MCF, XVID teams