[MPlayer-dev-eng] MCF ( Multimedia Container Format ) : Invitation to participate

[Alban Bedel]

Hi Arpi,

on Wed, 5 Jun 2002 14:27:16 +0200 you wrote:

> Hi,
> 
> > > 2. asf, mpeg-ts (+ogg?) style: fixed size chunks, so raw seeking is
> > > possible (chunk position can be calculated). these chunks contain the real
> > > data chunks fragmented. i like this approach, imho it's the best we can
> > > have: raw seeking is possible without index, error-resistant, any size of
> > > the real data chunk is allowed, no mess with sync-words.
> > in ogg streams the raw codec data is grouped into pages, these pages are spl
> > it over fixed size packets. The packet header allows to identify wether the pag
> > e 
> > starts in this package or continues in the next package.
> 
> great!
> 
> so, ogg is similar to asf/mpeg-ts. so, why do we need new fileformat then?
> ogg uses timestamps, and has avi-style headers.
> 
These ogg have sevral problems, the main one imho is vorbis. Even if a regular
ogg/vorbis player can't play the audio track of an ogg movie with vorbis audio, the
vorbis audio is embedded like in an audio only ogg/vorbis. It's good for us, a single
demuxer can parse them, but it's pain because it must be handled in a different way
all the time. That's not so important but you must add to this the fact that only the
pages have timestamp. So when a page contain more than one packet (usal with
audio) only 1 packet is timestamped and you must calculat the other. Not so hard,
but once again vorbis kick in. You need some data from the decoder to be able to
have the length of a packet in order to calculat the other timestamp. Thus for vorbis
audio you can't have all packets timestamped without at least initing the decoder.
For video and other audio format it's the same problem, because only a few packet
have a timestamp you can't really do variable fps.
In fact I belive that the author wanted to only adress the sync issue there is under
windows with avi, and make seeking a little easier. I can't see any real advantage
in this format. I hope we'll be able to support the 2 other feature it have : embeded
subtitles and chaptering, but it's far from beeing the perfect format.
Dunno much about mcf, but I think that if we work together (with other moive player
dev teams ?) it can perhaps lead to the "perfect" format for both devellopper and
end-user.
	Albeu