[MPlayer-dev-eng] FYI: Overview of Microsoft Windows Media 9 Serie

[Bertrand Baudet]

I was at the ms wm summit those last 2 days, and I will try to give you
an overview on the changes/new techno they have done.

Before people start flaming me, I'm not trying to make you switch to 
windows, not at all. As you may already have seen, we start receiving
bug report on some mms url. So far those bugs are related to the new 
WMS9 (window media sever). By knowing the changes made by MS, 
that might give us an idea on why some bugs are happening.

What they call the "Windows Media 9 Serie" (WM9S) it's a collection
of news things:
	- new player
	- new server
	- new encoder
	- new codecs (audio/video)
	- new DRM

I will describe only the tech that are interesting for us.


New streaming technologies:
=====================
They added support for RTSP/RTP and are going to slowly drop the mms protocol.
They didn't specify why this move toward RTSP, but I'm guessing is to allow
the cache appliance(HW) to use a standard protocol and avoid ms to release
there mms protocol. Anyway, for what they said, they get better performance
with RTSP/RTP than mms.
They called "legacy support of mms" on there new client/server 9 version.
They removed the mms protocol on there server/server connection.

FastStart: 
Remove the buffering time when streaming from the net.
Allow the player to start with zero buffering. The client will
report its bandwith and the server will send the packets at a multiple
of the bitrate, so the player's buffer will be progressivelly filled.
The player doesn't wait for the buffer to be filled, it immediately starts
playing. It gives the impression that the movie is stored locally.

FastCache:
cache the movie on the HD, at the same time as the movie
is played. Allow futur play of the movie from the HD instead of the net to
eliminate network connectivity trouble.


Player:
=====
Video smoothing: 
Plugin that allow the insertion of autocreated frames.
For example on a movie playing at 10 frames per sec, you can see the
flickers. The plugin will autogenerate(interpolation?) 1 frame between 2
frames to make the movie smoother.


Codecs:
======
Scalable:
With the previous version of there codec (WMC8) you will have
as many streams in the file as bandwith you want to target.
56k, 100k, 300k was 3 independant streams.
Now the WMC9 encode at 300k and can generate the other 
bitrate from the 300k stream.


Encoder:
=======
Nothing really interesting here, they now allow you to create
movie from still images, with zoom on them, fade between them
and other fancy stuff.


DRM:
====
They used code offuscation technic in there new implementation...
(I just remember that because it made me smile :p )

ASF format:
=========
Updated to allow new features for the WM9S.
Support for non-square pixel for example:
pixel aspect ratio is saved in the ASF file header.
(pixel aspect ratio and resolution are now 2 separates
parameters)
They said, they have updated the ASF spec on there web site.
(http://www.microsoft.com/asf) ... still the same spec I already have...


Note on the file extensions:
.WMA for files that include audio compressed with the Windows Media Audio
 codec, or 
.WMV for files that include both audio and video compressed with Windows Media
 Audio and Windows Media Video codecs. 
Content compressed with other codecs should be stored in file and use the .ASF 
extension. 


Bertrand