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发信人: zzn (爱你到内伤), 信区: Network
标题: mms协议英文资料(07)
发信站: 哈工大紫丁香 (2003年08月23日10:52:15 星期六), 站内信件

Ok. This is where it gets interesting.
Until now, there has been no information available whatsoever regarding
details of the MMS protocol. Extensive internet searching and library reading
was all fruitless. Many emails and even more hours spent on the internet gave
no results with a seemingly closed shop Microsoft policy saying nothing about
the protocol. It all seemed to be going nowhere. Downloading from a streaming
server site with its HTTP protocol enabled was possible using the widely
available ASF recorder program but sites using MMS protocol were ‘view on
line’ only. That is, until now :0)
Streaming protocols – what else
Streaming over the internet in real time has certain requirements. Viewers
must be able to experience the media held on or going through the streaming
server as it actually happens. Real time streaming means that you need a
system that will carry the video or audio file with a time reference to your
player with the minimum of fuss and download time. Making the player easy to
use is important in order to allow anyone with basic computer knowledge to go
on line and view the media. Also, many viewers need to be able to view media
files or live shows simultaneously.
Microsoft developed MMS to do this, but never released any information about
the protocol. MMS is Microsoft’s equivalent, but not compatible to, Real
Networks RTP protocol. That being an open protocol with well documented
details available on the net. In fact, Real Audio player pro version actually
has a record button on it! Other software like XfileGet also downloads RTP
and is available to those interested in downloading RealAudio media.
These are my findings and experiments on MMS and are explained as fully as
possible. Please remember that additions will be inserted as time goes by
because this document is not complete. Understand that with no data from
Microsoft themselves means that the whole project is still in its
experimental stages. However, enough knowledge has been gained to enable me
to draft this document, and ultimately write software to actually download
streamed ASF or other Windows media files straight onto a local hard disk.
These are my own personal findings, THIS IS NOT A FULL PROTOCOL DESCRIPTION,
so don’t blame me if things are not 100% accurate.
So let’s start here – Packets and Streams
MMS protocol is transmitted from the server to the viewer in the form of
packets, blocks of data send over the internet, straight to your computer. A
media file held on the server can typically be in the form of an ASF or WMV
type format. Live broadcasts via a streaming server also consist of packet
data. A packet may consist of multiple ‘streams’ in the case of TV/video or
maybe only one stream in the case of a radio station audio broadcast. You can
think of multiple streams as being mixed or combined into one actual packet.
The streams sent within a packet depend on the type of media content. More
about streams later.
There are two distinct types of MMS protocol packet: Command packets and
Media packets.
First, let us deal with command packets
MMS protocol uses a selection of commands for various jobs like connecting to
the streaming server, requesting a file, acknowledging that the link is still
in place as well as other tasks like end of file indication, lost packet
requests and things like that. This is application level protocol and it’s
at this level where the media viewer and server actually communicate and
negotiate crucial information regarding the packet streams. This is all
transparent to the viewer at home.
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白天奔忙于生活的人/傍晚就三三两两走到一起：/是南方这样的温暖时常发生

路草长满街道/幸与不幸从不同的着落点退出/他们错过记忆里的某件事/
仿佛一只只岩鹰/方向改变了身体仍在憧憬中/越过一座座灰色的城市

※ 来源:·哈工大紫丁香 bbs.hit.edu.cn·[FROM: 202.118.243.49]

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