Network Services Status

Susanne Lefvert lefvert at mcs.anl.gov
Wed Nov 24 11:54:10 CST 2004


Here is an update on network services. Feel free to give comments.


Selector
=========

Current State:
--------------
Selecting a video stream works well for both Quicktime and VIC.  Selecting 
audio works for the first stream, however, switching to a new stream 
causes Quicktime to fail.

Suggested Improvements:
-----------------------
* Recreate timestamps in rtp packages to make audio switching work 
properly
* Enable multiple stream selection
* Separate UI from service and make it run on Windows


Transcoder:
===========

Current State:
--------------
I used rat3 that can transform linear16 8kHz <-> pcmu 8kHz.  An AG venue 
can, based on client capabilities, connect to the transcoder and send back 
appropriate streams to the clients.

Suggested Improvements:
-----------------------
* Find/implement a transcoder that is capable of transcoding linear16 
16kHz <-> pcmu 8kHz.


Broadcaster
============

Current State:
--------------
When pointed at a venue, the broadcaster retrieves multicast addresses and 
starts the Selector for video and the Transcoder/Mixer (rat3) for audio.  
The selected video stream and mixed audio stream are sent to new 
multicast/unicast addresses.  Next, the broadcaster writes a session 
description file and starts a web server where the sdp file is published.  
Quicktime can then be started from a URL and play back audio and display 
video from the venue.

Suggested Improvements:
-----------------------
* Quicktime can only play back pcmu 8kHz audio.  Find/create a 
mixer/transcoder that can perform linear16 16kHz -> pcmu 8kHz. (Quicktime 
fails when using rat3 as a transcoder in linear16 8kHz -> pcmu 8kHz mode)
* Integrate a QuickBridge so we can send to more than one unicast address.
* Audio is delayed ~2 seconds compared to video.


Schemas
========
Prototype xml schemas for node services and nodes can be found at: 
http://www-unix.mcs.anl.gov/~lefvert/AGEP/AGEP-0128.html


/Susanne




More information about the ag-dev mailing list