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
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