Re: [linux-audio-dev] Distributed audio processing

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Subject: Re: [linux-audio-dev] Distributed audio processing
From: John Lazzaro (lazzaro_AT_CS.Berkeley.EDU)
Date: Wed Oct 04 2000 - 20:03:56 EEST

> Please can somebody point me to information on using a LAN to distribute
> audio processing,
> i.e. setting one or more computers up as dedicated audio servers and
> streaming data between them?

I'd suggest starting here:
                                            
http://www.cs.columbia.edu/~hgs/rtp/faq.html

RTP is a transport protocol for shipping media around networks,
a product of an IETF working group. I'm currently embedding it
into sfront, and found that its very well thought out ...

http://www.cs.columbia.edu/~hgs/rtp/drafts/draft-ietf-avt-rtp-new-08.ps
http://www.cs.columbia.edu/~hgs/rtp/drafts/draft-ietf-avt-profile-new-09.pdf

are the main specs to understand, but there are main auxiliary
ones as well:

http://www.cs.columbia.edu/~hgs/rtp/drafts.html

RTP really makes sense if you intend to transport media around
either as unicast UDP packets or as multicast -- the packet
headers for sending the actual data have timestamps, sequence
numbers, and source identification, and there's a complementary
back-channel protocol, RTCP, for receivers to send info back to
senders. If the sort of applications you're doing are ones where
its vital for every audio data byte to be preserved, you can use
some combination of forward-error correction:

http://www.ietf.org/rfc/rfc2733.txt
http://www.ietf.org/rfc/rfc2354.txt

and resending packets when the sequence numbers indicate a lost packet:

http://www.ietf.org/internet-drafts/draft-ietf-avt-rtprx-00.txt

Once you buy into using RTP, you often end up having to deal with
controlling the media flows, and depending on your application the
various IETF MMUSIC standard might be useful, such as
Session Initiation Protocol:

http://www.ietf.org/rfc/rfc2543.txt

Session Description Protocol:

http://www.ietf.org/rfc/rfc2327.txt

or Real-Time Streaming Protocol:

http://www.ietf.org/rfc/rfc2326.txt

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John Lazzaro -- Research Specialist -- CS Division -- EECS -- UC Berkeley
lazzaro [at] cs [dot] berkeley [dot] edu www.cs.berkeley.edu/~lazzaro
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