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Re: [AVT] RFC3550 .... -> RTP light?
On Aug 18, 2004, at 2:39 PM, Ladan Gharai wrote:
An alternative to a RTP-light protocol would be a RTP profile which
satisfies the features you list.
The current version of the "RTP Profile for TCP Friendly Rate
Control" has the following properties:
1. is only defined for unicast flows (no multicast)
2. includes a 32 bit send timestamp and round trip time in the RTP
data packet
I'd be interested to know what other timing information media
applications would be interested in exchanging between unicast
sender/receivers which would be useful to add to the profile?
In the general case, N unicast streams generated from a
single sender, sent to N different receivers in the same
room, but in different boxes. Streams sent via Layer-2 of
Ethernet, 801.11, Firewire, whatever. Each of the boxes turns
the RTP stream into an analog audio waveform put on a cable,
the cable waveforms get mixed together in the analog domain
and sent to speakers.
The goal is single-sample synchronization between
the analog waveforms produced by the N receivers,
for N = 192 KHz (yes, this is the trendy sampling rate
these days in pro-land). Using only the Layer 2, no
coax for word clock, etc -- the goal is to reduce cable
madness.
Obviously, it takes more than a media protocol (be it RTP
or a new RTP-lite protocol) to make a system like meet spec --
we've talked about the problem in the past here, and earlier
work like the Flow Synchronization Protocol has been cited as
an example of a "helper" protocol one needs to add.
However, I do think that the features one builds into the media
protocol makes the problem easier or harder to do -- plain
vanilla RTP may make the problem harder than it needs to be.
Finally, a workshop is actually happening in Canada this
weekend about this very topic -- I won't be there, unfortunately,
but maybe an AVTer will be and could report:
http://www.banffcentre.ca/programs/program.aspx?id=154
---
John Lazzaro
http://www.cs.berkeley.edu/~lazzaro
lazzaro [at] cs [dot] berkeley [dot] edu
---
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