Hi everyone,
With the IETF meeting scheduled for next week in
Pittsburg PA USA, the current set of Internet-Drafts
about delivering MPEG 4 (and thus, Structured Audio) over
IP-based systems are now out; this would probably be a
good time for those interested in the topic to check in
on the status. This posting is a quick guide to what
to read and where.
The best place to start is this document:
A Framework for the delivery of MPEG-4 over IP-based Protocols
D. Singer & P. Westerink, Apple Computer & IBM, July 3 2000
http://www.ietf.org/internet-drafts/draft-singer-mpeg4-ip-00.txt
The basic message is that
-- there's probably going to be many different mappings of MPEG 4
to IP, not one
-- of these mappings, there may end up being a simple "default"
mapping of elementary streams (a single Structured Audio
file would be an elementary stream, FYI), that all tools
would be expected to stream and receive.
The default mapping the Singer & Westerink ID suggests
is found in this Internet Draft:
RTP Payload Format for MPEG-4 Streams
Civanlar, Basso, Casner, Herpel-Thomson, July 13, 2000
http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-mpeg4-03.txt
This document is simple enough to understand even if you're not
familiar with RTP (Real-Time-Protocol, the IETF way to stream media)
and describes some of the generic problems in using MPEG 4 Systems
under IP at all -- one of the options it lists as the possible
long-term solution is to literally build the IETF equivalent of all of
MPEG 4 Systems, and just end up using codecs (like Structured Audio)
from the MPEG lore.
The rest of the MPEG-4 over RTP ID's to be discussed next
week in Pittsburg are more complicated:
C.Roux et al., "RTP Payload Format for Flexmultiplexed MPEG-4
Streams", IETF Draft, draft-rgcc-avt-mpeg4flexmux-00, March, 09 2000
expires Sept 9 2000
http://www.ietf.org/internet-drafts/draft-rgcc-avt-mpeg4flexmux-00.txt
Yoshihiro Kikuchi et al., "RTP payload format for MPEG-4
Audio/Visual streams", IETF Draft, draft-ietf-avt-rtp-mpeg4-es-02,
July 6 2000,
http://www.ietf.org/internet-drafts/draft-ietf-avt-rtp-mpeg4-es-02.txt
C.Guillemot et al., "RTP Payload Format for MPEG-4 with Flexible
Error Resiliency", IETF Draft, draft-ietf-avt-mpeg4streams-00, March
1 2000, expires Sept 1 2000
http://www.ietf.org/internet-drafts/draft-ietf-avt-mpeg4streams-00.txt
C.Guillemot et al., "RTP payload format for MPEG-4 Visual
Advanced Profiles", IETF Draft, draft-gc-avt-mpeg4visual-00.txt,
March 1 2000, expires Sept 1 2000
http://www.ietf.org/internet-drafts/draft-gc-avt-mpeg4visual-00.txt
The MPEG 4 over RTP working group session is going to be multicast,
its on Thursday 3rd August 2000, 13:00-15:00 EST, for those of you who
might want to tune in, I won't be going to Pittsburg but I might be
tuning in to check out the discussion, if I can get it set up on my
machine in time.
Finally, one of the interesting tidbits in the Singer & Westerink ID
is that there's now an ad hoc MPEG Systems group that is defining an
actual file format for MPEG 4 Systems, so eventually there will be a
normative file format that tools like sfront can read and write, and
that MPEG 4 Systems streamers would be able to read and stream in
bulk ...
--jl
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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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