[M4IF Technotes] Transport of MPEG-4 SL Packets (Bifs and ODs) over HTTP and IP

[John Arthur]

Hello Graham,
There are ways to recover lost packets in RTP, based on the receiver
reports provided through the RTCP channel. However since the report
frequency can vary it can take some time before the lost packet
information is received on the server. Moreover these reports have to be
manually interpreted on the server side to determine how many packets
have been lost and which. The client must also stop processing BIFS
updates when an out of sequence packet is received, and wait for the
packet with the right sequence number.
This introduces the need for local caching mechanisms on client and
server side, to accomodate resending of lost packets (server) and
storage of received packets while waiting for the right packet to come
along (client). This seems unnessarily complex when the TCP subsystem
handles this kind of functionality innately.
Also the receiver reports didn't work on the OpenSource RTP
implementation we used [jrtp lib] :-(. So we had to implement our own
work around.
Since the whole thing is built on UDP/IP, packet loss is very sensitive
to network conditions, it is especially unhappy in wireless
environments, where hundreds of packets can sometimes go astray, which
is catastrophic for a streaming BIFS session.
Anyway TCP/IP seems a much better bet for BIFS streams, hence my
original question.
Do you have any other opinions/experince re: RTP for BIFS?
Best regards
John
-----Original Message-----
From: technotes-admin   lists.m4if.org
[mailto:technotes-admin   lists.m4if.org] On Behalf Of the_ether
Sent: 28 February 2024 16:14
To: technotes   lists.m4if.org
Subject: Re: [M4IF Technotes] Transport of MPEG-4 SL Packets (Bifs and
ODs) over HTTP and IP
I thought that RTP handled resend requests in case of packet loss.
There are also the extensions to RTP (RTPS?) for secure data, so I'm
surprised you have problems with packet loss.
Regards
Graham
----- Original Message ----- 
From: John  <mailto:john.arthur   octaga.com> Arthur 
To: 'AVARO Olivier  <mailto:olivier.avaro   rd.francetelecom.com>
FTRD/DIH/REN' ; technotes   lists.m4if.org 
Sent: Friday, February 28, 2024 1:46 PM
Subject: RE: [M4IF Technotes] Transport of MPEG-4 SL Packets (Bifs and
ODs) over HTTP and IP
Hello Olivier,
Our current implementation uses RTP (over UDP/IP) for BIFS SL Packets
but packet loss is a real headache, so I'm looking for an interoperable
TCP/IP solution.
Since we are talking about an MPEG-4 MU server, sending on-the-fly,
dynamic scene information which may vary according to clients
characteristics, I can't just send the content as a pre-generated mp4
file.
It seems that HTTP would not be appropriate for sending the raw IOD, ODs
and BIFS streams unless you defined specific MIME types for all types of
MPEG-4 streams, this seems a little long-winded.
The question is therefore: is there a pre-defined, interoperable way to
pack SL header data into a TCP/IP transmission, without using the RTP
mapping already defined (since this assumes use of RTP)? If not do we
need one?
Best regards
John
-----Original Message-----
From: technotes-admin   lists.m4if.org
[mailto:technotes-admin   lists.m4if.org] On Behalf Of AVARO Olivier
FTRD/DIH/REN
Sent: 28 February 2024 12:10
To: john.arthur   octaga.com; technotes   lists.m4if.org
Subject: RE: [M4IF Technotes] Transport of MPEG-4 SL Packets (Bifs and
ODs) over HTTP and IP
Hi John,
I've read many times in various places (including the recent MPEG-4
White Paper) that a method of transport of MPEG-4 streams over IP and
HTTP has been defined [by MPEG and IETF I assume]. However the only
documentation I can find only specifies transport over RTP.
Does anyone have any pointers as to where I can find documentation for
transport over general IP and HTTP? I am especially interested in the
transport of Bifs and OD SL Packets, and a common way of mapping SL
Packet Header info for protocols other than RTP, so as to ensure
interoperability for these protocols. 
If you use HTTP, I don't think you need to standardize anything, you
just download your MP4 file and play it.
If you are smart enough you can do some progressive download so that you
can play your file before it is completly received. 
Concerning streaming over IP, I guess you mean UDP/IP, you can use
MPEG-4 SLpacketized streams over UDP. Session description is not
standardize but for streaming people generally just use RTP.
What are exactly your requirements ? 
cu,
O.
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