[Live-devel] Live555 MPEG2 Transport Stream packet loss

[xcsmith at rockwellcollins.com]

I am willing to work with anyone who wants to help in order to solve our
problem (...) I do not imply that the source of the problem is software,
however, from our observations it's hard to conclude that the WAN is to
blame (although it's the first impression). I am trying to make the server
to send packets which would go through the WAN without problems. Please be
assured - we have enough bandwidth to send the data. And also - reducing
max packet size DID have some impact on the lost packets vs received
packets ratio, not perfect, but it DID improve the sittuation to some
degree.

Re: Maybe this is a newbie idea, but did you check the TTL?  I thought the
default set by the LIVE should be pretty low.  I'm no network buff, but my
understanding is that if TTL is too low, "repeaters" down the line will
drop the packet after a few hops.   How are you checking which packets have
gone missing in Ethereal?  Are you seeing gaps in the RTP sequence numbers
of arriving packets?  You can also use ethereal to look at the RTCP RR
(receiver report) your client (VLC) is sending, in which it will report
packet loss.  What happens if you request the stream via UDP?  Does the
stream get worse or stay about the same?  Ross should please correct me
here, but does TCP offer that much benefit over UDP for real-time video
playback?  If a packet arrives too late, it won't be useful except when
doing a recording.

Also, your email says you are using ATM (Asynchronous Transfer Mode?).  I
check this on wikipedia, and notice that the data must be divided into very
small cells for delivery.  It seems like ATM is a protocol for
time-sensitive data, like VoIP.  RTP also is designed to meet special
timing needs of the data. Could there be a problem combining these two
time-sensitive protocols?  "If a circuit is exceeding its traffic contract,
the network can either drop the cells or mark the Cell Loss Priority (CLP)
bit (to identify a cell as discardable further down the line)."  The RTP
delivery can be somewhat bursty, so maybe you need to check your ATM
contract and make sure you have the correct one (VBR maybe?) one?

Well, I hope there are some ideas here anyway.  I'd be interested in
hearing what you find out, I also have some packet loss in my system, but I
think it's resource or OS related for me.
Xochitl