Subject: [Fwd: Re: [AVT] WGLC: draft-ietf.avt-ulp-19.txt]

From: Andrea Lorenzo VITALI <[email-masked]>
Date: Thu, 30 Nov 2006 09:59:07 +0100

-------- Original Message --------
Subject: Re: [AVT] WGLC: draft-ietf.avt-ulp-19.txt
Date: Thu, 30 Nov 2006 09:58:53 +0100
From: Andrea Vitali <[email-masked]>
To: Steve Underwood <[email-masked]>
References:
<[email-masked]>
<[email-masked]> <[email-masked]>

> Could you point to some end points actually using RFC2733? I've been
> trying to find some real world implementations of RFC2733, and I've come
> up blank. I noticed someone recently asked on this list if anyone had
> implemented RFC2733, and there seemed to be no reply.

We, in STMicroelectronics, implemented RFC2733 for VoIP in software.

RFC2733 was very effective when the amount of redundancy added was tuned
based on packet-loss-rate estimates.

Otherwise, when you use RFC2733 without real-time adaptation based on
packet-loss-rate, either you have too much redundancy or you have too
less redundancy. In the former case you are wasting bandwidth, in the
latter you cannot recover losses.

> I am currently interested in implementing RFC2733 for T.38 over RTP.

If you are interested, we can setup things to share the C code.

I wrote both: an RFC2733 encoder and a smart RFC2733 decoder.

For the encoder, you can easily set the FEC scheme of your choice.

For the decoder, you can set the amount of memory for data packets and
for FEC packets. You need not to specify the FEC scheme you have chosen
at the encoder. The decoder can handle any scheme.

> RFC2733. In the real world it seems everyone uses only the redundancy
> option, and important packets are sent multiple times.

Obviously, redundant encoding schemes are media specific, while FEC can
handle any kind of data.

Sending multiple times important packets is the simplest FEC scheme,
that is (N,1): 1 data packet sent N times. RFC2733 allows (N,K): K data
packets sent with N-K redundancy packets.

Regards,

  Andrea

-- 
 ______________________________________________________________

  Andrea VITALI                            [email-masked]

  tel (+39) 039 603 7244             mobile (+39) 347 93 08 433
  fax (+39) 039 603 6129

  STMicroelectronics
  Centro Direzionale COLLEONI - Palazzo "DIALETTICA"
  20041 Agrate Brianza (MI) ITALY
 ______________________________________________________________

-- 
 ______________________________________________________________

  Andrea VITALI                            [email-masked]

  tel (+39) 039 603 7244             mobile (+39) 347 93 08 433
  fax (+39) 039 603 6129

  STMicroelectronics
  Centro Direzionale COLLEONI - Palazzo "DIALETTICA"
  20041 Agrate Brianza (MI) ITALY
 ______________________________________________________________

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