Subject: RE: [rohc] About RFC3321 SigComp Extensions

From: "West, Mark" <[email-masked]>
Date: Tue, 31 Jan 2006 23:18:15 -0000

Joel,

Shared mode is really rather SigComp specific; and in some respects is orthogonal to the choice of compression algorithm (I guess it depends how you define 'compression algorithm')?  Shared-mode can make available additional state information -- your algorithm would need to be extended to take advantage of this.  Typically, you are going to need to make *some* modifications to an off-the-shelf compressor to make it work efficiently with SigComp (*especially* with regard to the state model); shared-mode is just another consideration...

... we've implemented shared-mode.  In doing so, we found some concerns that are documented in the implementer's guide.  But, basically, we just hooked the provision of shared-mode state into our model of compression-state.  I realise that this is not a particularly helpful answer; but I suspect that most (if not all) compressors that can take full advantage of this are proprietary.

Cheers,

Mark.

-----Original Message-----
From: [email-masked] on behalf of Joel Centelles Martín
Sent: Tue 1/31/2006 6:08 PM
To: [email-masked]
Subject: [rohc] About RFC3321 SigComp Extensions
 
Hi All,

I'm currently working with the RFC3321 SigComp Extensions and I faced 
the following problem:

Implementing a sharing compression mechanism seems not to be hard work 
(draft-ietf-rohc-sigcomp-user-guide-04 gives a good way of doing it), 
the problem that I found is: Is there any compression algorithm that 
takes advantage of shared compression? I mean, is possible to implement 
the mechanism, store and access to the state in both sides, but, does 
anybody know about a compression algorithm that uses this information to 
improve compression rates? I've been searching in the web but found 
nothing about a compression algorithm of these characteristics.

About the same problem, do you know if there is anybody working to 
achieve it or to adapt an existing one to use it?

Thanks in advance,
Joël .

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