Subject: Re: [rohc] SigComp assembler and interpreter ?

From: Simran Suri <[email-masked]>
Date: Fri, 27 Feb 2004 12:31:32 -0600

Hi Carsten,
Thank you for your reply.

I understand the UDVM implementation is not the complete SigComp 
implementation, but as per my understanding it is the most significant 
part. The other components- compressors, state manager and the 
dispatchers (compression and decompression) can be built around the UDVM 
using open source components (e.g DEFLATE compression libraries etc.) 
Also, of these only the dispatchers would be higher layer/ application 
specific and thus may have IPR issues. Please correct me if I'm wrong.

So, I still have the following questions:
a) Has anyone provided a complete UDVM implementation that can be used 
in a SigComp module?
b) In your original implementation (of the -05 draft), how was the 
compressed message for "This is a test message.  What is the answer to 
life, the universe and everything ?" generated? Although the 
documentation says DEFLATE, I did not get the same result using the zlib 
DELFATE implementation. Did I miss something?
c) Is the decompression code for DEFLATE algorithm available in the UDVM 
instruction set or in bytecode?

Thanks once again.

Regards,
Simran

Carsten Bormann wrote:

> Hi Simran,
>
>> 2. Has there been any addition to the UDVM assembler/interpreter 
>> since March 2002? Specifically, has the implementation expanded to 
>> work with all the instructions in the UDVM instruction set? Also does 
>> anyone have any programming experience with the UDVM instruction set 
>> that can be shared?
>
>
> Does "the UDVM assembler/interpreter" refer to my half-baked 
> implementation of the -05 draft?
> I haven't got around to work on this implementation to upgrade it with 
> respect to the changes we made on the way to RFC3320 and the revised 
> assembler syntax we agreed on for the implementers guide.
>
>>  3. I tried out the examples posted by Carsten and these worked 
>> perfectly. However, can anyone tell me how we got the compressed 
>> message in the first place?
>
>
> A UDVM implementation is not a complete SigComp implementation.  In 
> addition you need:
> -- an interface to the higher layer protocol (e.g., SIP)
> -- a state manager
> -- a portfolio (>= 1) of compression algorithm implementations, and
> -- UDVM code to send to the decompressor for each of these.
>
> Clearly, these are significant pieces of work, some of which also have 
> interesting IPR complications.
>
> Gruesse, Carsten
>