Re: ASN.1 Syntax of H.245

31 Aug 1999

      Mike,
I agree that this change has to be made.  The original form makes no sense
and, once pointed out, is clearly defective.
As you say, it will NOT affect the bits on the wire.  Indeed, depending on
the compiler you have, you can almost get away without changing any code you
have written (although re-compiling and tweaking would be advised).
Well spotted Jaakko and Paul.
Pete
=============================================
Pete Cordell
pete@tech-know-ware.com
=============================================
-----Original Message-----
From: mike.nilsson@BT.COM mike.nilsson@BT.COM
To: ITU-SG16@MAILBAG.INTEL.COM ITU-SG16@MAILBAG.INTEL.COM
Date: 31 August 1999 10:52
Subject: ASN.1 Syntax of H.245
...
An error has been found in the ASN.1 syntax of H.245 version 5. Thanks to
Jaakko Helanti and Paul Long for identifying it.
The error occurs in the section given below where the word 'OPTIONAL'
should
...
appear at the end of the line 'genericModeParameters    GenericCapability'.
This was an editorial error, but one that has some technical consequence.
Although the absence of the word 'OPTIONAL' does not change the
understanding of bits received by a decoder, it does demand that an encoder
always send the information 'genericModeParameters'. This was not the
intention and is not desirable.
ModeElement     ::= SEQUENCE
{
       type            CHOICE
       {
               nonStandard     NonStandardParameter,
               videoMode       VideoMode,
               audioMode       AudioMode,
               dataMode        DataMode,
               encryptionMode  EncryptionMode,
               ...,
               h235Mode        H235Mode
       },
   h223ModeParameters      H223ModeParameters OPTIONAL,
   ...,
   v76ModeParameters       V76ModeParameters OPTIONAL,
   h2250ModeParameters     H2250ModeParameters OPTIONAL,
   genericModeParameters   GenericCapability

}
I have contacted the ITU regarding this. Their response was that if there
is
...
consensus, as determined by e-mail, then as version 5 (05/99) of H.245 has
not yet been published, it will be possible to correct this error before
publication.
I hope that two weeks will be enough time for everyone to consider this
issue, and so aim to respond to the ITU on 13 September about whether we
have achieved consensus to make this correction.
Best regards
Mike Nilsson

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