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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