[Openh323-devel] Bug in ASNParser causing Interop issue

[Simon H. <s....@is...>]

Working with the guys from Tandberg I think we have discovered a bug in the 
ASNParser for OpenH323/Opal which shows itself with H.261 video

ASN1 code
H261VideoCapability     ::=SEQUENCE
{
         qcifMPI         INTEGER (1..4) OPTIONAL, -- units 1/29.97 Hz
         cifMPI          INTEGER (1..4) OPTIONAL, -- units 1/29.97 Hz
         temporalSpatialTradeOffCapability       BOOLEAN,
         maxBitRate      INTEGER (1..19200),       -- units of
                                                    -- 100 bit/s
         stillImageTransmission  BOOLEAN,           -- Annex D/H.261
         ..., 
<--- Everything after this technically is receive optional send mandatory
         videoBadMBsCap  BOOLEAN
}

Tandberg equipment does not send the videoBadMBsCaps field which 
OpenH323/Opal treats as mandatory hence rejects the OLC. This problem 
arises from a difference in interpretation of the ASN.1 For correct 
backwards inter operability behaviour is to treat everything after "...," 
as receive optional but send mandatory however OpenH323/Opal incorrectly 
treats all these fields as mandatory.

I think we need to look at the ASNParser to correct this behaviour

Simon