Wireshark-bugs: [Wireshark-bugs] [Bug 6009] New: H323 rate multiplier wrong

Date: Thu, 9 Jun 2011 01:25:09 -0700 (PDT)

           Summary: H323 rate multiplier wrong
           Product: Wireshark
           Version: 1.5.x (Experimental)
          Platform: Other
        OS/Version: Windows 7
            Status: NEW
          Severity: Normal
          Priority: Low
         Component: Wireshark
        AssignedTo: wireshark-bugs@xxxxxxxxxxxxx
        ReportedBy: johnreg@xxxxxxxxx

Build Information:
Version 1.5.0-SVN-35142 (SVN Rev 35142 from /trunk
When looking at H323 traces the rate multiplier is incorrect by 128 so if I
place a call at 1920 kbps this should be a rate multiplier of 30 (30 x 64 Kbps)
but in wireshark it is decoded as 158 so and extra 128 is added.

An example is shown here (call rate 1920, rate multiplier should be 30)

...1 1000 = Information transfer rate: Multirate (64 kbit/s base rate) (0x18)
Rate multiplier: 158

Looking at the H225 spec only bits 1-7 should be used for the rate multiplier,
bit 8 is always set to 1.

"Rate multiplier (octet No. 4.1) 
– Shall be present if information transfer rate is set to "multirate". 

– The extension bit (bit 8) shall be set to "1". 

– The bits 1 through 7 shall indicate the bandwidth needed for the call as
defined in the following (note, that in contrast to ITU-T Rec. Q.931, a  value
of "0000001" is allowed here)."

Think this is the case in current release as well.

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