Wireshark-bugs: [Wireshark-bugs] [Bug 12490] Incorrect decode of 1394 dissection as part of 1722

Date: Fri, 03 Jun 2016 08:29:02 +0000

Comment # 3 on bug 12490 from
(In reply to Paul from comment #2)
> Alexis,
> 
> I'm far from an expert either but I did buy the spec.  Unfortunately it's
> not so enlightening either.  Apart from the comment that 00 represents no
> CIP header it does not include an example of this.  I haven't been able to
> find any examples either.  I do have some sample code that reconstructs the
> camera data so I am reverse engineering that at the moment to find out what
> should be going on.  It certainly looks like the the data payload commences
> immediately after the 1394 header without the CIP header.  I haven't yet
> decoded the payload (rebuild a jpg image) but as soon as I have done that I
> will be able to confirm for sure the correct dissection.  I will post an
> update as soon as I get the definitive information.
> (In reply to Alexis La Goutte from comment #1)
> > Hi Paul,
> > 
> > Can you explain the "good" dissection needed ? (i no a expert on 1722
> > stuff... and the spec are not available...
This link
http://avnu.org/wp-content/uploads/2014/05/AVnu-AAA2C_Audio-Video-Transport-Protocol-AVTP_Dave-Olsen.pdf

Has some pictures of the header layout
What does the standard say about the subtype field, the link only gives:

AVTP subtype field specifies streaming protocol

00     61883_IIDC     IEC    61883/IIDC    over    AVTP
01     MMA     MMA    payload    over    AVTP    
:
e.g 3 is not listed

Regards
Anders


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