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

Date: Fri, 03 Jun 2016 10:36:47 +0000

Comment # 4 on bug 12490 from
Anders,

It is Simple Video Format

0x00 - 61883/IIDC
0x01 - MMA over AVTP
0x02 - Simple Audio Format
0x03 - Simple Video Format

0x02 and 0x03 are referenced in 1722A.  I see from packet-ieee1722a.c that only
the audio types are dissected currently.  Hence the problem I am seeing, so not
a bug but intention.

Another point is that the standard publication seems to be in limbo.  The
previous version is superseded but the current draft is not released.

I guess this ticket should be parked until the latest spec is released then
this can be a feature request at some point.

Paul


(In reply to Anders Broman from comment #3)
> (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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