The track information is stored in the description field of the bext chunk, and can also appear in the iXML chunk.
I’ve done a lot of research & testing on all this, as it’s a subject I teach at the UK Nation Film school Etc. . Here are some relevant (I hope) parts of notes i wrote.
A widely used and rather useful element in the Description field is TRK. Eg, a Sound Devices SD744T recorder can label each of its 4 tracks with info as to what is on each track & with say ProTools v7.2 or newer this can appear as a track label on each of the mono files it uses on the timeline – very handy.
In the Description Field the data will be written something like this:-
sTRK1= boom mic
sTRK2= Anna Rad Mic
sTRK3= Fred Rad mic
sTRK4= Delia Rad
Here are some more metadata examples
aTYP= (eg mono)
sSWVER= (Software Version)
… the Description & Coding history fields are not defined by the EBU who designed the BWF format nor the AES who ratified it.
What’s happened is manufacturers wanting to add extra info have developed a kind of de-facto, semi standard widely used but with variations. …
In an attempt to overcome the ambiguities of the use of the Description field in the bext chunk the IBS (Institute of Broadcast Sound) with a lot of input and co-operation from NLE & DAW manufacturers have come up with a new additional Wav Chunk using the increasingly common XML script language.
It’s potentially very extensive and is being adopted quite widely. Here is a partial list. Add http://www. to the addresses below for full URL’s to details of iXML implementations. …
… Because the bext chunk, iXML chunk and a session wrapper like OMFI can all carry the same types of information, there is the possibility that they have different values in them.
At the moment ProTools (Vers 7.2 or newer) sets the priority to:-
- OMF or MXF
BWF-Widget Pro will look for relevant data in the bext chunk if it’s not there then look at the iXML chunk. See the links at the end for more details …