Dialogue Editing

Metadata Demystifi ed 77
pipeline, but now it’s largely computerized, which makes it much scarier.
(And, of course, there are fewer people on the payroll to sort out the information
so there’s more pressure on the survivors.)
Broadcast Wave Format
Making all of this data management possible are rich soundfi le formats, such
as the increasingly standard Broadcast Wave Format (BWF) fi les, which carry
more than just sound, including timestamps and scene/shot/take and all
sorts of other information. BWF, an enhancement of the familiar WAVE (.wav)
fi le, has quickly become an industry favorite. Since the prime reasons for
creating it were interchangeability between platforms and ease in managing
multichannel recordings, BWF has been widely adopted in audio production
and post.
Microsoft WAVE fi les are made up of components called chunks, that is, blocks
of data containing specifi c types of information with the largest chunk containing
the audio data. Each chunk has an identifi cation fi eld and a size
indicator so that any number of machines can read the fi le, address what they
can cope with, and disregard the rest. This helps to make this format more
universal than those that aren’t compartmentalized because it allows numerous
manufacturers to develop applications for similar tasks without having
to completely rewrite their source code.
Start with a linear PCM WAVE fi le (not all WAVE fi les are linear PCM), add
a broadcast extension chunk, and you have a BWF fi le, 10 as shown in Table
5-2. The information in the broadcast extension chunk is standardized enough
to be readable on many platforms, yet fl exible enough to be useful in fi lm
and television production, TV and radio broadcasting, multimedia and games,
and other applications.
The Impact of Disk-Recorded Files
Many vintage Avids can’t accept fi les with word lengths greater than 16 bits,
so once the picture is edited there must be a way to replace the edited 16-bit
soundfi les with their 24-bit parents. By using a metadata management
10 A thorough description of the BWF format can be found in “The Broadcast Wave
Format—An Introduction” by Richard Chalmers of the EBU Technical Department, in
EBU Technical Review (Fall 1997). Also see “BWF—A Format for Audio Data Files in Broad -
casting,” EBU Technical Specifi cation (June 2001); and “Broadcast Wave Format (BWF) User
Guide,” a publication of the European Broadcasting Union (http://www.ebu.ch/en/technical/
publications/userguides/bwf_user_guide.php).