Every professional WAV file carries metadata, information embedded in the file header that describes the recording. The two standard metadata formats for broadcast and production audio are bEXT (Broadcast Wave Extension) and iXML. If your WAV files have incorrect, incomplete, or missing metadata, this article explains how to fix it without touching the audio.
What is bEXT metadata?
bEXT stands for Broadcast Wave Extension. It's a chunk of data added to WAV files by the European Broadcasting Union to carry production metadata. Fields include:
- Description (a free text note)
- Originator (usually the recorder manufacturer or software)
- Originator Reference (a unique identifier)
- Origination Date and Time
- Timecode (BWF Timecode Reference)
What is iXML metadata?
iXML is a more detailed metadata format stored as XML inside the WAV file. It's used by professional field recorders and post-production systems. iXML fields include:
- Project name
- Scene number
- Take number
- Track names and track functions (one per channel)
- Notes and user info
- Circled and wild take flags
- File set information, which is how separate mono files are known to belong to one take
Most professional field recorders write both bEXT and iXML into every recorded file.
When metadata is wrong or missing
Incorrect metadata causes problems downstream. Editors and DAW systems use scene and take information to auto-conform audio to picture. If the scene number is wrong, the audio lands in the wrong place. If track names are missing, the editor can't tell which channel is the boom and which is the lav.
Editing bEXT and iXML with Wave Copilot
Wave Copilot reads and writes both formats in one editor, laid out over five tabs: General for project, scene, take, notes and the circled and wild flags; Recording for sample rate, frame rate, start timecode and user bits; Track Info for the per-channel names and functions; History for what the recorder wrote about itself; and Cues for the sync points inside the file. Nothing here re-encodes the audio. The metadata is rewritten and the samples are left exactly as they were.
Select several files and an edit applies to all of them at once, which is what makes a day's worth of corrections a single operation:
- Correcting a scene number across an entire shooting day
- Adding a project name to files that were recorded without one
- Setting track names to match the production's naming convention
- Flagging the circled takes before the report goes out
Two things stay per-file on purpose. Start timecode is one, since a batch of takes never shares a start time, and cue points are the other. Both are edited on a single selected file.
Getting the timecode right
Timecode is not a free text field, and the Recording tab treats it as the pair of values it really is. Start TC is the human-readable view; Samples Since Midnight is the number the file actually stores. Change one and the other follows.
Two checkboxes decide what happens when the format changes underneath it. Preserve Start TC, on by default, holds the displayed timecode when you change sample rate or frame rate and recalculates the stored sample count to match, which is what keeps a take in sync with the camera. Turn it off only when you want the opposite. Use Originator Time sets Start TC from the recorder's own time-of-day stamp, for files that were written with a clock but no usable timecode.
And when a jam sync failed altogether, retyping timecode is not the fix. If a timecode generator was recorded onto a track as audio, which is the usual fallback on a rig with no timecode-capable transmitter, the Audio TC tab decodes that burst and writes it into the file as real BWF timecode, sample-accurate rather than rounded to the nearest frame, into both the bEXT chunk and iXML. It can mute the burst on the way out too, on the channels that carry it and nowhere else, writing muted copies so your originals are never modified. After that the file behaves like any recorder file: it conforms, it reports, and it lines up in an NLE.
Conclusion
Maintaining clean, accurate metadata in your WAV files saves significant time in post-production and reduces the risk of sync errors. Wave Copilot's free 14-day trial, for Windows, macOS and Linux, is a good place to start if your metadata workflow needs improvement.