5 min read
Why professional recorders write poly WAV by default
It is not a legacy quirk. Poly is the safest thing a recorder can write while cameras roll and cards fill.
Every serious field recorder offers mono, poly or both, and nearly every one ships with poly selected. The reasoning is about what can go wrong between the microphone and the transfer drive.
Fewer files, fewer failures
A 16 track day in mono is sixteen file handles open per take and sixteen files to flush on stop. In poly it is one. Less filesystem churn means fewer chances of a truncated file when a battery dies mid take.
Metadata written once
Scene, take, circled status, notes and track names live in the iXML and bext chunks. In poly they are written once and describe the whole take. In mono they are duplicated across files that can drift apart if someone renames one of them.
Guaranteed channel alignment
Interleaved channels cannot slip relative to each other. There is no scenario where track 5 starts a frame late, because the samples share the same data chunk.
Card management on set
- A take is one object to copy, verify and checksum.
- Sound reports map one to one with files.
- Nothing is lost when a mono file is accidentally left behind in a transfer.
The trade off lands in post
The cost is that someone has to split the file later. That is a deliberate trade: complexity moves from the set, where mistakes are unrecoverable, to the transfer bay, where they are not.