5 min read
Poly WAV channel order: what track 1 actually is
Channel order is a convention, not a law. Knowing which convention your file follows prevents a whole class of post problems.
Inside a poly WAV, channels are simply numbered by their position in the interleaved stream. What each number means comes from the recorder configuration and the metadata, not from the format itself.
How recorders assign channels
Most field recorders map input 1 to channel 1 and so on, then append the stereo mix at the end. So an eight input bag with a mix produces channels 1 to 8 as isolated tracks and 9 and 10 as the mix.
Where the meaning is stored
- iXML track list: the recorder's own names for each channel.
- bext description: often a text summary listing tracks in order.
- The channel mask in the WAV extensible header, for surround layouts.
Surround order is not universal
Film convention is L, R, C, LFE, Ls, Rs. The SMPTE and ITU orders differ, and some game and broadcast tools expect L, R, Ls, Rs, C, LFE. Send a file with the wrong order and the dialogue in the centre ends up in a surround speaker.
Remapping without re-recording
A channel mapper reads the existing order, lets you reassign each output slot, and writes a new file. That is the fix when a delivery spec disagrees with what the recorder wrote, and it is lossless.
Verify before delivery
Inspect the file, confirm the channel count, layout and names, and audition each channel in isolation. Thirty seconds of checking beats a rejected deliverable.