Opening Files

Ways to open a file

• Open Ambisonic WAV… on the welcome screen's Ambisonics card, Open file… in the footer, or File ▸ Open… (⌘O).
• Drag a WAV onto the window. One file opens it; several files dropped on the welcome screen's Batch card start a batch.
• In Finder, Open With ▸ Aro, or drop a file on Aro's Dock icon.
• File ▸ Open Recent.

Opening another file stops the one that's playing.

What Aro reads

Aro reads multichannel WAVs of Ambisonic order 1 to 7:

Order	Channels
1	4
2	9
3	16
4	25
5	36
6	49
7	64

It also opens Mid-Side, Double Mid-Side and A-format recordings. See Mid-Side & A-format.

Once a file is open, the file chip in the top bar shows its name over a short info line, such as 3OA · 16 ch · 48 kHz.

Channel format

Ambisonic files come in different channel orders and normalisations, and a plain WAV doesn't record which one it uses. Choose it in Configuration ▸ Format:

• AmbiX (ACN channel order, SN3D normalisation) — the default, and what most tools and libraries use today.
• N3D — ACN order with N3D normalisation.
• FuMa — the older B-format convention, up to 3rd order. FuMa itself stops at 3rd order, so a higher-order file set to FuMa is refused: "FuMa is defined up to 3rd order. Choose AmbiX or N3D."

A file that says it's FuMa (a .amb file, or a WAV carrying the B-format marker) opens as FuMa, and the Format section reads Read from the file: FuMa. You can still choose another. To change what a plain WAV opens as, set Preferences ▸ Decode ▸ Format when a file doesn't say.

Changing the format reads the file again. If it's playing, playback carries on after a short gap.

"What is this file?"

Some channel counts could mean more than one thing. A 4-channel file could be first-order Ambisonics or an A-format recording; a 2-channel file could be Mid-Side. Aro never decides for you. It shows What is this file?, lists what the file could be with a Suggested choice first and a plain reason for each, and lets you pick. Aro suggests; you decide.

A one-channel file is treated as one microphone of a recording kept as separate files: Aro asks which recording it belongs to, opens it, and you add the others. See Combining Files.

Sample rate

A device plays one rate at a time. When a file's sample rate differs from your output device's, Aro shows This file's sample rate and asks:

• Change the device to the file's rate. Nothing is converted, but other apps using the device switch too.
• Convert to the device's rate. Your device stays as it is and Aro converts the file as it plays. A decode still writes the file's own rate unless you choose another.

Press 1 or 2 to choose. Turn on Remember my choice to stop being asked, and change it later in Preferences ▸ Monitoring. Aro puts the device back to its own rate when the file closes and when you quit.

Files Aro refuses

Aro says why in plain words. For example:

• A channel count that isn't an Ambisonic order, such as 20 channels: "20 channels is not an Ambisonic order".
• Orders above 7th (more than 64 channels).
• A plain stereo mix. If it's really a Mid-Side recording, choose Mid-Side.