Frequently Asked Questions

# Terms

## What does libambix stand for?

`libambix` is a library for reading and writing ambisonics exchange files.

## What is the difference between BASIC and EXTENDED ambix files?

`BASIC` ambix files contain exactly a full set of periphonic ambisonics channels, using ACN channel ordering and SN3D normalisation.

`EXTENDED` ambix files contain an additional adaptor matrix at the beginning of the file, which can be used to turn the actually stored audio channels into a full set of periphonic ambisonics channels (periphonic, ACN, SN3D). These files can be used to store a reduced number of channels (e.g. when your soundfield is horizontal only, there is no need to store the channels with height-information, as they will be muted anyhow), while providing a simple and standardized way to play them back on a full ambisonics decoder.

See The ambix format for more information.

# HOW-TOs

## How can I create an ambix file from a set of mono soundfiles?

If you have an ambisonics recording as multiple mono soundfiles following the ambix standard (channel ordering: ACN, normalisation: SN3D), you can merge them into an ambix files using the `ambix-interleave` command.

ambix-interleave -o ambixfile.caf recording-ambi0.wav recording-ambi1.wav recording-ambi2.wav recording-ambi3.wav

## How can I create an ambix file from a multichannel soundfile?

If you have an ambisonics recording already as a multichannel soundfile, with the channels following the ambix standard (channel ordering: ACN, normalisation: SN3D), you can create an ambix file from that using the `ambix-interleave` command.

ambix-interleave -o ambixfile.caf recording.wav

## How can I convert my .amb files to ambix?

You can use the `ambix-interleave` file to create EXTENDED ambix files from your old .amb recordings. If `ambix-interleave` detects that the input is an .amb file, it will add an adaptor matrix that converts from .amb's Furse-Malham channels to ambix channels, and will otherwise leave the audio data intact.

ambix-interleave -o ambixfile.caf recording.amb

## How can I convert my .amb files to ambix?

To create BASIC ambix files (without an adaptor matrix), you can use `ambix-deinterleave` to convert the .amb file to SN3D/ACN channels, and then use `ambix-interleave` to merge those files into a single ambix file:

ambix-deinterleave recording.amb
ambix-interleave -o ambixfile.caf recording-ambi*

## How can I convert an EXTENDED ambix file to BASIC?

The easiest way to convert an EXTENDED ambix file to a BASIC file is to first extract the channels into separate files using `ambix-deinterleave`, and then merge them back using `ambix-interleave`:

ambix-deinterleave ambixextended.caf
ambix-interleave -o ambixbasic.caf ambixextended-ambi*