Add Ambisonic encoders/decoders from the IEM Plug-in Suite (StereoEncoder, BinauralDecoder, RoomEncoder, SimpleDecoder)

[RubenKelevra]

Hey guys!

Would be super cool if you could add these four plugins from the IEM Plug-in Suite to EasyEffects.

The plugins listed either encode or decode the Ambisonics surround sound format. The user would use them in pairs. The first filter would add the selected position information to their audio signal and output an Ambisonic audio signal.

The second filter reads the position info and the audio signal from the Ambisonics format and decodes it. For headphones, there's a decoder to create a binaural representation. For a speaker setup, there's a decoder which mixes it down to the available speakers and their positions in the room.

The benefit of this processing is, that the audio will sound like it's from the position selected while encoding, regardless where the speakers in the room are positioned or if the user just has a headphone on.

StereoEncoder

This plugin takes a regular stereo/mono audio signal and puts the sound into a position in a virtual space selected by the user. It can also process head tracking signals, to dynamically change the encoded direction according to the user's head position.

BinauralDecoder

The decoder takes the Ambisonic audio signals and converts the representation to a binaural audio signal. Binaural audio means, that audio signals are processed by their direction in a way our ears and head modifies audio signals from this direction.

As the Ambisonic encoder has encoded where the signal originates from, the BinauralDecoder has the positions for each audio-signal.

SimpleDecoder

The SimpleDecoder takes a configuration file (for example made by AllRADecoder out of this Suite) which defines the X/Y/Z positions of each speaker.

Ambisonic audio signals are then decoded for each of those speakers. In addition, a subwoofer channel can be defined if available.

RoomEncoder

The RoomEncoder plugin allows to not only position multiple mono audio sources in X/Y/Z positions in a virtual space (what the StereoEncoder does), but also define a room surrounding them. The plugin will then calculate the reflections inside the room, based on the user's listening position and the positions of the audio sources.

If the audio sources or the listening positions are moved, this plugin will also calculate the Doppler shift resulting from this (probably does not apply for this application).

[wwmm]

Interesting. I was not aware of this plugin suite. But the question is how many channels each plugin needs in the input/output. I am not familiar with the ambisonic encoding/decoding process but after a quick look at it I've got the impression it may need up to 64 channels in the input or output depending on whether the plugin is decoding or encoding. Is that right?

As EasyEffects uses a stereo pipeline it is not possible to handle plugins that require more than 2 channels. The only exception at this moment are the stereo plugins that have sidechain. As expected they have 2 extra channels for the sidechain input. But if we are talking about more than 2 audio channels in the pipeline the same problems we face for #1126 will apply here.

[deavid]

I would really like to have StereoEncoder integrated, even with basic parameters. The objective is to convert the input audio signal, to headphones emulating speakers.

If you're like me, that you listen mainly via headphones, music and a lot of games and apps do hard panning, where one of the speakers might not even sound.

One solution to this is to downmix to mono or to reduce the stereo image using the Stereo tools, however, StereoEncoder can emulate a basic room setting, which could preserve the majority of the stereo width without being unpleasant.

Also useful to make music and check how it sounds on speakers without actually having speakers; not that this could be trusted that much, but useful nonetheless.

[wwmm]

One solution to this is to downmix to mono or to reduce the stereo image using the Stereo tools, however, StereoEncoder can emulate a basic room setting, which could preserve the majority of the stereo width without being unpleasant.

The crossfeed plugin does something similar. It does not have room simulation but as far as reduce the stereo fatigue it is enough for me.

[deavid]

As far as I understand, it mixes down to mono the lowpass band. Not sure if it's enough. I was making the suggestion because of a friend who has this problem. I cannot tell that much.