ambisonictoolkit/atk-kernels

A set of impulse response files used for convolution-based encoders and decoders

ambisonictoolkit

atk-kernels's Issues

NFC radius for CIPIC binaural decoders?

Current code lists the NFC filtering: r = 1.95

Need to check if this is correct, or not!

README

Update README to include more details on the various kernels.

Include Optimised RIRs

See:

• Integrate Isophonics Room Impulse Response Data Set
• Support RIR encoding
• Reaper ATK screencast : Encode mono - part II (Advanced)

FOA spherical decoder kernels are silent at 176.4 and 192kHz

Marco Del Piano reports that the spherical 192000 files don’t work, the files are silent. Investigating, it seems like the new 176.4 kHz kernels for the spherical decoder has the same problem too.

The new kernels for encoders at 176.4 kHz looks good, this only seems to be an issue with the binaural decoders.

Center "look" of measured HRTF binaural decoders

The binaural decoders generated from measured HRTFs (Listen, CIPIC) currently encode without regard to the individual subject's "look direction". That is, it is assumed each subject is looking at [0, 0] during measurement. In practice, the true look direction varies somewhat with each subject.

Measuring the (band-limited, "pinked") normalized intensity vector will give a reasonable measure of the true "look" of each subject.

Correcting for "look" will bring greater consistency to measured binaural decoders.

Support / integration for YouTube / Jump Inspector?

@henk-spook questioned whether the binaural kernels can be used with Google's YouTube / Jump Inspector

https://storage.googleapis.com/jump-inspector/workflow/thrive.zip

Would be useful to find out what, if any, changes would be necessary to do so.

They are using AmbiX1 encoding (ACN-SN3D), and I recall seeing something that looked like a virtual speaker cube decoding strategy.

There are a few strategies I can think of:

• supply a new set of HRTFs in the form Jump Inspector requires
• request Jump Inspector support "harmonic style" decoding

The first of these would require generating new sets from the current ATK sets. Results would maintain all the desired qualities of ATK criteria.

The second is more efficient in terms of processing, and the current Jump Inspector developers may not be aware of this technique.

Realtime optimized encoding/decoding kernels

The current encoding and decoding kernels are linear phase, meaning they sound great ;), but as such there is a delay in the signal, which may not be ideal in some live situations. This issue is to make note of the discussion we've had about minimum phase or "mixed phase" filters which would minimize the delay. This implies a good amount of research and experimentation!

Just getting the thread going...

Installation folder name conflict

The release for kernels comes in a folder with the release number appended and "atk-" prepended. E.g.,

atk-kernels-1.1.0

atk-sc3 expects the kernel folder to just be named

kernels

As a result, dropping the unzipped and un-renamed folder into Platform.userExtensionDir does not result in a working atk-sc3 installation. Here's my reply on the sc-users list to a new user attempting an installation.

The question, then, is what is the best way to resolve? Do we just give atk-sc3 users an instruction to rename the folder as I've done here (follow to my reply at the bottom)?

We'd like atk-sc3 and atk-reaper to both use the same assets to keep everything synchronized.

Related atk-sounds issue: Installation folder name conflict #3

Externalise binaural decoders

Add externalisation to binaural decoders.

Question: Should the current HRTFs be replaced with the externalised versions? Or, should these be added as a new set.

Git Large File Storage (LFS)

README.md includes a section discussing Git LFS:

Working with this repository

The sound files in this repository are versioned using Git Large File Storage (LFS). You will need to install LFS in order to clone and work on this repository. The repository is set up to use LFS with all WAV files.

Is this up to date? If not, I'd expect the Working with this repository section should be modified or removed.

Measured binaural decoders in all supported SRs

Currently, the measured binaural decoders are available only at SR = 44.1kHz. This reflects the SR of the original HRTF measurements. (CIPIC, Listen)

Ideally, binaural decoders should be made available in all supported SRs.

NOTE: The Spherical Head model HRTFs are available in all supported SRs.

Personalized HRTF support / SOFA/AES69

Responding to this question at atk-reaper:

SOFA/AES-69 import for binaural decoder? #43

Two commercial products include support for import of personalized HRTFs from SOFA/AES69 files:

• BlueRipple's Rapture3D Advanced
• NoiseMaker's Ambi Head

BlueRipple describes the support as "experimental".

For ATK support, we'd either want to release a decoder design routine as a utility, or set up an online SOFA-file upload / ATK-decoder-kernel download mechanism...

Add kernel support for 176.4 Hz

This is one of the sample rates offered by most hi end audio cards as well as Reaper, and although it is probably less used than 196 kHz, one might imagine someone using it for oversampled processing targeting CD production (the sample rate is 4 x 44.1 kHz).

This issue relates to #1 .