1     Function 2     Reference Model 3     Input/Output Data
4     SubAIMs 5     JSON Metadata 6     Profiles
7     Reference Software 8     Conformance Texting 9     Performance Assessment

1     Functions

Audio Analysis Transform (CAE-AAT):

Receives Audio Object  As Multichannel Audio
Transforms Multichannel Audio into frequency bands via a Fast Fourier Transform (FFT). The following operations are carried out in discrete frequency bands. When such a configuration is used, a 50% overlap between subsequent audio blocks needs to be employed. The output is a data structure comprising complex valued audio samples in the frequency domain.
Produces Audio Object In the Transform domain.

2     Reference Model

Figure 1 depicts the Reference Architecture of the Audio Analysis Transform (CAE-AAT) AIM.

Figure 1 – Audio Analysis Transform (CAE-AAT) AIM

3    Input/Output Data

Table 1 specifies the Input and Output Data of the Audio Analysis Transform (CAE-AAT) AIM.

Table 1 – Audio Analysis Transform (CAE-AAT) AIM

Input Description
Audio Object Audio Object (with associated Microphone Array info)
Output Description
Audio Object (Transform) The result of the application of the Fast Fourier Transform to Multichannel Audio.

4     SubAIMs

No SubAIMs.

5     JSON Metadata

https://schemas.mpai.community/CAE1/V2.3/AIMs/AudioAnalysisTransform.json

6     Profiles

No Profiles

7     Reference Software

8     Conformance Testing

The following steps shall be followed when testing the Conformance of  a CAE-AAT AIM instance.

  1. Use the following datasets:
    1. DS1: n Test Audio Object files including Multichannel Audio as Interleaved Multichannel Audio format.
    2. DS2: n Expected Audio Object Output files including data in Transform Interleaved Multichannel Audio format.
  2. Feed the AIM under test with the Test files (DS1).
  3. Perform the following steps to analyse the Audio Object (Transform) with the Expected Audio Objects (DS2):
    1. Check the data format of the Audio Object (Transform) with the format of the given Expected Audio Objects.
    2. Calculate the peak-to-peak Amplitude (A) of each Audio block in the Expected Audio Objects.
    3. Calculate the RMSE of each Audio block by comparing the Audio Object (Transform) (x) with the Expected Audio Objects  (y).
    4. Accept the AIM under test if, for each audio block, these two conditions are satisfied:
      1. Data format of the Audio Object (Transform) is the same as the format  of the Expected Audio Object and
      2. RMSE < A* 0.1%.
  4. The Conformance Tester will provide the following matrix containing a limited number of input records (n) with the corresponding outputs. If an input record fails, the tester would specify the reason why the test case fails.
Input data (DS1) Expected Output Data (DS2) Data Format RMSE
Audio Object (Microphone Array) ID1 Audio Object (Transform) ID1 T/F < A*0.1%
Audio Object (Microphone Array) ID2 Audio Object (Transform) ID2 T/F < A*0.1%
Audio Object (Microphone Array) ID3 Audio Object (Transform) ID3 T/F < A*0.1%
… … … …
Audio Object (Microphone Array) IDn Audio Object (Transform) IDn T/F < A*0.1%
  1. Final evaluation: T/F Denoting with i, the record number in DS1 and DS2, the matrices reflect the results obtained with input records i with the corresponding outputs i.
DS1 DS2 Audio Object (Transform) output value (from AIM under test)
DS1[i] DS2[i] Audio Object (Transform)[i]

Table 2 provides the Conformance Testing Method for the formats of the CAE-AAT AIM output.

Note: If a schema contains references to other schemas, conformance of data for the primary schema implies that any data referencing a secondary schema shall also validate against the relevant schema, if present and conform with the Qualifier, if present.

Table 2 – Conformance Testing Method for CAE-AAT AIM

Receives Audio Object (Microphone Array) Shall validate against Audio Object schema.
Audio Data shall conform with Audio Qualifier.
Produces Audio Object (Transform) Shall validate against Audio Object schema.
Audio Data shall conform with Audio Qualifier.

9     Performance Assessment