DA-MLDGPerFail @ IEEE PerCom · 2023

On efficacy of Meta-Learning for Domain Generalization in Speech Emotion Recognition

Why emotion models struggle beyond their training domain

Raeshak King Gandhi Vasileios Tsouvalas Nirvana Meratnia

At a glance

An emotion model can fit one speech corpus and fail on another. DA-MLDG rehearses source-domain shifts during training and weights them with an energy-gap estimate. The study finds mixed generalization gains and exposes limits of the representations and benchmarks.

Learn across source domains
Source corporaMeta-trainingUnseen targetHeld out
01 / 05

Rehearse a domain shift

Source pool
ABC
Meta-train
ACS′
Meta-test
BV
Disjoint source subsets·Same training pool
Meta-train + Meta-test = Source domains
Source corporaMeta-trainingUnseen targetHeld out
02 / 05

One inner update

Meta-train
AC
θ
θ′
Inner stepθ′ = θ − η ∇Ltrain(θ)
Meta-train loss → Adapted parameters
Source corporaMeta-trainingUnseen targetHeld out
03 / 05

Energy gap → Shift weight

Meta-train · θ′
Etrain
|ΔE|Energy gapγ
Meta-test · θ′
Etest
Mean log-sum-exp→Meta-test weight
Adapted model · Two source energies · One weight
Source corporaMeta-trainingUnseen targetHeld out
04 / 05

Learn across the split

Meta-train
Ltrain(θ)
+
Meta-test
γ Ltest(θ′)
θ ← update
Update θ→Resample sources→Repeat
Weighted meta-test loss · Outer update · Repeat
Source corporaTraining completeUnseen targetEvaluate
05 / 05

Test an unseen corpus

Unseen corpus
Target
Trained model
θ*
Emotion prediction
Held-out evaluation
New corpus·Weights fixed at evaluation
Training complete · Target evaluation
Method diagram

Swipe across the diagram

What this adds

  • 01

    Domain-shift-aware meta-learning weights the loss on a held-out source subset using an energy gap.

  • 02

    Seven cross-corpus scenarios make both improvements and failure cases visible.

  • 03

    Representation analysis compares log-mel inputs with TRILLsson embeddings without claiming domain shift is solved.

Abstract

Speech Emotion Recognition (SER) refers to the recognition of human emotions from natural speech, vital for building human-centered context-aware intelligent systems. Here, domain shift, where models’ trained on one domain exhibit performance degradation when exposed to an unseen domain with different statistics, is a major limiting factor in SER applicability, as models have a strong dependence on speakers and languages characteristics used during training. Meta-Learning for Domain Generalization (MLDG) has shown great success in improving models’ generalization capacity and alleviate the domain shift problem in the vision domain; yet, its’ efficacy on SER remains largely unexplored. In this work, we propose a “domain-shift aware” MLDG approach to learn generalizable models across multiple domains in SER. Based on our extensive evaluation, we identify a number of pitfalls that contribute to poor models’ DG ability, and demonstrate that log-mel spectrograms representations lack distinct features required for MLDG in SER. We further explore the use of appropriate features to achieve DG in SER as to provide insides to future research directions for DG in SER.

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How it works

DA-MLDG

01

Simulate domain shifts within sources

Partition source domains into disjoint sets S′ and V at each iteration. A gradient step on S′ produces adapted parameters θ′.

θ′=θ−ηs∇θℒθ(S′)

§III, Eq. 2 and Algorithm 1. V is a source meta-test subset, not the final target test corpus.

02

Use energy as a shift proxy

Compute each subset’s average log-sum-exp of logits with θ′ and temperature 1. The absolute gap supplies γ, the adaptive weight.

γ=|E(S′,pθ′)−E(V,pθ′)|

Eq. 3, printed p. 423. The score is proposed as a proxy for domain shift, not a measured distance between speech distributions.

03

Optimize the weighted outer objective

Minimize source training loss plus γ times meta-test loss after adaptation. The outer optimization accounts for how θ′ depends on θ.

minθℒθ(S′)+γℒθ′(V)

Eq. 2. The formula presents the stated objective rather than Algorithm 1’s outer-update line, which omits an explicit gradient symbol.

04

Evaluate representation and transfer together

Compare ResNet-18 with log-mel inputs against a variant using TRILLsson embeddings. Seven source/target scenarios cover same-language and cross-language transfer.

Tables I, III and IV; ten trials per setting. The target corpora remain unseen during training.

Method details in the paper ↗

Original paper figures & sources
Audio from multiple source domains is converted into spectrograms and divided into meta-train and meta-test sets; an energy-based domain shift margin adjusts the meta-test contribution.Enlarge
Training repeatedly simulates a domain shift between source datasets. The estimated shift controls the influence of the meta-test loss when updating the shared emotion model. Figure 1 · PerFail paper, p. 423
Evaluation

Results

Cross-corpus emotion recognition

Log-mel inputs · seven scenarios · mean accuracy over ten trials

Generalization gains are uneven. Five-emotion SER with VoxCeleb-pretrained ResNet-18 and log-mel inputs; source and target corpora are defined in Table I. Mean target accuracy (%) over ten trials; higher is better. No dispersion is reported for these results.
Scenario · targetDeep-All (%)RSC (%)MLDG (%)DA-MLDG (%)
1 · IEMOCAP26.9532.3627.6131.35
2 · RAVDESS43.4044.7838.8639.41
3 · TESS47.0343.7746.2946.80
4 · CaFE43.1639.9742.5743.21
5 · AESDD60.6556.6960.4562.26
6 · ShEMO31.5440.7037.8738.79
7 · ShEMO40.1940.2734.5137.11

DA-MLDG leads in 2/7 scenarios; RSC leads in four.

Paper ↗

With pretrained speech embeddings

TRILLsson inputs · same seven scenarios · mean accuracy over ten trials

Target accuracy (%) ↑ Higher is better

Deep-AllDA-MLDG
1 · IEMOCAP
Deep-All: 28.57
DA-MLDG: 32.11
2 · RAVDESS
Deep-All: 42.61
DA-MLDG: 39.82
3 · TESS
Deep-All: 50.16
DA-MLDG: 48.46
4 · CaFE
Deep-All: 45.09
DA-MLDG: 43.29
5 · AESDD
Deep-All: 61.17
DA-MLDG: 64.11
6 · ShEMO
Deep-All: 33.16
DA-MLDG: 40.22
7 · ShEMO
Deep-All: 41.15
DA-MLDG: 36.97

With pretrained embeddings, DA-MLDG beats the supervised baseline in 3/7 scenarios.

Paper ↗
Reference

Cite this work

BibTeX
@inproceedings{gandhi2023damldg,
  author = {Gandhi, Raeshak King and Tsouvalas, Vasileios and Meratnia, Nirvana},
  title = {On efficacy of Meta-Learning for Domain Generalization in Speech Emotion Recognition},
  booktitle = {2023 IEEE International Conference on Pervasive Computing and Communications Workshops and other Affiliated Events (PerCom Workshops)},
  year = {2023},
  pages = {421--426},
  note = {PerFail 2023: Second International Workshop on Negative Results in Pervasive Computing},
  doi = {10.1109/PerComWorkshops56833.2023.10150265},
  url = {https://doi.org/10.1109/PerComWorkshops56833.2023.10150265}
}

Keep exploring

FedSER

Learn speech emotions from audio kept on each device

MaTU

Many local tasks. One shared task vector.

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