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IMPACT: Iterative Mask-based Parallel Decoding for Text-to-Audio Generation with Diffusion Modeling
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Proposes IMPACT, which combines MAR-style iterative mask-based parallel decoding over continuous audio latents with a small MLP diffusion head and unconditional pre-training, achieving state-of-the-art FD/FAD on AudioCaps with lower latency than diffusion baselines.
Problem
Diffusion-based text-to-audio models (Tango, AudioLDM series) produce high fidelity audio but have high inference latency from slow diffusion sampling, while the discrete-token mask-based model MAGNET is fast but lags in audio quality.
Approach
Apply MAR-style iterative mask-based parallel decoding directly on continuous VAE audio latents, using a lightweight MLP diffusion head conditioned on a transformer latent encoder, plus an unconditional mask-modeling pre-training phase on unlabeled audio before text-conditional training.
Key results
- IMPACT base (5500h pre-train, 1200h text-cond, 64 decoding iterations) reaches FD 14.72 and FAD 1.13 on AudioCaps, versus EzAudio-XL FD 14.98 and Tango FAD 1.73.
- IMPACT base with 4 decoding iterations achieves FAD 2.85 and CLAP 0.321 versus MAGNET-S's FAD 3.22 and CLAP 0.287 at 50 decoding iterations.
- IMPACT base with 32 decoding iterations has latency 11.2 s for a batch of 8 on a V100, second only to MAGNET-S (6.9 s), and runs at 7.75 s for batch 64 vs MAGNET-S's 52.04 s.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| add unconditional pre-training (model a to model c) (ablation) | IMPACT base · AudioCaps evaluation set | FAD: 1.35 -> 1.13 | Helped |
| increase unconditional pre-training data from 1200 to 5500 hours (model b to model c) (ablation) | IMPACT base · AudioCaps evaluation set | REL: 4.15 -> 4.31 | Helped |
| increase text-conditional training data from 145 to 1200 hours (model d to model c) (ablation) | IMPACT base · AudioCaps evaluation set | FAD: 1.38 -> 1.13 | Helped |
| repeat text-conditional training on AudioCaps (model c to model c') (ablation) | IMPACT base · AudioCaps evaluation set | FD: 14.72 -> 13.86 | Helped |
| repeat text-conditional training on AudioCaps (model c to model c') (ablation) | IMPACT base · AudioCaps evaluation set | IS: 10.03 -> 9.41 | Hurt |
| remove the CLAP text encoder from model (c) (ablation) | IMPACT model (c) · AudioCaps evaluation set | FAD: 1.13 -> 1.13 | No clear effect |
| remove the CLAP text encoder from model (d) (ablation) | IMPACT model (d) · AudioCaps evaluation set | FAD: 1.38 -> 1.49 | Hurt |
| replace 32-iteration decoding with single-pass decoding (ablation) | IMPACT · AudioCaps evaluation set | FAD: 1.07 -> 12.26 | Hurt |
| reduce inference diffusion steps from 100 to 50 (ablation) | IMPACT model (b), dec iter 64 · AudioCaps evaluation set | FAD: 1.13 -> 1.57 | Hurt |
| increase inference diffusion steps from 100 to 150 (ablation) | IMPACT model (b), dec iter 64 · AudioCaps evaluation set | FAD: 1.13 -> 1.30 | Hurt |
| increase inference diffusion steps from 100 to 200 (ablation) | IMPACT model (b), dec iter 64 · AudioCaps evaluation set | latency: 22.2 -> 41.9 | Hurt |
| set maximum classifier-free guidance scale to 1.0 rather than 5.0 (ablation) | IMPACT model (c) · AudioCaps evaluation set | FAD: 1.13 -> 3.36 | Hurt |
Surprising findings
- A single-pass (non-iterative) variant performs far worse (FAD 12.26) than 32-iteration decoding (FAD 1.07), showing iterative decoding matters.
- Removing the CLAP text encoder leaves most metrics nearly unchanged, suggesting Flan-T5 embeddings alone suffice for text alignment.
Limitations
- Latency remains higher than MAGNET-S, the fastest baseline, at comparable batch sizes when using more decoding iterations.
- CLAP score lags Tango 2 and EzAudio, which are trained with DPO or data filtering.
- Random position selection replaces confidence-based selection since continuous latents have no confidence scores, and the paper provides no alternative analysis of its effect.
Experimental setup
Datasets: AudioSet AudioCaps WavCaps
Benchmarks: AudioCaps
Metrics: FD FAD KL IS CLAP REL OVL latency
Baselines: Tango Tango-full-ft Tango 2 AudioLDM2 EzAudio-L EzAudio-XL MAGNET-S MAGNET-L AudioGen v2 Make-an-Audio 2
Builds on: MAR MAGNET Latent diffusion models Classifier-free guidance AudioLDM
Closest papers by meaning
- Generative Audio Language Modeling with Continuous-valued Tokens and Masked Next-Token Prediction (ICML 2025 · similarity 0.89)
- Masked Audio Generation using a Single Non-Autoregressive Transformer (ICLR 2024 · similarity 0.88)
- Fast Timing-Conditioned Latent Audio Diffusion (ICML 2024 · similarity 0.88)
- MDSGen: Fast and Efficient Masked Diffusion Temporal-Aware Transformers for Open-Domain Sound Generation (ICLR 2025 · similarity 0.87)
- ETTA: Elucidating the Design Space of Text-to-Audio Models (ICML 2025 · similarity 0.87)
- AudioCALM: Continuous Autoregressive Language Modeling for Universal Audio Generation (NeurIPS 2026 · similarity 0.86)
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