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This paper addresses the underperformance of both open-source and commercial ASR systems on niche-domain Indic languages, specifically for entity recognition in code-mixed speech. They create a self-contained TTS-STT flywheel using an open-source Indic TTS pipeline to generate entity-dense synthetic data for fine-tuning Whisper models. The resulting LoRA fine-tuned models achieve substantial improvements in Entity-Hit-Rate (EHR) on Telugu, Hindi, and Tamil compared to existing systems, demonstrating the effectiveness of synthetic data for closing the ASR gap in low-resource languages.
Synthetic data closes the Indic ASR gap where commercial and open-source systems fail, boosting entity recognition by up to 22x.
Niche-domain Indic ASR -- digit strings, currency amounts, addresses, brand names, English/Indic codemix -- is under-served by both open-source SOTA and commercial systems. On a synthesised entity-dense Telugu test set (held-out by synthesis system), vasista22/whisper-telugu-large-v2 (open SOTA) achieves Entity-Hit-Rate (EHR) 0.027 and Deepgram Nova-3 (commercial) 0.16. We close this gap with a self-contained TTS<->STT flywheel: an open-source Indic TTS pipeline synthesises ~22,000 entity-dense Indic-English code-mix utterances at<$50 marginal cost, and a LoRA fine-tune on top of vasista22 achieves EHR 0.473 on the held-out test (17x over open SOTA, 3x over commercial), with read-prose regression bounded to +6.6 pp WER on FLEURS-Te. Cross-language: beta-Hi 0.337 (7x vs vasista22) and beta-Ta 0.543 (22x vs vasista22, 22x vs Deepgram); on Hindi where Deepgram has substantial entity coverage, the flywheel underperforms commercial. All three beta models fall below pre-registered EHR targets (0.75 for Te, 0.65 for Hi/Ta); we report honestly. A native-human-recorded sanity check (n=20 Telugu) confirms transfer to real speech (beta-Te EHR 0.516 on native vs 0.473 on synth). An EDSA-isolation ablation (LoRA on FLEURS-Te alone) yields EHR 0.020 on the same held-out, attributing ~100% of the gain to the EDSA corpus. We additionally report a language-conditional finding: vanilla Whisper-large-v3 has Telugu-specific Script Collapse (SFR 0.46-0.71) that a per-language LoRA corrects (SFR 0.81-0.97), but the recipe is contraindicated on Hindi and Tamil where vanilla SFR>= 0.98. Code, holdouts, predictions, EDSA corpus, and entity dictionaries are released open-source.
