Do Modern Video-LLMs Need to Listen? A Benchmark Audit and Scalable Remedy

Abstract

Speech and audio encoders developed over years of community effort are routinely excluded from video understanding pipelines -- not because they fail, but because benchmarks never required listening. We audit 10 video benchmarks and find items largely solvable from visual cues alone: a single-frame probe answers ~77% of AVQA without audio, suggesting poor measurement of audio-visual reasoning. Building on LLaVA-OneVision, we attach a speech/audio encoder and compare five compressor architectures under 25x token reduction (25 Hz to 1 Hz). Across 10 benchmarks -- with and without filtering -- audio yields clear gains on tasks requiring speech comprehension or cross-modal grounding, while vision-centric suites remain largely unaffected. Our results show that speech encoders play a larger role in video understanding than current benchmarks suggest. We will fully open-source our work at https://github.com/naver-ai/LLaVA-AV-SSM.