CineMME: Benchmarking Fine-Grained Perception and Plot Reasoning in Multimodal Large Language Models

Cinematic understanding requires more than recognizing visible events: models must acquire dialogue evidence, bind it to speakers, and use it to infer narrative meaning. Existing video benchmarks evaluate pieces of this problem, including video question answering, audio-visual reasoning, and temporal grounding, but rarely test whether these abilities form a coherent cinematic evidence chain within the same clips. As a result, a model may answer a movie question correctly while failing to localize the relevant utterance, identify the speaker, or integrate speech with visual context. We introduce **CineMME**, a human-verified benchmark designed to diagnose speech-grounded cinematic reasoning, supported by approximately $1,600$ expert person-hours of annotation. CineMME contains $975$ curated movie clips and two linked tracks: *CineMME-Grounding*, with $13,554$ timestamped speech segments and $33,083$ actor face boxes for temporal dialogue localization, transcription, and active-speaker grounding; and *CineMME-Reasoning*, with $1,600$ multiple-choice and $316$ open-ended questions spanning perception, audio, narrative, social, and cinematic understanding. We evaluate $20$ MLLMs on reasoning and $10$ omni-modal models on grounding. The results reveal a pronounced who-what-when decoupling: Gemini-3 Pro localizes dialogue in time 68.33% tIoU) and partially transcribes it (WER 29.00%), yet reaches only 13.24% sIoU for active-speaker grounding while achieving 65.88% reasoning accuracy. Modality ablations further show that vision is not uniformly beneficial: it improves perception-heavy questions but can hurt dialogue-centric reasoning. CineMME provides a compact diagnostic testbed for measuring whether multimodal video models truly connect dialogue, speakers, visual evidence, and narrative meaning, rather than succeeding through disconnected cues.