Smac
Global Narrative Harmony
Measures agreement in narrative content, entity identity, environment, and affective tone across the entire clip.
1 Zhejiang University · 2 HiThink Research · 3 Fudan University · 4 Lanzhou University
As joint audio-video generation models become more capable, they can generate audio-visual scenes exhibiting three forms of complexity: multi-event composition, multi-layer audio mixture, and asymmetric cross-modal relations. However, current evaluations largely reuse metrics from earlier simple and unidirectional tasks. They typically evaluate an audio-video clip as a whole and rely on simple predefined relations, making them unsuitable for these increasingly complex scenes. We propose an event-centric evaluation framework that disentangles audio and visual events at the event level, analyzes each event independently, cross-validates relations across modalities, and aggregates the judgments into a coarse-to-fine, three-level consistency metric. The metric assesses global narrative harmony, event-level temporal synchronization, and fine-grained attribute alignment, providing a general formulation for audio-video consistency evaluation across diverse generation settings and cross-modal relations. We instantiate the metric as AVC-Reward, a trainable audio-video reward model. To evaluate the agreement between automatic judgments and human perception across generation paradigms and relation complexities, we construct AVC-Benchmark, which is primarily built from diverse positive and negative samples generated by various types of audio-video generation models. AVC-Reward achieves state-of-the-art alignment with human judgment among automatic methods, provides interpretable rationales that localize failures, and improves the audio-video consistency of a joint generation model when used as an online reinforcement-learning signal.
Overview
Modern joint audio-video generation introduces multi-event composition, multi-layer audio mixtures, and asymmetric cross-modal relations, challenging existing clip-level and predefined-relation metrics. We propose an event-centric framework that disentangles individual events, distinguishes audio source roles, and cross-validates event-dependent relations across modalities, yielding a coarse-to-fine, three-level consistency metric.
Smac
Measures agreement in narrative content, entity identity, environment, and affective tone across the entire clip.
Stemp
Evaluates event presence and temporal alignment of onset, offset, and duration under event-dependent cross-modal relations.
Sattr
Assesses physical, morphological, and causal-response compatibility within temporally verified event relations.
SAVC=(Smac + Stemp + Sattr) / 3
Method
AVC-Reward implements the three-level metric through five-stage structured reasoning. Audio-only and video-only analyses extract global descriptions and individual events; bidirectional verification establishes their cross-modal relations and supporting evidence. The final stage computes Smac from global descriptions, and Stemp and Sattr from verified event relations. The three scores lie in [0, 1], with their arithmetic mean SAVC serving as the overall reward.
Structured reasoning data supports SFT cold start, while human-calibrated scores are used for GRPO alignment. The overall score, SAVC, also serves as the online reinforcement-learning reward for LTX-2.
Results
AVC-Benchmark: 706 samples. Primary metrics: Δ-Pairwise (Δ > 0.2) and PLCC.
On AVC-Benchmark (706 samples), AVC-Reward achieves the strongest human alignment among automatic methods (0.728 Δ-Pairwise; 0.494 PLCC). As human-score differences become clearer, its pairwise accuracy improves and approaches the human upper bound, reflecting a judgment pattern more closely aligned with human perception.
Replacing DeSync with SAVC as the OmniNFT reward improves audio-video consistency across three benchmark prompt sets: AV-Phys-Bench, VABench-T2AV, and AVGenBench. Consistent improvements on external consistency metrics demonstrate the effectiveness of AVC-Reward as an optimization signal.
Examples
01 · Reward-model examples
The three score columns and conclusion are AVC-Reward outputs. The overall score combines its three dimensions; the human average is shown for reference.
| Case | Macro-semantic | Temporal | Fine-grained | Overall / conclusion |
|---|
02 · Generated examples
Each row uses the same prompt for three audio-video generations: LTX-2, OmniNFT, and Ours (AVC-Reward).
| Prompt (abbreviated) | LTX-2 | OmniNFT | Ours |
|---|
03 · Additional generated cases
Each row uses the same prompt for three audio-video generations: LTX-2, OmniNFT, and Ours (AVC-Reward).
| Prompt (abbreviated) | LTX-2 | OmniNFT | Ours |
|---|