Currently，the speech-driven 3D talking face generation technology has considerably matured，particularly with recent models based on vector quantized variational autoencoders （VQ-VAE），which achieve highly vivid facial expression generation by quantizing facial motion features. However，existing methods still suffer from limitations in facial reconstruction accuracy and emotional control stability. On the one hand，the facial detail reconstruction capability of VQ-VAE models requires further improvement. On the other hand，emotion guidance strategies in existing models remain relatively simplistic，failing to fully utilize multimodal information beyond speech，resulting in generated facial expressions that lack realism.

Inspired by the structures of conditional variational autoencoders and VQ-VAE-2，this study proposes the DecTalk3D model，a hierarchical decoupling method within the VQ-VAE framework. Facial features are decoupled into high-level and low-level features. Identity vectors and descriptive text are introduced as external conditions to decouple the high-level features. Afterward，the decoupled high-level features are used as internal conditions，working together with the two external conditions （identity vector and text） to further decouple the low-level features. This hierarchical decoupling mechanism aims to improve the facial reconstruction quality and the stability of emotional expression. During generation，speech and text information jointly guide facial generation in different ways： the text is encoded by the CLIP text encoder to leverage its rich semantic information for holistic expression control，while the speech is encoded by Wav2Vec 2.0 to precisely control lip movements and other subtle expressions. The model generates accurate facial motions by integrating multimodal information at different levels.

Experiments were conducted on the multi-view emotional audio-visual dataset（MEAD），3DMEAD and TA-MEAD datasets and included quantitative evaluation，visual analysis，and ablation studies. The proposed model was compared with FaceFormer，CodeTalker，FaceDiffuser，and ProbTalk3D. In terms of overall facial reconstruction accuracy，the proposed model achieved a 5.9% lower mean vertex error （MVE） than ProbTalk3D—which also incorporates emotional input—demonstrating that explicit emotion modeling effectively enhances geometric consistency and preserves facial structural accuracy，particularly for complex emotions. In terms of lip motion accuracy （LVE），the proposed model ranked second，with a 16.7% gap compared with the top-performing FaceDiffuser，while still outperforming FaceFormer and ProbTalk3D. The limited improvement may stem from the hierarchical decoupling approach，which，while decoupling emotional conditions，offers restricted decoupling for the mouth region，affecting detailed performance. In upper-face dynamic deviation （FDD），the proposed model significantly surpassed traditional methods even though it is inferior to ProbTalk3D，reflecting its ability to express emotional intensity. Moreover，the model showed notable advantages in distribution-based quality metrics： it achieved optimal mean estimation error （MEE） and coverage error （CE），with MEE 4.1% lower than ProbTalk3D and 58.4% lower than CodeTalker and CE 8.2% lower than ProbTalk3D and 61.6% lower than CodeTalker. This result indicated that hierarchical decoupling enhances distribution concentration and coverage of real samples，making generated facial motions close to real faces. However，the model had the lowest diversity score，highlighting a trade-off where hierarchical decoupling ensures semantic consistency but constrains variation—beneficial for emotion accuracy yet potentially limiting naturalness. Although traditional methods showed orders-of-magnitude differences in MVE and FDD due to lacking emotional input，and ProbTalk3D excelled in FDD and Diversity but lagged in accuracy，the proposed model balances high-precision reconstruction with superior distribution estimation through hierarchical decoupling and multimodal modeling.

Experimental results demonstrate that the proposed hierarchical decoupling-based method produces accurate and stable facial reconstructions，excelling in maintaining facial geometric consistency and expressing complex emotions. The model’s key innovation lies in its layered feature decoupling within the VQ-VAE framework，using identity vectors and text as external conditions and high-level features as an internal condition，which significantly enhances reconstruction quality and emotional controllability. This framework offers practical value for HCI，digital humans，and animation. Quantitative evaluation shows superior performance in MVE，LVE，and FDD，alongside stable MEE and CE scores，confirming the model’s ability to effectively integrate multimodal information for generating realistic expressions. Ablation studies validate the critical roles of the hierarchical feature decoupling and the synergy between internal and external conditions. However，limitations remain： generated lip movements are less pronounced compared with real speech，the current two-level feature decoupling is relatively simplistic，and the diversity and subtlety of emotional expressions require further improvement. Future work will focus on improving lip-sync quality，exploring finer-grained decoupling dimensions for differentiated guidance，and enhancing expression diversity while preserving accuracy. The source code is available on GitHub （https://github.com/chen114514sheng/DecTalk3D） and archived on ScienceDB （https://doi.org/10.57760/sciencedb.j00240.00095）.