MH-LVC: Multi-Hypothesis Temporal Prediction for Learned Conditional Residual Video Coding

This work, termed MH-LVC, presents a multi-hypothesis temporal prediction scheme that employs long- and short-term reference frames in a conditional residual video coding framework. Recent temporal context mining approaches to conditional video coding offer superior coding performance. However, the need to store and access a large amount of implicit contextual information extracted from past decoded frames in decoding a video frame poses a challenge due to excessive memory access. Our MH-LVC overcomes this issue by storing multiple long- and short-term reference frames but limiting the number of reference frames used at a time for temporal prediction to two. Our decoded frame buffer management allows the encoder to flexibly utilize the long-term key frames to mitigate temporal cascading errors and the short-term reference frames to minimize prediction errors. Moreover, our buffering scheme enables the temporal prediction structure to be adapted to individual input videos. While this flexibility is common in traditional video codecs, it has not been fully explored for learned video codecs. Extensive experiments show that the proposed method outperforms VTM-17.0 under the low-delay B configuration in terms of PSNR-RGB across commonly used test datasets, and performs comparably to the state-of-the-art learned codecs (e.g.~DCVC-FM) while requiring less decoded frame buffer and similar decoding time.

Exploring Autoregressive Vision Foundation Models for Image Compression

This work presents the first attempt to repurpose vision foundation models (VFMs) as image codecs, aiming to explore their generation capability for low-rate image compression. VFMs are widely employed in both conditional and unconditional generation scenarios across diverse downstream tasks, e.g., physical AI applications. Many VFMs employ an encoder-decoder architecture similar to that of end-to-end learned image codecs and learn an autoregressive (AR) model to perform next-token prediction. To enable compression, we repurpose the AR model in VFM for entropy coding the next token based on previously coded tokens. This approach deviates from early semantic compression efforts that rely solely on conditional generation for reconstructing input images. Extensive experiments and analysis are conducted to compare VFM-based codec to current SOTA codecs optimized for distortion or perceptual quality. Notably, certain pre-trained, general-purpose VFMs demonstrate superior perceptual quality at extremely low bitrates compared to specialized learned image codecs. This finding paves the way for a promising research direction that leverages VFMs for low-rate, semantically rich image compression.