A easy vision-encoder text-decoder structure for multimodal duties – Google AI Weblog

Imaginative and prescient-language foundational fashions are constructed on the premise of a single pre-training adopted by subsequent adaptation to a number of downstream duties. Two primary and disjoint coaching situations are well-liked: a CLIP-style contrastive studying and next-token prediction. Contrastive studying trains the mannequin to foretell if image-text pairs appropriately match, successfully constructing visible and textual content representations for the corresponding picture and textual content inputs, whereas next-token prediction predicts the more than likely subsequent textual content token in a sequence, thus studying to generate textual content, in line with the required job. Contrastive studying permits image-text and text-image retrieval duties, akin to discovering the picture that greatest matches a sure description, and next-token studying permits text-generative duties, akin to Picture Captioning and Visible Query Answering (VQA). Whereas each approaches have demonstrated highly effective outcomes, when a mannequin is pre-trained contrastively, it sometimes doesn’t fare nicely on text-generative duties and vice-versa. Moreover, adaptation to different duties is commonly completed with advanced or inefficient strategies. For instance, with a view to lengthen a vision-language mannequin to movies, some fashions must do inference for every video body individually. This limits the scale of the movies that may be processed to just a few frames and doesn’t totally reap the benefits of movement data accessible throughout frames.

Motivated by this, we current “A Easy Structure for Joint Studying for MultiModal Duties”, referred to as MaMMUT, which is ready to practice collectively for these competing goals and which offers a basis for a lot of vision-language duties both straight or through easy adaptation. MaMMUT is a compact, 2B-parameter multimodal mannequin that trains throughout contrastive, textual content generative, and localization-aware goals. It consists of a single picture encoder and a textual content decoder, which permits for a direct reuse of each elements. Moreover, an easy adaptation to video-text duties requires solely utilizing the picture encoder as soon as and might deal with many extra frames than prior work. Consistent with current language fashions (e.g., PaLM, GLaM, GPT3), our structure makes use of a decoder-only textual content mannequin and could be regarded as a easy extension of language fashions. Whereas modest in measurement, our mannequin outperforms the cutting-edge or achieves aggressive efficiency on image-text and text-image retrieval, video query answering (VideoQA), video captioning, open-vocabulary detection, and VQA.

The MaMMUT mannequin permits a variety of duties akin to image-text/text-image retrieval (prime left and prime proper), VQA (center left), open-vocabulary detection (center proper), and VideoQA (backside).

Decoder-only mannequin structure

One shocking discovering is {that a} single language-decoder is adequate for all these duties, which obviates the necessity for each advanced constructs and coaching procedures offered earlier than. For instance, our mannequin (offered to the left within the determine beneath) consists of a single visible encoder and single text-decoder, related through cross consideration, and trains concurrently on each contrastive and text-generative kinds of losses. Comparatively, prior work is both not in a position to deal with image-text retrieval duties, or applies just some losses to just some components of the mannequin. To allow multimodal duties and totally reap the benefits of the decoder-only mannequin, we have to collectively practice each contrastive losses and text-generative captioning-like losses.

MaMMUT structure (left) is a straightforward assemble consisting of a single imaginative and prescient encoder and a single textual content decoder. In comparison with different well-liked vision-language fashions — e.g., PaLI (center) and ALBEF, CoCa (proper) — it trains collectively and effectively for a number of vision-language duties, with each contrastive and text-generative losses, totally sharing the weights between the duties.

Decoder two-pass studying

Decoder-only fashions for language studying present clear benefits in efficiency with smaller mannequin measurement (virtually half the parameters). The principle problem for making use of them to multimodal settings is to unify the contrastive studying (which makes use of unconditional sequence-level illustration) with captioning (which optimizes the chance of a token conditioned on the earlier tokens). We suggest a two-pass method to collectively be taught these two conflicting kinds of textual content representations throughout the decoder. In the course of the first move, we make the most of cross consideration and causal masking to be taught the caption era job — the textual content options can attend to the picture options and predict the tokens in sequence. On the second move, we disable the cross-attention and causal masking to be taught the contrastive job. The textual content options won’t see the picture options however can attend bidirectionally to all textual content tokens without delay to provide the ultimate text-based illustration. Finishing this two-pass method throughout the identical decoder permits for accommodating each kinds of duties that have been beforehand onerous to reconcile. Whereas easy, we present that this mannequin structure is ready to present a basis for a number of multimodal duties.

MaMMUT decoder-only two-pass studying permits each contrastive and generative studying paths by the identical mannequin.

One other benefit of our structure is that, since it’s skilled for these disjoint duties, it may be seamlessly utilized to a number of functions akin to image-text and text-image retrieval, VQA, and captioning.

Furthermore, MaMMUT simply adapts to video-language duties. Earlier approaches used a imaginative and prescient encoder to course of every body individually, which required making use of it a number of occasions. That is sluggish and restricts the variety of frames the mannequin can deal with, sometimes to solely 6–8. With MaMMUT, we use sparse video tubes for light-weight adaptation straight through the spatio-temporal data from the video. Moreover, adapting the mannequin to Open-Vocabulary Detection is completed by merely coaching to detect bounding-boxes through an object-detection head.

Adaptation of the MaMMUT structure to video duties (left) is easy and totally reuses the mannequin. That is completed by producing a video “tubes” function illustration, just like picture patches, which might be projected to decrease dimensional tokens and run by way of the imaginative and prescient encoder. In contrast to prior approaches (proper) that must run a number of particular person photographs by way of the imaginative and prescient encoder, we use it solely as soon as.


Our mannequin achieves glorious zero-shot outcomes on image-text and text-image retrieval with none adaptation, outperforming all earlier state-of-the-art fashions. The outcomes on VQA are aggressive with state-of-the-art outcomes, that are achieved by a lot bigger fashions. The PaLI mannequin (17B parameters) and the Flamingo mannequin (80B) have one of the best efficiency on the VQA2.0 dataset, however MaMMUT (2B) has the identical accuracy because the 15B PaLI.

MaMMUT outperforms the cutting-edge (SOTA) on Zero-Shot Picture-Textual content (I2T) and Textual content-Picture (T2I) retrieval on each MS-COCO (prime) and Flickr (backside) benchmarks.
Efficiency on the VQA2.0 dataset is aggressive however doesn’t outperform massive fashions akin to Flamingo-80B and PalI-17B. Efficiency is evaluated within the tougher open-ended textual content era setting.

MaMMUT additionally outperforms the state-of-the-art on VideoQA, as proven beneath on the MSRVTT-QA and MSVD-QA datasets. Observe that we outperform a lot larger fashions akin to Flamingo, which is particularly designed for picture+video pre-training and is pre-trained with each image-text and video-text knowledge.

MaMMUT outperforms the SOTA fashions on VideoQA duties (MSRVTT-QA dataset, prime, MSVD-QA dataset, backside), outperforming a lot bigger fashions, e.g., the 5B GIT2 or Flamingo, which makes use of 80B parameters and is pre-trained for each image-language and vision-language duties.

Our outcomes outperform the state-of-the-art on open-vocabulary detection fine-tuning as can be proven beneath.

Key components

We present that joint coaching of each contrastive and text-generative goals is just not a simple job, and in our ablations we discover that these duties are served higher by totally different design selections. We see that fewer cross-attention connections are higher for retrieval duties, however extra are most well-liked by VQA duties. But, whereas this exhibits that our mannequin’s design selections is likely to be suboptimal for particular person duties, our mannequin is simpler than extra advanced, or bigger, fashions.

Ablation research exhibiting that fewer cross-attention connections (1-2) are higher for retrieval duties (prime), whereas extra connections favor text-generative duties akin to VQA (backside).


We offered MaMMUT, a easy and compact vision-encoder language-decoder mannequin that collectively trains quite a few conflicting goals to reconcile contrastive-like and text-generative duties. Our mannequin additionally serves as a basis for a lot of extra vision-language duties, attaining state-of-the-art or aggressive efficiency on image-text and text-image retrieval, videoQA, video captioning, open-vocabulary detection and VQA. We hope it may be additional used for extra multimodal functions.


The work described is co-authored by: Weicheng Kuo, AJ Piergiovanni, Dahun Kim, Xiyang Luo, Ben Caine, Wei Li, Abhijit Ogale, Luowei Zhou, Andrew Dai, Zhifeng Chen, Claire Cui, and Anelia Angelova. We wish to thank Mojtaba Seyedhosseini, Vijay Vasudevan, Priya Goyal, Jiahui Yu, Zirui Wang, Yonghui Wu, Runze Li, Jie Mei, Radu Soricut, Qingqing Huang, Andy Ly, Nan Du, Yuxin Wu, Tom Duerig, Paul Natsev, Zoubin Ghahramani for his or her assist and help.

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