multimodal

Cross-attention is how a model attends from one sequence into another, the mechanism behind encoder-decoder models and multimodal conditioning. What shows depth is knowing exactly where the queries versus keys/values come from.

VLMs such as GPT-4V and LLaVA attach a vision encoder to a language model through a projector. The signal is the image-tokens-as-prefix design, the alignment training, and the resolution and hallucination failure modes.

Speech LLMs either transcribe to text or model audio straight away as discrete tokens. The signal is the semantic-vs-acoustic token split and why end-to-end audio models outperform ASR-plus-LLM pipelines on latency and prosody.

Four fusion families, and the choice between them is decided by one question most candidates never ask. Naming CLIP and LLaVA is table stakes; the score comes from knowing which one cannot reason and which one eats your context window.

Video breaks a VLM on arithmetic before it breaks it on vision: one frame per second of a ten-minute clip is hundreds of thousands of image tokens. Frame selection is not preprocessing, it is the architecture, and the strongest systems index the audio first.

A VLM is three parts and the interview is entirely about which ones you train. The staged recipe, why the vision encoder almost always stays frozen, and the silent failure where your model learns to answer from the text prior and never looks at the image.

The agent loop assumes an observation is a short string, and images break that assumption in both directions. The signal is a context policy that keeps pixels out of the transcript and a verification step for the files the agent produces.

Multimodal is now table stakes, and this tests whether you understand how images and text reach a shared model. The signal is CLIP's contrastive alignment and how modern VLMs feed image features into an LLM's token space.

A model that never looks at the image can score respectably on VQA, which tells you most of what you need to know about the benchmark. Here is what the scores hide, and the one-line ablation that exposes it.

An eval suite that never varies the image will happily pass a model that has stopped looking at it. Start with the modality ablation, then pick metrics by what the system actually produces. Here is the full stack.

Multimodal search checks whether you grasp shared embedding spaces and the retrieve-then-rank pattern under a real catalog's scale and freshness. What interviewers reward: CLIP-style joint embeddings, hybrid retrieval, and honest relevance evaluation. This lays out the design.

Image search is embedding retrieval at billion-image scale. A strong answer shows when a vision-only encoder is enough and when you need a CLIP-style shared space, plus how the ANN index actually serves the query. Here is the design.

Video search is image search plus a time axis, and the time axis is the whole problem. A strong answer embeds frames, pools them into scene vectors, indexes with ANN at billion scale, and explains how a multimodal query (clip, text, or both) locates the right moment, not just the right video.

You cannot review a live stream after publishing, because it already reached the audience. The broadcast delay buffer is the design, and everything else (frame sampling, the audio channel, the cascade) is built to fit inside it. Here is how it fits together.

An image is not one input, it is a large prompt. Once you internalize that image tokens dominate prefill, the cost levers stop being model choices and start being resolution, tiling, and cache placement.

Your guardrail reads text. The attack is not in the text. That single sentence is the whole vulnerability, and the red team you build from it looks nothing like the one you already have.