Captions is the leading video AI company, building the future of video creation. Over 10 million creators and businesses have used Captions to create videos for social media, marketing, sales, and more. We're on a mission to serve the next billion.

We are a rapidly growing team of ambitious, experienced, and devoted engineers, researchers, designers, marketers, and operators based in NYC. You'll join an early team and have an outsized impact on the product and the company's culture.

We’re very fortunate to have some the best investors and entrepreneurs backing us, including Index Ventures (Series C lead), Kleiner Perkins (Series B lead), Sequoia Capital (Series A and Seed co-lead), Andreessen Horowitz (Series A and Seed co-lead), Uncommon Projects, Kevin Systrom, Mike Krieger, Lenny Rachitsky, Antoine Martin, Julie Zhuo, Ben Rubin, Jaren Glover, SVAngel, 20VC, Ludlow Ventures, Chapter One, and more.

Check out our latest financing milestone and some other coverage:

The Information: 50 Most Promising Startups

Fast Company: Next Big Things in Tech

The New York Times: When A.I. Bridged a Language Gap, They Fell in Love

Business Insider: 34 most promising AI startups

Time: The Best Inventions of 2024

** Please note that all of our roles will require you to be in-person at our NYC HQ (located in Union Square) **

Overview

Captions is seeking an exceptional Research Engineer to advance the state-of-the-art in large-scale multimodal video diffusion models. You'll conduct novel research on generative modeling architectures, develop new training techniques, and scale models to billions of parameters. As a key member of our ML Research team, you'll work at the cutting edge of multimodal generation while building systems that enable natural, controllable video creation. We're already training large-scale models with demonstrated product impact, and we're excited to continue expanding the scope and capabilities of our research.

We're especially excited about pushing the boundaries of audio-video generation, with a focus on realistic and charismatic human behavior that enables natural storytelling and creative iteration. Our models power creative tools used by millions of creators, and we're tackling fundamental challenges in how to generate compelling human motion, expression, and speech. 

Key Responsibilities

Research & Architecture Development:

• Design and implement novel architectures for large-scale video and multimodal diffusion models

• Develop new approaches to multimodal fusion, temporal modeling, and video control

• Research temporal video editing techniques and controllable generation

• Research and validate scaling laws for video generation models

• Create new loss functions and training objectives for improved generation quality

• Drive rapid experimentation with model architectures and training strategies

• Validate research directly through product deployment and user feedback

Model Training & Optimization:

• Train and optimize models at massive scale (10s-100s of billions of parameters)

• Develop sophisticated distributed training approaches using FSDP, DeepSpeed, Megatron-LM

• Design and implement model surgery techniques (pruning, distillation, quantization)

• Create new approaches to memory optimization and training efficiency

• Research techniques for improving training stability at scale

• Conduct systematic empirical studies of architecture and optimization choices

Technical Innovation:

• Advance state-of-the-art in video model architecture design and optimization 

• Develop new approaches to temporal modeling for video generation

• Create novel solutions for multimodal learning and cross-modal alignment

• Research and implement new optimization techniques for generative modeling and sampling

• Design and validate new evaluation metrics for generation quality

• Systematically analyze and improve model behavior across different regimes

Preferred Qualifications

Research Experience:

• Master's or PhD in Computer Science, Machine Learning, or related field

• Track record of research contributions at top ML conferences (NeurIPS, ICML, ICLR)

• Demonstrated experience implementing and improving upon state-of-the-art architectures

• Deep expertise in generative modeling approaches (diffusion, autoregressive, VAEs, etc.)

• Strong background in optimization techniques and loss function design

• Experience with empirical scaling studies and systematic architecture research

Technical Expertise:

• Strong proficiency in modern deep learning tooling (PyTorch, CUDA, Triton, FSDP, etc.)

• Experience training diffusion models with 10B+ parameters

• Experience with very large language models (200B+ parameters) is a plus

• Deep understanding of attention, transformers, and modern multimodal architectures

• Expertise in distributed training systems and model parallelism

• Proven ability to implement and improve complex model architectures

• Track record of systematic empirical research and rigorous evaluation

Engineering Capabilities:

• Ability to write clean, modular research code that scales

• Strong software engineering practices including testing and code review

• Experience with rapid prototyping and experimental design

• Strong analytical skills for debugging model behavior and training dynamics

• Facility with profiling and optimization tools

• Track record of bringing research ideas to production

• Experience maintaining high code quality in a research environment

Team Culture

You'll work directly alongside our research and engineering teams in our NYC office. We've intentionally built a culture where technical innovation and research excellence are highly valued - your success will be measured by your contributions to improving our models and advancing the field, not by your ability to navigate politics. We're a team that loves diving deep into complex technical problems and emerging with practical breakthroughs.

• Our team values:

  • Open technical discussions and collaboration

  • Rapid iteration and practical solutions

  • Deep technical expertise and continuous learning

  • Direct impact on research and product outcomes

• What sets us apart:

  • Opportunity to advance the state-of-the-art in video generation

  • Direct impact on products used by millions of creators

  • Access to massive compute resources and diverse, large-scale datasets

  • Environment that values both research excellence and practical impact

  • Ability to validate research through direct product feedback

Benefits:

• Comprehensive medical, dental, and vision plans

• 401K with employer match

• Commuter Benefits

• Catered lunch multiple days per week

• Dinner stipend every night if you're working late and want a bite!

• Doordash DashPass subscription

• Health & Wellness Perks (Talkspace, Kindbody, One Medical subscription, HealthAdvocate, Teladoc)

• Multiple team offsites per year with team events every month

• Generous PTO policy and flexible WFH days

Captions provides equal employment opportunities to all employees and applicants for employment and prohibits discrimination and harassment of any type without regard to race, color, religion, age, sex, national origin, disability status, genetics, protected veteran status, sexual orientation, gender identity or expression, or any other characteristic protected by federal, state or local laws.

Please note benefits apply to full time employees only.