# Helios vs LongLive-2.0: inputs, controls and API cost

> Compare Helios and LongLive-2.0 APIs: inputs, outputs, streaming delivery and ready-second cost. Choose a Windflow model for your product.

Source: https://windflow.online/compare/helios-vs-longlive-2 · Updated 2026-10-11 · Windflow Labs

**Helios and LongLive-2.0 are both realtime video generation options in Windflow's public catalog.** Choose by the inputs and interaction you need, then evaluate quality and responsiveness with your actual application. This page compares the published serving profiles; it does not present a head-to-head performance experiment.

## Quick decision

- Evaluate [Helios](https://windflow.online/models/helios) for: Continuous generative video that never has to restart: ambient scenes, live backdrops, long takes.
- Evaluate [LongLive-2.0](https://windflow.online/models/longlive-2) for: Multi-shot narrative clips directed live, one text prompt per shot.

## Specifications side by side

| Published specification | Helios | LongLive-2.0 |
|---|---|---|
| Architecture | 14B Diffusion Transformer, autoregressive chunked diffusion | Autoregressive multi-shot DiT (Wan2.2-TI2V backbone) |
| Resolution | Negotiated per session | 1280 × 704 |
| Playout | Negotiated per session | Not published |
| Chunk | 33 native frames in the production profile | 29 frames |
| Control latency | First chunk after roughly one chunk of generation | Not published |
| Inputs | Text prompt (required before start) and an optional reference image for image-to-video | Text shot prompts only — no reference image in this release |
| Outputs | One continuous, steerable clip on the main_video track | A multi-shot clip on main_video; chunk_index resets per scene while session_chunk keeps counting |
| Delivery | WebSocket (H.264) · WebRTC | WebSocket (H.264) · WebRTC |
| Session protocol | sdk.realtime.v2 | sdk.realtime.v2 |
| Price | $0.0017 per ready second | $0.0021 per ready second |
| Scene budget | Not published | 48 chunks per scene; scene_cut opens a fresh budget |
| Implementation status | production | production |

Implementation status describes runtime maturity. Live GPU readiness is reported separately; Windflow is in private beta and brings capacity up on demand.

## Input and control fit

Both models accept text prompts in the published Windflow profile.
Helios accepts reference or seed images; LongLive-2.0 does not in its published profile.
Both models do not accept uploaded source clips in the published Windflow profile.
Both models do not accept live webcam input in the published Windflow profile.
Both models do not accept movement and look controls in the published Windflow profile.

A shared session API does not make commands interchangeable. Use each model's supported inputs and control timing. In particular, prompt changes may land at a chunk or generation-window boundary; movement input can represent persistent state until replaced.

## What Helios is designed for

Helios is a 14-billion-parameter, open-source video diffusion model from the PKU-YuanGroup research lab, built to generate long video continuously rather than as a fixed-length clip. On Windflow it runs as a realtime session: you set the opening prompt, start the stream, and keep steering the same continuous clip while frames arrive live.

- Continuous generative video that never has to restart: ambient scenes, live backdrops, long takes.
- Prompt-steered storytelling where each prompt change continues the scene instead of cutting away.
- Image-to-video runs that start from a reference image and keep going.
- Prototyping interactive video products before committing to a heavier world model.

## What LongLive-2.0 is designed for

LongLive-2.0 is an autoregressive, multi-shot video diffusion model from NVIDIA Research (NVlabs), built on a Wan2.2-TI2V backbone and designed to keep a long video coherent as the prompt changes. On Windflow you direct it with text shot prompts: switch the shot softly while it runs, or cut to a new scene.

- Multi-shot narrative clips directed live, one text prompt per shot.
- Interactive long-form video where a viewer or an agent decides what happens next.
- Storyboard-to-motion experiments that need scene-to-scene continuity.
- Streams that run scene after scene without a fixed end point.

## Compare a realistic session budget

- Helios: $0.0017 per ready second, or $1.02 for ten ready minutes.
- LongLive-2.0: $0.0021 per ready second, or $1.26 for ten ready minutes.

Queueing and worker startup are free. A ready owner session can remain billable while delivery is paused or unwatched; release it when done. Independent sessions carry independent meters. Use the [cost calculator](https://windflow.online/tools/ai-video-cost-calculator) to estimate your duration and daily sessions.

## Evaluate before choosing

Use one repeatable input sequence, the same client and network, and equivalent output expectations. Record first visible frame, control-to-visible delay, frame gaps, scene continuity and rejected controls. Run several starts and a sustained session. If serving profiles differ, label the differences instead of treating displayed FPS as directly comparable native generation speed.

See [the latency measurement guide](https://windflow.online/guides/measure-realtime-video-latency) and [the model selector](https://windflow.online/tools/ai-video-model-selector) for a reproducible decision process.

## Sources

- [PKU-YuanGroup/Helios on GitHub](https://github.com/PKU-YuanGroup/Helios) — Apache-2.0
- [NVlabs/LongLive on GitHub](https://github.com/NVlabs/LongLive) — Apache-2.0

## FAQ

### Is Helios better than LongLive-2.0?

The answer depends on the inputs, control behavior, quality and output your product requires. The published specifications identify capability differences; an application-level evaluation establishes performance for your scenario.

### Can I switch between these models through the same API?

Windflow keeps the session lifecycle common. Your application must adapt to each model's supported inputs, commands, output tracks and generation timing.

### Do the published prices guarantee available GPU capacity?

No. Rates and implementation status are catalog facts. Live readiness is a separate operational signal, and private-beta access is required to run sessions.