First generation
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Essence 1 and Expression 1, bitHuman's first-generation avatar models: what each one is, where it runs, and what its file contains. Both are maintained; new work starts on Essence 2 or Expression 2.
Both first-generation models are maintained, not deprecated. For new work, start on Essence 2 (a photoreal person) or Expression 2 (any character).
| Essence 1 | Expression 1 | |
|---|---|---|
| Renders | a pre-built identity from an .imx file | facial motion generated from a portrait at runtime |
| Where it runs | the bitHuman cloud; Python and the CLI on macOS and Linux; the browser (render=local) | the bitHuman cloud only |
model value | essence-1 | expression-1 |
Essence 1
Essence 1 (essence-1) reads a pre-built identity out of an .imx file, plays its base motion, and patches the mouth in real time to match 16 kHz mono audio, at 25 fps. It runs on a CPU, with no GPU or accelerator, and supports custom gestures. ?model=essence-1 serves it.
Where Essence 1 runs
In the bitHuman cloud, and on your own hardware through:
- Python:
pip install bithumanopens an Essence 1.imxwith no extra; see Python. - The CLI:
bithuman runon macOS (Apple silicon) and Linux x86_64 and arm64; see CLI.renderdoes not take Essence 1: use the Python SDK or the Talking video API for a file. - The browser:
?render=local.
Essence 1 is not in the Android SDK or the Swift package. On phones, use Essence 2 or Expression 2, or run Essence 1 from the cloud API, or from Python or the CLI on a desktop. The full matrix is on Compare models.
The Essence 1 file
One file, <CODE>.imx: the identity, and optionally baked-in idle and gesture clips. Download it with bithuman pull <CODE> --model essence-1, or:
curl -L -o "<CODE>.imx" -H "api-secret: $BITHUMAN_API_SECRET" \
"https://api.bithuman.ai/v1/agent/<CODE>/model/download?model=essence-1"Expression 1
Expression 1 (expression-1) animates a face from a portrait image at runtime: you give it audio, and it generates the facial motion to match, with no per-identity build step. ?model=expression-1 serves it, and it is what /v1/agent/generate creates when the request names no model.
It is a different engine from Expression 2, not an earlier version of it.
Where Expression 1 runs
In the bitHuman cloud only, on cloud GPUs. There is no CPU, Apple, Android or browser build. For an expressive model on a Mac, a phone or in a browser, use Expression 2.
Cloud output is 512×512. Expression 1 can also animate a photo with no agent: see Cloud avatar in your room.
The Expression 1 file
Usually there is nothing to download: Expression 1 renders from the agent’s portrait, so the download endpoint answers 400 MODEL_NOT_DOWNLOADABLE for most agents. A few older agents have a downloadable .imx, which the endpoint serves. The engine weights are not part of any download.
Pricing
Rates for both models are on Pricing and credits.