bithuman 1.10.4

Real-time avatar engine — 100+ FPS on CPU. Generate lip-synced video, stream live avatars to browsers. 1-2 CPU cores, <200ms latency. ARM, x86, macOS.

bitHuman Avatar Runtime

Real-time avatar engine for visual AI agents, digital humans, and creative characters.

bitHuman powers visual AI agents and conversational AI with photorealistic avatars and real-time lip-sync. Build voice agents with faces, video chatbots, AI assistants, and interactive digital humans — all running on edge devices with typically 1-2 CPU cores and <200ms latency. Raw generation speed reaches up to 100+ FPS on CPU alone in typical configurations, enabling real-time streaming applications.

The SDK supports two model families through the same AsyncBithuman API:

Model type	Runtime	Where it runs
Essence	In-process (native)	Linux / macOS / Windows, x86_64 + ARM64. Default — what every existing caller uses.
Expression	Out-of-process Swift runtime	macOS + Apple Silicon (M3+) only. Ships with the macOS arm64 wheel; dispatches automatically when the model file is an Expression model.

A single call — AsyncBithuman.create(model_path=…) — works for both. If the model can't run on the current host, you get a typed ExpressionModelNotSupported instead of a cryptic crash.

See docs/architecture.md for the full picture across all repos; docs/best-practices.md for production patterns.

Installation

pip install bithuman --upgrade

Pre-built wheels for all major platforms — no compilation required:

	Linux	macOS	Windows
x86_64	yes	yes	yes
ARM64	yes	yes (Apple Silicon)	—
Python	3.9 — 3.14	3.9 — 3.14	3.9 — 3.14

For LiveKit agent integration:

pip install bithuman[agent]

Quick Start

Generate a lip-synced video

bithuman generate avatar.imx --audio speech.wav --key YOUR_API_KEY

Stream a live avatar to your browser

# Terminal 1: Start the streaming server
bithuman stream avatar.imx --key YOUR_API_KEY

# Terminal 2: Send audio to trigger lip-sync
bithuman speak speech.wav

Open http://localhost:3001 to see the avatar streaming live.

Python API (async)

import asyncio
from bithuman import AsyncBithuman
from bithuman.audio import load_audio, float32_to_int16

async def main():
    # Same entry point for every model type. On macOS + Apple Silicon
    # (M3+) this auto-detects Expression `.imx` bundles and dispatches
    # to the on-device Swift runtime; everywhere else it runs the
    # in-process Essence engine.
    runtime = await AsyncBithuman.create(
        model_path="avatar.imx",
        api_secret="YOUR_API_KEY",
    )
    await runtime.start()  # no-op for Expression, spins up the producer for Essence

    # Load and stream audio
    audio, sr = load_audio("speech.wav")
    audio_int16 = float32_to_int16(audio)

    async def stream_audio():
        chunk_size = sr // 25  # match video FPS
        for i in range(0, len(audio_int16), chunk_size):
            await runtime.push_audio(
                audio_int16[i:i + chunk_size].tobytes(), sr
            )
        await runtime.flush()

    asyncio.create_task(stream_audio())

    # Receive lip-synced video frames
    async for frame in runtime.run():
        if frame.has_image:
            image = frame.bgr_image       # numpy (H, W, 3), uint8
            audio = frame.audio_chunk     # synchronized audio
        if frame.end_of_speech:
            break

    await runtime.stop()  # alias for shutdown() — works for both runtimes

asyncio.run(main())

Python API (sync)

from bithuman import Bithuman
from bithuman.audio import load_audio, float32_to_int16

runtime = Bithuman.create(model_path="avatar.imx", api_secret="YOUR_API_KEY")

audio, sr = load_audio("speech.wav")
audio_int16 = float32_to_int16(audio)

chunk_size = sr // 100
for i in range(0, len(audio_int16), chunk_size):
    runtime.push_audio(audio_int16[i:i+chunk_size].tobytes(), sr)
runtime.flush()

for frame in runtime.run():
    if frame.has_image:
        image = frame.bgr_image
    if frame.end_of_speech:
        break

How It Works

1. Load model — .imx file contains the avatar's appearance, animations, and lip-sync data
2. Push audio — Stream audio bytes in real-time via push_audio(), call flush() when done
3. Get frames — Iterate runtime.run() to receive lip-synced video frames with synchronized audio

The runtime handles the full motion graph internally: idle animations, talking with lip-sync, head movements, blinking, and smooth transitions between states.

Performance

Metric	Value
Raw FPS	100+ on CPU (Intel i5-12400, Apple M2)
CPU cores	1-2 cores at 25 FPS
End-to-end latency	<200ms
Memory (IMX v2)	~200 MB per session
Model load time	<10ms (IMX v2)
Audio formats	WAV, MP3, FLAC, OGG, M4A

Features

• Real-time lip-sync — Audio-driven mouth animation at 25 FPS with synchronized audio output
• Cross-platform — Linux, macOS, Windows; x86_64 and ARM64; Python 3.9-3.14
• Edge-ready — 1-2 CPU cores, no GPU required for inference
• Sync + Async — Bithuman for threads, AsyncBithuman for async/await
• Streaming-first — Push audio chunks in real-time, receive frames as they're generated
• Actions & emotions — Trigger avatar gestures (wave, nod) and emotion states (joy, surprise)
• Interrupt support — Cancel mid-speech for natural conversation flow
• LiveKit integration — Built-in support for LiveKit Agents (WebRTC streaming)
• CLI tools — Generate videos, stream live, convert models, validate setups
• IMX v2 format — Optimized binary container with O(1) random access and WebP patches
• Zero scipy dependency — Pure numpy audio pipeline, minimal install footprint
• Expression models on macOS (Apple Silicon M3+) — AsyncBithuman.create() auto-detects .imx files whose manifest stamps model_type: "expression" and dispatches to the native Swift runtime out-of-process. Frames and audio stream back over an async pipe at 1500+ FPS (mock-daemon benchmark, amortized), and the public API stays unchanged. See bithuman-expression-swift.

Expression model support (macOS arm64)

The bithuman wheel for macOS Apple Silicon (M3+) ships a pre-built bithuman-expression-daemon binary from the bithuman-expression-swift SDK. When you load an .imx packed with bithuman pack, AsyncBithuman.create() detects the Expression manifest and transparently spawns the Swift daemon; subsequent push_audio / run / flush calls behave exactly like they do for Essence models.

from bithuman import AsyncBithuman

# Realtime streaming with the bundle's default identity:
runtime = await AsyncBithuman.create(
    model_path="expression.imx",
    api_secret=os.environ["BITHUMAN_API_SECRET"],
)

# Pick a face per agent — one shared model bundle, any portrait:
runtime = await AsyncBithuman.create(
    model_path="expression.imx",        # ~3.5 GB, shared across every agent
    api_secret=os.environ["BITHUMAN_API_SECRET"],
    identity="alice.jpg",               # ~few KB per face — encoded on load
)

# Offline video generation: higher quality, ~2× slower:
runtime = await AsyncBithuman.create(
    model_path="expression.imx",
    api_secret=os.environ["BITHUMAN_API_SECRET"],
    quality="high",
)

# Standard streaming loop:
await runtime.push_audio(pcm_bytes, sample_rate=24_000)
async for frame in runtime.run():
    display(frame.bgr_image)            # BGR uint8; shape matches the
                                        # face renderer the model was
                                        # packed with (384/448/512)

# Switch the avatar's face mid-session — no reload, no audio interruption
# beyond the in-flight chunk:
await runtime.set_identity("bob.jpg")

Identity (Expression models only)

The model bundle and the avatar face are now separate. Same expression.imx (~3.5 GB animator + speech encoder + face encoder + face renderer) drives any portrait you point it at.

identity=	Cost on load	Cost on swap	Notes
None (default)	0	n/a	Uses the face baked into the .imx at pack time
"face.jpg" / .png	~300 ms (M3+)	~300 ms	Encodes via the face encoder shipping in the bundle
"face.npy"	instant	instant	Pre-encoded latent — produced by encode-ref-latent or cached from a previous swap

Switch any time:

await runtime.set_identity("alice.jpg")    # encode + swap
await runtime.set_identity("alice_cached.npy")    # instant
await runtime.set_identity(None)           # restore bundle default

On Linux, Windows, and Intel macOS, the daemon binary isn't bundled and Expression models raise ExpressionModelNotSupported with install guidance. The in-process Essence runtime is unaffected on every platform.

Quality preset (Expression models only)

quality	When to use	Realtime factor (M5, 384×384)	Realtime factor (M5, 512×512)
"medium"	Live streaming (default)	1.84×	1.14×
"high"	Offline video generation	1.05×	0.67× ⚠

"high" is sub-realtime at 512×512 on an M5 — use it only for pre-recorded video export, not live streams. Ignored for Essence models.

Packing at different resolutions

bithuman pack bundles five weight artifacts into a single .imx avatar model file. The 384×384 face renderer is the realtime default — it leaves ~1 s of headroom per second of audio on an M5. Swap in the 448 or 512 renderer + a matching reference-face to produce higher-resolution output; the companion bithuman-expression-swift repo ships an encode-ref-latent tool that generates a reference-face file at any resolution from a portrait image.

# 384×384 — recommended for streaming
bithuman pack \
    --animator        path/to/animator.safetensors \
    --speech-encoder  path/to/speech_encoder.safetensors \
    --face-encoder    path/to/face_encoder.safetensors \
    --face-renderer   path/to/face_renderer_384.mlpackage \
    --reference-face  path/to/reference_face_384.npy \
    -o expression.imx

# 512×512 — offline video quality
bithuman pack \
    --animator        path/to/animator.safetensors \
    --speech-encoder  path/to/speech_encoder.safetensors \
    --face-encoder    path/to/face_encoder.safetensors \
    --face-renderer   path/to/face_renderer_512.mlpackage \
    --reference-face  path/to/reference_face_512.npy \
    -o expression_512.imx

Old ML-term flag names (--dit, --wav2vec, --vae-encoder, --ane-decoder, --ref-latent, --pos-conv) continue to work as aliases so existing build scripts don't break.

API Reference

AsyncBithuman / Bithuman

The main runtime for avatar animation.

# Create and initialize
runtime = await AsyncBithuman.create(
    model_path="avatar.imx",     # Path to .imx model
    api_secret="API_KEY",        # API secret (recommended)
    # token="JWT_TOKEN",         # Or JWT token directly
)
await runtime.start()

# Push audio (int16 PCM, any sample rate — auto-resampled to 16kHz)
await runtime.push_audio(audio_bytes, sample_rate)
await runtime.flush()            # Signal end of speech
runtime.interrupt()              # Cancel current playback

# Receive frames
async for frame in runtime.run():
    frame.bgr_image              # np.ndarray (H, W, 3) uint8 BGR
    frame.rgb_image              # np.ndarray (H, W, 3) uint8 RGB
    frame.audio_chunk            # AudioChunk — synchronized audio
    frame.end_of_speech          # True when all audio processed
    frame.has_image              # True if image available
    frame.frame_index            # Frame number
    frame.source_message_id      # Correlates to input

# Controls
await runtime.push(VideoControl(action="wave"))          # Trigger action
await runtime.push(VideoControl(target_video="idle"))    # Switch state
runtime.set_muted(True)                                  # Mute processing

# Info
runtime.get_frame_size()          # (width, height)
runtime.get_first_frame()         # First idle frame as np.ndarray
runtime.get_expiration_time()     # Token expiry (unix timestamp)
runtime.is_token_validated()      # Auth status

await runtime.stop()

Data Classes

from bithuman import AudioChunk, VideoControl, VideoFrame, Emotion, EmotionPrediction

# AudioChunk — container for audio data
chunk = AudioChunk(data=np.array([...], dtype=np.int16), sample_rate=16000)
chunk.duration    # float — length in seconds
chunk.bytes       # bytes — raw PCM bytes

# VideoControl — input to the runtime
ctrl = VideoControl(
    audio=chunk,                    # Audio to lip-sync
    action="wave",                  # Trigger action (wave, nod, etc.)
    target_video="talking",         # Switch video state
    end_of_speech=True,             # Mark end of speech
    force_action=False,             # Override action deduplication
    emotion_preds=[                 # Set emotion state
        EmotionPrediction(emotion=Emotion.JOY, score=0.9),
    ],
)

# VideoFrame — output from runtime.run()
frame.bgr_image           # np.ndarray (H, W, 3) uint8 — BGR
frame.rgb_image           # np.ndarray (H, W, 3) uint8 — RGB
frame.audio_chunk         # AudioChunk — synchronized audio
frame.end_of_speech       # bool — True when done
frame.has_image           # bool — True if image available
frame.frame_index         # int — frame number
frame.source_message_id   # Hashable — correlates to VideoControl

# Emotion enum
Emotion.ANGER | Emotion.DISGUST | Emotion.FEAR | Emotion.JOY
Emotion.NEUTRAL | Emotion.SADNESS | Emotion.SURPRISE

Audio Utilities

from bithuman.audio import (
    load_audio,               # Load WAV/MP3/FLAC/OGG/M4A -> (float32, sr)
    float32_to_int16,         # float32 -> int16
    int16_to_float32,         # int16 -> float32
    resample,                 # Resample to target rate
    write_video_with_audio,   # Save MP4 with audio track
    AudioStreamBatcher,       # Real-time audio buffer
)

audio, sr = load_audio("speech.mp3")             # Any format
audio_int16 = float32_to_int16(audio)            # Ready for push_audio
audio_16k = resample(audio, sr, 16000)           # Resample
write_video_with_audio("out.mp4", frames, audio, sr, fps=25)

Exceptions

All exceptions inherit from BithumanError:

Exception	When
TokenExpiredError	JWT has expired
TokenValidationError	Invalid signature or claims
TokenRequestError	Auth server unreachable
AccountStatusError	Billing or access issue (HTTP 402/403)
ModelNotFoundError	Model file doesn't exist
ModelLoadError	Corrupt or incompatible model
ModelSecurityError	Security restriction triggered
RuntimeNotReadyError	Operation called before initialization

LiveKit Agent Integration

Build conversational AI agents with avatar faces using LiveKit Agents:

from bithuman import AsyncBithuman
from bithuman.utils.agent import LocalAvatarRunner, LocalVideoPlayer, LocalAudioIO

# Initialize bitHuman runtime
runtime = await AsyncBithuman.create(
    model_path="avatar.imx",
    api_secret="YOUR_API_KEY",
)

# Connect to LiveKit agent session
avatar = LocalAvatarRunner(
    bithuman_runtime=runtime,
    audio_input=session.audio,
    audio_output=LocalAudioIO(session, agent_output),
    video_output=LocalVideoPlayer(window_size=(1280, 720)),
)
await avatar.start()

See the examples in the bithuman-examples repo for a complete working LiveKit Agent example with OpenAI Realtime voice.

Optimize Your Models

Convert existing .imx models to IMX v2 for dramatically better performance:

bithuman convert avatar.imx

Metric	Legacy (TAR)	IMX v2	Improvement
Model size	100 MB	50-70 MB	30-50% smaller
Load time	~10s	<10ms	up to 1000x faster
Runtime speed	~30 FPS	100+ FPS	3-10x faster
Peak memory	~10 GB	~200 MB	up to 98% less

Measured against the legacy TAR format with internal benchmarks; actual gains vary by hardware, model, and workload.

Conversion is automatic on first load, but pre-converting saves startup time.

CLI Reference

Command	Description
bithuman generate <model> --audio <file>	Generate lip-synced MP4 from model + audio
bithuman stream <model>	Start live streaming server at localhost:3001
bithuman speak <audio>	Send audio to running stream server
bithuman action <name>	Trigger avatar action (wave, nod, etc.)
bithuman info <model>	Show model metadata
bithuman list-videos <model>	List all videos in a model
bithuman convert <model>	Convert legacy to optimized IMX v2
bithuman validate <path>	Validate model files load correctly

Configuration

Environment Variables

Variable	Description
BITHUMAN_API_SECRET	API secret for authentication
BITHUMAN_RUNTIME_TOKEN	JWT token (alternative to API secret)
BITHUMAN_VERBOSE	Enable debug logging
CONVERT_THREADS	Number of threads for model conversion (0 or unset = auto-detect)

Runtime Settings

Setting	Default	Description
FPS	25	Target frames per second
OUTPUT_WIDTH	1280	Output frame width (0 = native resolution)
PRELOAD_TO_MEMORY	False	Cache model in RAM for faster decode
PROCESS_IDLE_VIDEO	True	Run inference during silence (natural idle)

Use Cases

• Visual AI Agents — Give your voice agents a face with real-time lip-sync
• Conversational AI — Build video chatbots and AI assistants with human-like presence
• Live Streaming — Stream avatars to browsers via WebSocket, LiveKit, or WebRTC
• Video Generation — Generate lip-synced content from audio at 100+ FPS
• Edge AI — Run locally on Raspberry Pi, Mac Mini, Chromebook, or any edge device
• Digital Twins — Photorealistic replicas for customer service, education, or entertainment

Examples

Example	Description
example.py	Async runtime with live video + audio playback
example_sync.py	Synchronous runtime with threading
livekit_agent/	LiveKit Agent with OpenAI Realtime voice
livekit_webrtc/	WebRTC streaming server

See the bithuman-examples repo for the complete set of runnable examples.

Troubleshooting

macOS: Duplicate FFmpeg library warnings

objc: Class AVFFrameReceiver is implemented in both .../cv2/.dylibs/libavdevice...
and .../av/.dylibs/libavdevice...

This happens when opencv-python (full) is installed alongside av (PyAV) — both bundle FFmpeg dylibs. Fix by switching to the headless variant:

pip install opencv-python-headless

This replaces opencv-python and removes the duplicate dylibs. The bithuman package already depends on opencv-python-headless, so this only occurs when another package has pulled in the full opencv-python.

Model conversion fails with TypeError

If you see TypeError: an integer is required during conversion, upgrade to the latest version:

pip install bithuman --upgrade

This was fixed in v1.6.2. The issue affected models in legacy TAR format during auto-conversion.

Getting a bitHuman Model

To create your own avatar model (.imx file):

1. Visit bithuman.ai
2. Register and subscribe
3. Upload a photo or video to create your avatar
4. Download your .imx model file

Links

• Documentation
• GitHub (this repo)
• PyPI
• Changelog
• Swift SDK (Expression runtime)
• Halo (reference macOS app)
• Examples
• bithuman.ai

Related documentation

• docs/architecture.md — two-runtime, three-repo architecture across the whole stack
• docs/essence-architecture.md — deep dive on the Essence in-process pipeline
• docs/best-practices.md — production patterns (pick the right runtime, handle billing, pair audio with flush, etc.)

License

Commercial license required. See bithuman.ai for pricing.