Murf BVC for LiveKit Agents

Background voice cancellation for voice agents. Murf BVC keeps the person talking to your agent and removes everyone and everything else (TV, other people in the room, street and office noise) before your agent's VAD, turn detection and speech-to-text see the audio. Fewer false interruptions, fewer transcripts of someone else's words.

It runs on CPU inside your agent process, like LiveKit's own noise-cancellation plugin. No GPU and no extra services; audio never leaves your process.

Requirements

• Python 3.10+ and livekit-agents 1.2+
• Linux (glibc 2.28+: Ubuntu 20.04+, Debian 10+, RHEL/Rocky/Alma 8+, Amazon Linux 2023) on x86_64 or aarch64, or macOS 11+ (Apple Silicon) / 10.15+ (Intel)
• x86_64 CPUs need AVX2 and FMA (Intel Haswell / 2013 or newer, any AMD Zen); on ARM, AWS Graviton2 or newer, or any Apple Silicon Mac
• A Murf API key with BVC enabled, or an offline license key for on-premise and air-gapped deployments (contact Murf)

Install

pip install livekit-plugins-murf-bvc

Quick start

Pass murf_bvc.BVC(...) with your key as the noise cancellation for the room's audio input:

from livekit.agents import Agent, AgentSession, JobContext, WorkerOptions, cli, room_io
from livekit.plugins import murf_bvc


async def entrypoint(ctx: JobContext):
    session = AgentSession(...)  # your STT, LLM, TTS, VAD, turn detection
    bvc = murf_bvc.BVC(api_key=load_murf_api_key())  # from your secrets manager

    await session.start(
        room=ctx.room,
        agent=Agent(instructions="You are a helpful assistant."),
        room_options=room_io.RoomOptions(
            audio_input=room_io.AudioInputOptions(noise_cancellation=bvc),
        ),
    )


if __name__ == "__main__":
    cli.run_app(WorkerOptions(entrypoint_fnc=entrypoint))

That's all most agents need. The defaults are what we recommend for production. On-premise or air-gapped, pass license_key="mbvc1...." (an offline license from Murf) instead of api_key.

Keys

Pass the key in code, as above, rather than through the environment. The key then applies only to that BVC value and the streams it creates, never enters LiveKit's options, and is not inherited by subprocesses or visible in the process environment, where crash reporters and debugging tools often collect it. A BVC() created without a key is not licensed by another one's key.

Without a key argument, BVC() falls back to the environment: MURF_BVC_LICENSE, then MURF_API_KEY.

Any code running in your agent process (other plugins included) can read memory it shares with the agent, so no way of passing a key hides it from them. Treat the BVC key like the agent's other API keys.

Options: when to change them

murf_bvc.BVC(api_key=None, license_key=None, restore=True, normalize=True, native=True)

Rooms with several participants

Nothing to change: one BVC() value serves every participant, each with its own independent state.

If you use native=False (or BVCProcessor directly), each processor handles one track, so pass a selector instead:

noise_cancellation=lambda params: murf_bvc.BVC(native=False)

What to expect

• Latency: 10 ms at 16 kHz, about 13.6 ms at 24 or 48 kHz (resampling included).
• CPU: about 3% of one core per active participant on an AWS AMD EPYC instance, plus a speaker check every 0.5 s of speech while caller restore is on. Processing is single-threaded per stream, so it scales with the number of concurrent calls.
• Audio: any sample rate LiveKit delivers (8–96 kHz); stereo input is mixed to mono.

License behaviour

Without a valid license BVC does not stop your agent: it logs an error and passes audio through unchanged, delayed by the same few milliseconds, so calls keep working and a license expiring mid-call never knocks audio out of sync.

With an API key, the first BVC(api_key=...) in a process waits up to 5 s for its first lease (later ones return at once). If Murf cannot be reached, processing continues on the current lease for at least 45 minutes; after it expires audio passes through until a renewal succeeds, then processing resumes on its own.

Check a key at startup:

assert murf_bvc.licensed(api_key=key)   # or license_key=...; the reason is logged if not

Troubleshooting