ojin-client 0.8.1

Ojin platform services

Ojin Python SDK

Real-time talking faces for human agents that resonate. Stream audio in, get a lip-synced avatar back — on a real-time clock, straight from Python.

Ojin is the real-time GenAI platform. Our focus is human agents — lifelike, conversational presences with a real voice, face, and soul, available 24/7. This SDK is the open, framework-agnostic way to drive the models that bring them to life: feed it your TTS audio and it returns a synchronized speech-to-video stream (audio + a talking-avatar video), handling buffering, the playback clock, and barge-in for you.

It's the same client that powers Ojin's own Pipecat integration — and it's yours to build agents, demos, and tools on top of.

• 🗣️ One image → a persona. Drive any avatar configuration from your Ojin account by its config_id.
• ⚡ Real-time by design. TCP_NODELAY, off-loop JPEG decode, and an audio-as-clock loop emit a steady 25 fps A/V stream.
• 🔌 Framework-agnostic. No Pipecat, no LiveKit, no web framework required. Drop it into anything async.
• 🎚️ Interruptible. First-class barge-in with audio fade and server-side cancel re-sync.
• 🧩 Swappable internals. Bring your own transport, resampler, JPEG decoder, output sink, or tracer behind small protocols.

---

Two clients, one package

	OjinSTVClient (high-level)	OjinClient (low-level)
Import	from ojin.stv import OjinSTVClient	from ojin.ojin_client import OjinClient
You give it	TTS audio at any sample rate	16 kHz mono int16 PCM
It gives you	Synced STVAudioFrame + STVVideoFrame on a 25 fps clock	Raw OjinInteractionResponseMessage (JPEG + PCM)
Handles for you	Buffering, playback clock, resampling, interruption re-sync, decode	Just the WebSocket + wire protocol
Extra deps	ojin-client[stv] (numpy / opencv-python-headless / soxr)	none
Use it when	You want a working talking avatar fast	You need full control of the loop

Most applications want OjinSTVClient. Reach for OjinClient only when you're writing your own playback/sync layer.

---

Requirements

• Python 3.10+
• An Ojin API key and a persona config_id — create both in your Ojin account (new accounts start with $10 in free credits).

Installation

With uv (recommended):

uv add "ojin-client[stv]"          # high-level OjinSTVClient (in a uv project)
uv pip install "ojin-client[stv]"  # ...or into the active environment

Or with pip:

pip install "ojin-client[stv]"     # high-level OjinSTVClient
pip install ojin-client            # low-level OjinClient only

The [stv] extra pulls in numpy, opencv-python-headless, and soxr for the sync math, default JPEG decoder, and resampler. If you inject your own decoder/resampler you can stay on the base install.

Developing against a local checkout of this repo? Install it editable: uv pip install -e ".[stv]" (or pip install -e ".[stv]").

Authentication

The client authenticates with your API key and selects an avatar with a configuration ID. Keep both out of source — read them from the environment:

export OJIN_API_KEY="…"      # from your Ojin account
export OJIN_CONFIG_ID="…"    # the persona / avatar configuration to drive

import os
from ojin.stv import OjinSTVClient

client = OjinSTVClient(
    api_key=os.environ["OJIN_API_KEY"],
    config_id=os.environ["OJIN_CONFIG_ID"],
)

Or let the SDK read and validate them for you — resolve_credentials() loads an optional .env file and raises a MissingCredentialsError (with setup instructions) if either value is absent:

from ojin import resolve_credentials
from ojin.stv import OjinSTVClient

creds = resolve_credentials()  # reads OJIN_API_KEY + OJIN_CONFIG_ID (and a .env file)
client = OjinSTVClient(api_key=creds.api_key, config_id=creds.config_id)

By default the client connects to wss://models.ojin.ai/realtime. Override it with the ws_url argument if you're pointed at another environment.

Run it server-side. The realtime transport is a WebSocket built for server-to-server delivery over a stable connection — run the client on your backend (not an end-user device), ideally in US East near Ojin's inference, and relay the final media to your users over a realtime transport such as WebRTC.

---

Quickstart

Feed the avatar one utterance of TTS audio and consume the synced stream it speaks back.

import asyncio
import os
import wave

from ojin.stv import OjinSTVClient, STVEvent, STVAudioFrame, STVVideoFrame


async def main() -> None:
    ready = asyncio.Event()
    done = asyncio.Event()

    async with OjinSTVClient(
        api_key=os.environ["OJIN_API_KEY"],
        config_id=os.environ["OJIN_CONFIG_ID"],
    ) as client:
        # Events may be sync or async; register with a decorator or add_listener().
        client.add_listener(STVEvent.SESSION_READY, lambda **_: ready.set())
        client.add_listener(STVEvent.BOT_STOPPED_SPEAKING, lambda **_: done.set())

        @client.on(STVEvent.ERROR)
        def _on_error(message: str, **_):
            print("ojin error:", message)

        # Wait until the avatar session is live (race-free: skip if already up).
        if not client.is_connected:
            await ready.wait()

        # Load mono int16 PCM TTS audio at ANY sample rate — the SDK resamples it.
        # The PCM is treated as a single channel and is NOT downmixed, so feed mono
        # audio (downmix stereo to mono before sending).
        with wave.open("hello.wav", "rb") as wav:  # a mono WAV
            await client.say(
                wav.readframes(wav.getnframes()),
                sample_rate=wav.getframerate(),
                num_channels=1,
            )

        # Consume the synchronized 25 fps audio + video stream.
        async def consume() -> None:
            async for frame in client.output_stream():
                if isinstance(frame, STVVideoFrame) and frame.rgb is not None:
                    handle_video(frame)  # frame.rgb = width*height*3 RGB bytes
                elif isinstance(frame, STVAudioFrame):
                    handle_audio(frame)  # frame.pcm = int16 PCM @ frame.sample_rate

        consumer = asyncio.create_task(consume())
        await done.wait()           # avatar finished the turn
        await asyncio.sleep(0.5)    # let the tail frames drain
        consumer.cancel()


asyncio.run(main())

say() is a one-shot helper for start_turn() + send_tts_audio(). For a live agent you'll call start_turn() once per utterance and stream chunks with send_tts_audio() as your TTS produces them.

---

Core concepts

Turns. A turn is one spoken utterance. Open it with start_turn(), then push audio with send_tts_audio(pcm, sample_rate, num_channels) as many times as you like. The client buffers and plays the original audio you sent while a 16 kHz copy goes to the server for lip-sync — so the voice the user hears is always exactly yours. Because the original is what's played back, you can feed higher-quality TTS (e.g. 24 kHz) for better sound and lip-sync still works on the 16 kHz copy — just set your player to the sample_rate each STVAudioFrame reports.

Input shaping. Feed audio at whatever cadence your TTS produces — even tiny 40 ms fragments. The client takes care of the input shape to optimize latency and stability: it primes a ~1 s lead after each start_turn(), then combines your audio into ≥400 ms chunks before forwarding it to the server, so the inference head never starves and lip-sync stays stable. It's automatic — tune it (or restore per-chunk sends) with the server_feed_* fields on STVConfig.

Audio is the clock. The playback loop emits exactly one audio frame every tick (real audio or silence so the consumer never starves) plus a video frame whenever one is ready, at STVConfig.fps (default 25 → a 40 ms tick). Video falls back to repeating the last frame rather than stalling.

Interruption (barge-in). Call interrupt() to cut a turn mid-sentence. The client fades the current audio, cancels the in-flight inference server-side, and re-syncs cleanly for the next turn. The INTERRUPTED event fires when a barge-in is accepted.

Output sink. By default frames land in a QueueOutput you drain with output_stream(). Inject a custom STVOutput (e.g. to push straight into a media transport) and consume it directly — output_stream() is only for the default queue.

Events

Register handlers with @client.on(STVEvent.X) or client.add_listener(STVEvent.X, cb). Handlers may be sync or async, and a failing handler never breaks the playback loop.

Event	Fires when	Handler kwargs
SESSION_READY	The session is live and ready for audio	session_data: dict | None
BOT_STARTED_SPEAKING	The first speech frame of a turn is played	—
BOT_STOPPED_SPEAKING	A turn has finished playing	—
INTERRUPTED	A barge-in was accepted	—
ERROR	A transport or server error occurred	message: str, code: str (server only), fatal: bool
CLOSED	The session has been torn down	—

---

Recipes

Render an utterance to MP4

The [stv] extra already ships OpenCV, so a few lines turn the RGB stream into a video file.

import asyncio
import os
import wave

import cv2
import numpy as np

from ojin.stv import OjinSTVClient, STVEvent, STVVideoFrame

FPS = 25


async def render(wav_path: str, out_path: str) -> None:
    ready, done = asyncio.Event(), asyncio.Event()
    writer = None  # created on the first frame, sized to whatever the server sends

    async with OjinSTVClient(
        api_key=os.environ["OJIN_API_KEY"],
        config_id=os.environ["OJIN_CONFIG_ID"],
    ) as client:
        client.add_listener(STVEvent.SESSION_READY, lambda **_: ready.set())
        client.add_listener(STVEvent.BOT_STOPPED_SPEAKING, lambda **_: done.set())
        if not client.is_connected:
            await ready.wait()

        with wave.open(wav_path, "rb") as wav:  # mono int16 PCM
            await client.say(
                wav.readframes(wav.getnframes()),
                sample_rate=wav.getframerate(),
                num_channels=1,
            )

        async def consume() -> None:
            nonlocal writer
            async for frame in client.output_stream():
                if isinstance(frame, STVVideoFrame) and frame.rgb is not None:
                    if writer is None:  # size the file to the server's native frame
                        writer = cv2.VideoWriter(
                            out_path,
                            cv2.VideoWriter_fourcc(*"mp4v"),
                            FPS,
                            (frame.width, frame.height),
                        )
                    rgb = np.frombuffer(frame.rgb, np.uint8)
                    rgb = rgb.reshape(frame.height, frame.width, 3)
                    writer.write(cv2.cvtColor(rgb, cv2.COLOR_RGB2BGR))

        consumer = asyncio.create_task(consume())
        await done.wait()
        await asyncio.sleep(0.5)
        consumer.cancel()

    if writer is not None:
        writer.release()


asyncio.run(render("hello.wav", "avatar.mp4"))

The MP4 above has no audio track — STVAudioFrame.pcm carries the synced audio if you want to mux it back in with ffmpeg.

Interrupt a turn (barge-in)

await client.say(long_intro_pcm, sample_rate=24000, num_channels=1)
# …user starts talking…
await client.interrupt()           # fade + server-side cancel
await client.say(reply_pcm, sample_rate=24000, num_channels=1)  # next turn re-syncs

Swap the internals

Everything cross-cutting is injected behind a small protocol, so you can tune or replace it without touching the client.

from ojin.stv import (
    OjinSTVClient,
    STVConfig,
    SoxrResampler,
    PassthroughDecoder,
)

client = OjinSTVClient(
    api_key=os.environ["OJIN_API_KEY"],
    config_id=os.environ["OJIN_CONFIG_ID"],
    config=STVConfig(fps=25, interrupt_audio_fade_s=0.5),
    resampler=SoxrResampler(),       # or NumpyLinearResampler() for zero native deps
    decoder=PassthroughDecoder(),    # skip JPEG decode; read frame.source_bytes yourself
)

With a PassthroughDecoder, STVVideoFrame.rgb is None and the raw JPEG arrives in STVVideoFrame.source_bytes — ideal when you forward frames to a browser or transport that decodes them itself.

---

Configuration

STVConfig holds the behavioral knobs (connection identity stays on the client constructor):

Field	Default	What it does
client_connect_max_retries	3	Connect attempts before giving up
client_reconnect_delay	3.0	Seconds between connect attempts
fps	25	Playback frame rate (40 ms tick)
initial_buffer_frames	6	Video frames buffered before playback starts (the small jitter buffer)
max_buffered_video_frames	700	Hard cap on queued video frames
align_audio_on_swap	True	Re-align audio/video at buffer swaps
interrupt_audio_fade_s	0.75	Fade length applied on barge-in
lipsync_trace_enabled	False	Emit the per-tick A/V-sync diagnostics
server_feed_batching_enabled	True	Prime + combine the server-bound audio feed (False = send each chunk as-is)
server_feed_initial_chunk_ms	1000	Initial lead accumulated after each start_turn()
server_feed_min_chunk_ms	400	Steady-state minimum send size
server_feed_flush_idle_ms	200	Quiet time before flushing a sub-threshold tail

Video frames are emitted at the server's native resolution — read STVVideoFrame.width/height per frame rather than configuring an output size. Set OJIN_MODE=dev in the environment to attach the dev-mode query flag when connecting with the default transport.

---

Low-level client

OjinClient is a thin async WebSocket wrapper over the Ojin wire protocol. You own the loop: connect, wait for the session, send 16 kHz mono int16 PCM, and read frames.

import asyncio
import os

from ojin.entities.interaction_messages import ErrorResponseMessage
from ojin.ojin_client import OjinClient
from ojin.ojin_client_messages import (
    OjinAudioInputMessage,
    OjinSessionReadyMessage,
    OjinInteractionResponseMessage,
)


async def main(pcm_16k_mono: bytes) -> None:
    client = OjinClient(
        ws_url="wss://models.ojin.ai/realtime",
        api_key=os.environ["OJIN_API_KEY"],
        config_id=os.environ["OJIN_CONFIG_ID"],
    )
    await client.connect()

    # The server announces readiness before it will accept input.
    while True:
        msg = await client.receive_message()
        if isinstance(msg, OjinSessionReadyMessage):
            break
        if isinstance(msg, ErrorResponseMessage):
            raise RuntimeError(msg.payload.message)  # e.g. auth / capacity error

    await client.start_interaction()
    await client.send_message(OjinAudioInputMessage(audio_int16_bytes=pcm_16k_mono))

    # Each response carries one JPEG video frame + the int16 PCM it was synced to.
    while True:
        msg = await client.receive_message()
        if isinstance(msg, OjinInteractionResponseMessage):
            jpeg_bytes = msg.video_frame_bytes
            pcm_bytes = msg.audio_frame_bytes
            frame_type = msg.frame_type  # FrameType: IDLE / SPEECH / FADE_OUT / START_OF_SPEECH
            ...
            if msg.is_final_response:
                break

    await client.close()

Frame types (ojin.ojin_client_messages.FrameType): IDLE = 0, SPEECH = 1, FADE_OUT = 2, START_OF_SPEECH = 3.

Send these: OjinAudioInputMessage, OjinTextInputMessage, OjinCancelInteractionMessage, OjinEndInteractionMessage. Receive these: OjinSessionReadyMessage, OjinInteractionResponseMessage (from ojin.ojin_client_messages), and ErrorResponseMessage (from ojin.entities.interaction_messages).

Send audio in large chunks. Push as much audio as possible upfront (at least ~1 s), then keep a steady 25 fps input timeline with the biggest chunks you can. Feeding tiny inputs leaves the server unable to sustain speech at 25 fps, so it emits still ("idle") frames in between. The high-level OjinSTVClient manages this for you.

---

Integrations

• Pipecat — this SDK is the engine behind Ojin's OjinVideoService for Pipecat. OjinSTVClient exposes the same behavior with no Pipecat dependency, so you can adopt it directly.
• LiveKit Agents / custom transports — feed send_tts_audio() from your TTS and push STVVideoFrame / STVAudioFrame into any media pipeline. Inject a custom STVOutput to write straight into your transport.
• WebRTC (roadmap) — the transport sits behind the IOjinClient protocol; a WebRTC transport can be dropped in without touching OjinSTVClient.

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Troubleshooting

• No backend servers available — capacity is momentarily exhausted; retry shortly. Surfaced as an ERROR event with code NO_BACKEND_SERVER_AVAILABLE.
• Avatar mouth stays still / only idle frames — the server is starved of audio and can't sustain 25 fps speech, so it emits idle frames in between. OjinSTVClient shapes the input to prevent this (see Input shaping above); it should only surface if you set server_feed_batching_enabled=False or drive the low-level OjinClient — then send a ~1 s lead up front, followed by the largest chunks you can.
• Inference Server is not ready (low-level) — wait for OjinSessionReadyMessage before calling send_message().
• Choppy playback — keep the event loop free; the SDK already decodes JPEG off-loop, but heavy synchronous work in your frame handlers will stall the 40 ms tick. Enable STVConfig(lipsync_trace_enabled=True) to inspect per-tick timing.
• Latency higher than expected — the WebSocket transport is built for server-to-server use over a stable connection. Run the client on a backend (not an end-user device), ideally in US East, close to Ojin's inference; deliver the final media to end users over a realtime transport such as WebRTC. The client keeps a small video buffer (initial_buffer_frames) to absorb network jitter, since the server delivers at realtime 25 fps.

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Documentation & support

• 📚 Full docs: docs.ojin.ai
• 🌐 Platform & pricing: ojin.ai ($10 free credits to start)
• 🐛 Issues & feature requests: github.com/ojinai/python-sdk/issues
• 🤝 Contributing: see CONTRIBUTING.md

License

Apache License 2.0 — see LICENSE.