Bidirectional streaming using the Gemini Live API


The Gemini Live API enables low-latency bidirectional text and voice interactions with Gemini. Using the Live API, you can provide end users with the experience of natural, human-like voice conversations, with the ability to interrupt the model's responses using text or voice commands. The model can process text and audio input (video coming soon!), and it can provide text and audio output.

You can prototype with prompts and the Live API in Vertex AI Studio.

The Live API is a stateful API that creates a WebSocket connection to establish a session between the client and the Gemini server. For details, see the Live API reference documentation.

Before you begin

Only available when using the Vertex AI Gemini API as your API provider.

If you haven't already, complete the getting started guide, which describes how to set up your Firebase project, connect your app to Firebase, add the SDK, initialize the backend service for the Vertex AI Gemini API, and create a LiveModel instance.

Models that support this capability

The Live API is supported by gemini-2.0-flash-live-preview-04-09 only (not gemini-2.0-flash).

Use the standard features of the Live API

This section describes how to use the standard features of the Live API, specifically to stream various types of inputs and outputs:

Generate streamed text from streamed text input

Before trying this sample, complete the Before you begin section of this guide to set up your project and app.
In that section, you'll also click a button for your chosen Gemini API provider so that you see provider-specific content on this page.

You can send streamed text input and receive streamed text output. Make sure to create a liveModel instance and set the response modality to Text.

Swift

The Live API is not yet supported for Apple platform apps, but check back soon!

Kotlin

// Initialize the Vertex AI Gemini API backend service
// Create a `LiveModel` instance with the model that supports the Live API
val model = Firebase.ai(backend = GenerativeBackend.vertexAI()).liveModel(
    modelName = "gemini-2.0-flash-live-preview-04-09",
    // Configure the model to respond with text
    generationConfig = liveGenerationConfig {
        responseModality = ResponseModality.TEXT 
   }
)

val session = model.connect()

// Provide a text prompt
val text = "tell a short story"

session.send(text)

var outputText = ""
session.receive().collect {
    if(it.status == Status.TURN_COMPLETE) {
        // Optional: if you don't require to send more requests.
        session.stopReceiving();
    }
    outputText = outputText + it.text
}

// Output received from the server.
println(outputText)

Java

ExecutorService executor = Executors.newFixedThreadPool(1);
// Initialize the Vertex AI Gemini API backend service
// Create a `LiveModel` instance with the model that supports the Live API
LiveGenerativeModel lm = FirebaseAI.getInstance(GenerativeBackend.vertexAI()).liveModel(
        "gemini-2.0-flash-live-preview-04-09",
        // Configure the model to respond with text
        new LiveGenerationConfig.Builder()
                .setResponseModalities(ResponseModality.TEXT)
                .build()
);
LiveModelFutures model = LiveModelFutures.from(lm);
ListenableFuture<LiveSession> sessionFuture =  model.connect();
class LiveContentResponseSubscriber implements Subscriber<LiveContentResponse> {
    @Override
    public void onSubscribe(Subscription s) {
        s.request(Long.MAX_VALUE); // Request an unlimited number of items
    }
    @Override
    public void onNext(LiveContentResponse liveContentResponse) {
       // Handle the response from the server.
	System.out.println(liveContentResponse.getText());
    }
    @Override
    public void onError(Throwable t) {
        System.err.println("Error: " + t.getMessage());
    }
    @Override
    public void onComplete() {
        System.out.println("Done receiving messages!");
    }
}
Futures.addCallback(sessionFuture, new FutureCallback<LiveSession>() {
    @Override
    public void onSuccess(LiveSession ses) {
	  LiveSessionFutures session = LiveSessionFutures.from(ses);
        // Provide a text prompt
        String text = "tell me a short story?";
        session.send(text);
        Publisher<LiveContentResponse> publisher = session.receive();
        publisher.subscribe(new LiveContentResponseSubscriber());
    }
    @Override
    public void onFailure(Throwable t) {
        // Handle exceptions
    }
}, executor);

Web

The Live API is not yet supported for Web apps, but check back soon!

Dart

import 'package:firebase_ai/firebase_ai.dart';
import 'package:firebase_core/firebase_core.dart';
import 'firebase_options.dart';

late LiveModelSession _session;

await Firebase.initializeApp(
  options: DefaultFirebaseOptions.currentPlatform,
);

// Initialize the Vertex AI Gemini API backend service
// Create a `LiveModel` instance with the model that supports the Live API
final model = FirebaseAI.vertexAI().liveModel(
  model: 'gemini-2.0-flash-live-preview-04-09',
  // Configure the model to respond with text
  config: LiveGenerationConfig(responseModalities: [ResponseModality.text]),
);

_session = await model.connect();

// Provide a text prompt
final prompt = Content.text('tell a short story');
await _session.send(input: prompt, turnComplete: true);

// In a separate thread, receive the response
await for (final message in _session.receive()) {
   // Process the received message 
}

Unity

using Firebase;
using Firebase.AI;

async Task SendTextReceiveText() {
  // Initialize the Vertex AI Gemini API backend service
  // Create a `LiveModel` instance with the model that supports the Live API
  var model = FirebaseAI.GetInstance(FirebaseAI.Backend.VertexAI()).GetLiveModel(
    modelName: "gemini-2.0-flash-live-preview-04-09",
    // Configure the model to respond with text
    liveGenerationConfig: new LiveGenerationConfig(
        responseModalities: new[] { ResponseModality.Text })
  );

  LiveSession session = await model.ConnectAsync();

  // Provide a text prompt
  var prompt = ModelContent.Text("tell a short story");
  await session.SendAsync(content: prompt, turnComplete: true);

  // Receive the response
  await foreach (var message in session.ReceiveAsync()) {
    // Process the received message
    if (!string.IsNullOrEmpty(message.Text)) {
      UnityEngine.Debug.Log("Received message: " + message.Text);
    }
  }
}

Learn how to choose a model appropriate for your use case and app.

Generate streamed audio from streamed audio input

Before trying this sample, complete the Before you begin section of this guide to set up your project and app.
In that section, you'll also click a button for your chosen Gemini API provider so that you see provider-specific content on this page.

You can send streamed audio input and receive streamed audio output. Make sure to create a LiveModel instance and set the response modality to Audio.

Learn how to configure and customize the response voice (later on this page).

Swift

The Live API is not yet supported for Apple platform apps, but check back soon!

Kotlin

// Initialize the Vertex AI Gemini API backend service
// Create a `LiveModel` instance with the model that supports the Live API
val model = Firebase.ai(backend = GenerativeBackend.vertexAI()).liveModel(
    modelName = "gemini-2.0-flash-live-preview-04-09",
    // Configure the model to respond with text
    generationConfig = liveGenerationConfig {
        responseModality = ResponseModality.AUDIO 
   }
)

val session = model.connect()

// This is the recommended way.
// However, you can create your own recorder and handle the stream.
session.startAudioConversation()

Java

ExecutorService executor = Executors.newFixedThreadPool(1);
// Initialize the Vertex AI Gemini API backend service
// Create a `LiveModel` instance with the model that supports the Live API
LiveGenerativeModel lm = FirebaseAI.getInstance(GenerativeBackend.vertexAI()).liveModel(
        "gemini-2.0-flash-live-preview-04-09",
        // Configure the model to respond with text
        new LiveGenerationConfig.Builder()
                .setResponseModalities(ResponseModality.TEXT)
                .build()
);
LiveModelFutures model = LiveModelFutures.from(lm);
ListenableFuture<LiveSession> sessionFuture =  model.connect();

Futures.addCallback(sessionFuture, new FutureCallback<LiveSession>() {
    @Override
    public void onSuccess(LiveSession ses) {
	 LiveSessionFutures session = LiveSessionFutures.from(ses);
        session.startAudioConversation();
    }
    @Override
    public void onFailure(Throwable t) {
        // Handle exceptions
    }
}, executor);

Web

The Live API is not yet supported for Web apps, but check back soon!

Dart

import 'package:firebase_ai/firebase_ai.dart';
import 'package:firebase_core/firebase_core.dart';
import 'firebase_options.dart';
import 'package:your_audio_recorder_package/your_audio_recorder_package.dart';

late LiveModelSession _session;
final _audioRecorder = YourAudioRecorder();

await Firebase.initializeApp(
  options: DefaultFirebaseOptions.currentPlatform,
);

// Initialize the Vertex AI Gemini API backend service
// Create a `LiveModel` instance with the model that supports the Live API
final model = FirebaseAI.vertexAI().liveModel(
  model: 'gemini-2.0-flash-live-preview-04-09',
   // Configure the model to respond with audio
   config: LiveGenerationConfig(responseModalities: [ResponseModality.audio]),
);

_session = await model.connect();

final audioRecordStream = _audioRecorder.startRecordingStream();
// Map the Uint8List stream to InlineDataPart stream
final mediaChunkStream = audioRecordStream.map((data) {
  return InlineDataPart('audio/pcm', data);
});
await _session.startMediaStream(mediaChunkStream);

// In a separate thread, receive the audio response from the model
await for (final message in _session.receive()) {
   // Process the received message 
}

Unity

using Firebase;
using Firebase.AI;

async Task SendTextReceiveAudio() {
  // Initialize the Vertex AI Gemini API backend service
  // Create a `LiveModel` instance with the model that supports the Live API
  var model = FirebaseAI.GetInstance(FirebaseAI.Backend.VertexAI()).GetLiveModel(
    modelName: "gemini-2.0-flash-live-preview-04-09",
    // Configure the model to respond with audio
    liveGenerationConfig: new LiveGenerationConfig(
        responseModalities: new[] { ResponseModality.Audio })
  );

  LiveSession session = await model.ConnectAsync();

  // Start a coroutine to send audio from the Microphone
  var recordingCoroutine = StartCoroutine(SendAudio(session));

  // Start receiving the response
  await ReceiveAudio(session);
}

IEnumerator SendAudio(LiveSession liveSession) {
  string microphoneDeviceName = null;
  int recordingFrequency = 16000;
  int recordingBufferSeconds = 2;

  var recordingClip = Microphone.Start(microphoneDeviceName, true,
                                       recordingBufferSeconds, recordingFrequency);

  int lastSamplePosition = 0;
  while (true) {
    if (!Microphone.IsRecording(microphoneDeviceName)) {
      yield break;
    }

    int currentSamplePosition = Microphone.GetPosition(microphoneDeviceName);

    if (currentSamplePosition != lastSamplePosition) {
      // The Microphone uses a circular buffer, so we need to check if the
      // current position wrapped around to the beginning, and handle it
      // accordingly.
      int sampleCount;
      if (currentSamplePosition > lastSamplePosition) {
        sampleCount = currentSamplePosition - lastSamplePosition;
      } else {
        sampleCount = recordingClip.samples - lastSamplePosition + currentSamplePosition;
      }

      if (sampleCount > 0) {
        // Get the audio chunk
        float[] samples = new float[sampleCount];
        recordingClip.GetData(samples, lastSamplePosition);

        // Send the data, discarding the resulting Task to avoid the warning
        _ = liveSession.SendAudioAsync(samples);

        lastSamplePosition = currentSamplePosition;
      }
    }

    // Wait for a short delay before reading the next sample from the Microphone
    const float MicrophoneReadDelay = 0.5f;
    yield return new WaitForSeconds(MicrophoneReadDelay);
  }
}

Queue audioBuffer = new();

async Task ReceiveAudio(LiveSession liveSession) {
  int sampleRate = 24000;
  int channelCount = 1;

  // Create a looping AudioClip to fill with the received audio data
  int bufferSamples = (int)(sampleRate * channelCount);
  AudioClip clip = AudioClip.Create("StreamingPCM", bufferSamples, channelCount,
                                    sampleRate, true, OnAudioRead);

  // Attach the clip to an AudioSource and start playing it
  AudioSource audioSource = GetComponent();
  audioSource.clip = clip;
  audioSource.loop = true;
  audioSource.Play();

  // Start receiving the response
  await foreach (var message in liveSession.ReceiveAsync()) {
    // Process the received message
    foreach (float[] pcmData in message.AudioAsFloat) {
      lock (audioBuffer) {
        foreach (float sample in pcmData) {
          audioBuffer.Enqueue(sample);
        }
      }
    }
  }
}

// This method is called by the AudioClip to load audio data.
private void OnAudioRead(float[] data) {
  int samplesToProvide = data.Length;
  int samplesProvided = 0;

  lock(audioBuffer) {
    while (samplesProvided < samplesToProvide && audioBuffer.Count > 0) {
      data[samplesProvided] = audioBuffer.Dequeue();
      samplesProvided++;
    }
  }

  while (samplesProvided < samplesToProvide) {
    data[samplesProvided] = 0.0f;
    samplesProvided++;
  }
}

Learn how to choose a model appropriate for your use case and app.



Create more engaging and interactive experiences

This section describes how to create and manage more engaging or interactive features of the Live API.

Change the response voice

The Live API uses Chirp 3 to support synthesized speech responses. When using Firebase AI Logic, you can send audio in 5 HD voices and 31 languages.

If you don't specify a voice, the default is Puck. Alternatively, you can configure the model to respond in any of the following voices:

Aoede (female)
Charon (male)
Fenrir (male)
Kore (female)
Puck (male)

For demos of what these voices sound like and for the full list of available languages, see Chirp 3: HD voices.

To specify a voice, set the voice name within the speechConfig object as part of the model configuration:

Swift

The Live API is not yet supported for Apple platform apps, but check back soon!

Kotlin

// ...

val model = Firebase.ai(backend = GenerativeBackend.vertexAI()).liveModel(
    modelName = "gemini-2.0-flash-live-preview-04-09",
    // Configure the model to use a specific voice for its audio response
    generationConfig = liveGenerationConfig {
        responseModality = ResponseModality.AUDIO
        speechConfig = SpeechConfig(voice = Voices.FENRIR)
    }
)

// ...

Java

// ...

LiveModel model = FirebaseAI.getInstance(GenerativeBackend.vertexAI()).liveModel(
    "gemini-2.0-flash-live-preview-04-09",
    // Configure the model to use a specific voice for its audio response
    new LiveGenerationConfig.Builder()
        .setResponseModalities(ResponseModality.AUDIO)
        .setSpeechConfig(new SpeechConfig(Voices.FENRIR))
        .build()
);

// ...

Web

The Live API is not yet supported for Web apps, but check back soon!

Dart

// ...

final model = FirebaseVertexAI.instance.liveModel(
  model: 'gemini-2.0-flash-live-preview-04-09',
  // Configure the model to use a specific voice for its audio response
  config: LiveGenerationConfig(
    responseModality: ResponseModality.audio,
    speechConfig: SpeechConfig(voice: Voice.fenrir),
  ),
);

// ...

Unity

Snippets coming soon!

For the best results when prompting and requiring the model to respond in a non-English language, include the following as part of your system instructions:

RESPOND IN LANGUAGE. YOU MUST RESPOND UNMISTAKABLY IN LANGUAGE.

Maintain context across sessions and requests

You can use a chat structure to maintain context across sessions and requests. Note that this only works for text input and text output.

This approach is best for short contexts; you can send turn-by-turn interactions to represent the exact sequence of events . For longer contexts, we recommend providing a single message summary to free up the context window for subsequent interactions.

Handle interruptions

Firebase AI Logic does not yet support handling interruptions. Check back soon!

Use function calling (tools)

You can define tools, like available functions, to use with the Live API just like you can with the standard content generation methods. This section describes some nuances when using the Live API with function calling. For a complete description and examples for function calling, see the function calling guide.

From a single prompt, the model can generate multiple function calls and the code necessary to chain their outputs. This code executes in a sandbox environment, generating subsequent BidiGenerateContentToolCall messages. The execution pauses until the results of each function call are available, which ensures sequential processing.

Additionally, using the Live API with function calling is particularly powerful because the model can request follow-up or clarifying information from the user. For example, if the model doesn't have enough information to provide a parameter value to a function it wants to call, then the model can ask the user to provide more or clarifying information.

The client should respond with BidiGenerateContentToolResponse.



Limitations and requirements

Keep in mind the following limitations and requirements of the Live API.

Transcription

Firebase AI Logic does not yet support transcriptions. Check back soon!

Languages

Audio formats

The Live API supports the following audio formats:

  • Input audio format: Raw 16 bit PCM audio at 16kHz little-endian
  • Output audio format: Raw 16 bit PCM audio at 24kHz little-endian

Rate limits

The following rate limits apply:

  • 10 concurrent sessions per Firebase project
  • 4M tokens per minute

Session length

The default length for a session is 30 minutes. When the session duration exceeds the limit, the connection is terminated.

The model is also limited by the context size. Sending large chunks of input may result in earlier session termination.

Voice activity detection (VAD)

The model automatically performs voice activity detection (VAD) on a continuous audio input stream. VAD is enabled by default.

Token counting

You cannot use the CountTokens API with the Live API.


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