feat: Add Camb.ai TTS plugin for LiveKit Agents

- Implement TTS class with streaming audio synthesis
- Support MARS models (mars-8, mars-8-flash, mars-8-instruct)
- Add voice listing functionality via list_voices()
- Support configurable voice parameters (speed, language, voice_id)
- Include PCM, WAV, FLAC, and ADTS output formats
- Add examples and documentation

Author: eRuaro

livekit-plugins/livekit-plugins-camb/README.md

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+# Camb.ai Plugin for LiveKit Agents
+
+Text-to-Speech plugin for [Camb.ai](https://camb.ai) TTS API, powered by MARS-8 technology.
+
+## Features
+
+- High-quality neural text-to-speech with MARS-8 series models
+- Multiple model variants (mars-8, mars-8-flash, mars-8-instruct)
+- User instructions for style and tone control
+- Speed control and enhanced pronunciation
+- Support for 140+ languages
+- Real-time HTTP streaming
+- Pre-built voice library
+
+## Installation
+
+```bash
+pip install livekit-plugins-camb
+```
+
+## Prerequisites
+
+You'll need a Camb.ai API key. Set it as an environment variable:
+
+```bash
+export CAMB_API_KEY=your_api_key_here
+```
+
+Or obtain it from [Camb.ai Studio](https://studio.camb.ai/public/onboarding).
+
+## Quick Start
+
+```python
+from livekit.plugins.camb import TTS
+
+# Initialize TTS (uses CAMB_API_KEY env var)
+tts = TTS()
+
+# Synthesize speech
+stream = tts.synthesize("Hello from Camb.ai!")
+audio_frame = await stream.collect()
+
+# Save to file
+with open("output.wav", "wb") as f:
+    f.write(audio_frame.to_wav_bytes())
+```
+
+## List Available Voices
+
+```python
+from livekit.plugins.camb import list_voices
+
+voices = await list_voices()
+for voice in voices:
+    print(f"{voice.name} ({voice.id}): {voice.gender}, {voice.language}")
+```
+
+## Select a Specific Voice
+
+```python
+tts = TTS(voice_id=2681)  # Use Attic voice
+stream = tts.synthesize("Using a specific voice!")
+```
+
+## Model Selection
+
+Camb.ai offers multiple MARS-8 models for different use cases:
+
+```python
+# Default balanced model
+tts = TTS(model="mars-8")
+
+# Faster inference
+tts = TTS(model="mars-8-flash")
+
+# Supports user instructions for style/tone
+tts = TTS(
+    model="mars-8-instruct",
+    user_instructions="Speak in a friendly, conversational tone"
+)
+```
+
+## Advanced Configuration
+
+```python
+tts = TTS(
+    api_key="your-api-key",  # Or use CAMB_API_KEY env var
+    voice_id=2681,  # Voice ID from list-voices (Attic voice)
+    language="en-us",  # BCP-47 locale
+    model="mars-8-instruct",  # MARS model variant
+    speed=1.0,  # Speech rate (0.5-2.0)
+    user_instructions="Speak energetically with clear enunciation",
+    output_format="pcm_s16le",  # Audio format
+    enhance_named_entities=True,  # Better pronunciation for names/places
+)
+```
+
+## Usage with LiveKit Agents
+
+```python
+from livekit import agents
+from livekit.plugins.camb import TTS
+
+async def entrypoint(ctx: agents.JobContext):
+    # Connect to room
+    await ctx.connect()
+
+    # Initialize TTS
+    tts = TTS(language="en-us", speed=1.1)
+
+    # Synthesize and publish
+    stream = tts.synthesize("Hello from LiveKit with Camb.ai!")
+    audio_frame = await stream.collect()
+
+    # Publish to room
+    source = agents.AudioSource(tts.sample_rate, tts.num_channels)
+    track = agents.LocalAudioTrack.create_audio_track("tts", source)
+    await ctx.room.local_participant.publish_track(track)
+    await source.capture_frame(audio_frame)
+```
+
+## Configuration Options
+
+### TTS Constructor Parameters
+
+- **api_key** (str | None): Camb.ai API key
+- **voice_id** (int): Voice ID to use (default: 2681)
+- **language** (str): BCP-47 locale (default: "en-us")
+- **model** (SpeechModel): MARS model variant (default: "mars-8")
+- **speed** (float): Speech rate (default: 1.0)
+- **user_instructions** (str | None): Style/tone guidance (requires mars-8-instruct)
+- **output_format** (OutputFormat): Audio format (default: "pcm_s16le")
+- **enhance_named_entities** (bool): Enhanced pronunciation (default: False)
+- **base_url** (str): API base URL
+- **http_session** (aiohttp.ClientSession | None): Reusable HTTP session
+
+### Available Models
+
+- **mars-8**: Default, balanced quality and speed
+- **mars-8-flash**: Faster inference, lower latency
+- **mars-8-instruct**: Supports user_instructions for style control
+- **mars-7**: Previous generation model
+- **mars-6**: Older generation model
+- **auto**: Automatic model selection
+
+### Output Formats
+
+- **pcm_s16le**: 16-bit PCM (recommended for streaming)
+- **pcm_s32le**: 32-bit PCM (highest quality)
+- **wav**: WAV with headers
+- **flac**: Lossless compression
+- **adts**: ADTS streaming format
+
+## API Reference
+
+### TTS Class
+
+Main text-to-speech interface.
+
+**Methods:**
+- `synthesize(text: str) -> ChunkedStream`: Synthesize text to speech
+- `update_options(**kwargs)`: Update voice settings dynamically
+- `aclose()`: Clean up resources
+
+**Properties:**
+- `model` (str): Current MARS model name
+- `provider` (str): Provider name ("Camb.ai")
+- `sample_rate` (int): Audio sample rate (24000 Hz)
+- `num_channels` (int): Number of audio channels (1)
+
+### list_voices Function
+
+```python
+async def list_voices(
+    api_key: str | None = None,
+    base_url: str = "https://client.camb.ai/apis",
+) -> list[VoiceInfo]
+```
+
+Returns list of available voices with metadata.
+
+### VoiceInfo
+
+Voice metadata object with:
+- **id** (int): Unique voice identifier
+- **name** (str): Human-readable voice name
+- **gender** (str | None): Voice gender
+- **language** (str | None): BCP-47 locale
+
+## Multi-Language Support
+
+Camb.ai supports 140+ languages. Specify using BCP-47 locales:
+
+```python
+# French
+tts = TTS(language="fr-fr", voice_id=...)
+
+# Spanish
+tts = TTS(language="es-es", voice_id=...)
+
+# Japanese
+tts = TTS(language="ja-jp", voice_id=...)
+```
+
+## Dynamic Options
+
+Update TTS settings without recreating the instance:
+
+```python
+tts = TTS()
+
+# Change voice
+tts.update_options(voice_id=12345)
+
+# Change speed and model
+tts.update_options(speed=1.2, model="mars-8-flash")
+
+# Add user instructions
+tts.update_options(
+    model="mars-8-instruct",
+    user_instructions="Speak warmly and enthusiastically"
+)
+```
+
+## Error Handling
+
+The plugin handles errors according to LiveKit conventions:
+
+```python
+from livekit.agents import APIStatusError, APIConnectionError, APITimeoutError
+
+try:
+    stream = tts.synthesize("Hello!")
+    audio = await stream.collect()
+except APIStatusError as e:
+    print(f"API error: {e.status_code} - {e.message}")
+except APIConnectionError as e:
+    print(f"Connection error: {e}")
+except APITimeoutError as e:
+    print(f"Request timed out: {e}")
+```
+
+## Future Features
+
+Coming soon:
+- GCP Vertex AI integration
+- Voice cloning via custom voice creation
+- Voice generation from text descriptions
+- WebSocket streaming for real-time applications
+
+## Links
+
+- [Camb.ai Documentation](https://camb.mintlify.app/)
+- [LiveKit Agents Documentation](https://docs.livekit.io/agents/)
+- [GitHub Repository](https://github.com/livekit/agents)
+
+## License
+
+Apache License 2.0