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Overview

STTMuteFilter is a general-purpose processor that combines STT muting and interruption control. When active, it prevents both transcription and interruptions during specified conditions (e.g., bot speech, function calls), providing a cleaner conversation flow.

The processor supports multiple simultaneous strategies for when to mute the STT service, making it flexible for different use cases.

Want to try it out? Check out the STTMuteFilter foundational demo

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Constructor Parameters

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stt_service
STTService
required

The STT service to control

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config
STTMuteConfig
required

Configuration object that defines the muting strategies and optional custom logic

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Configuration

The processor is configured using STTMuteConfig, which determines when and how the STT service should be muted:

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strategies
set[STTMuteStrategy]

Set of muting strategies to apply

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should_mute_callback
Callable[[STTMuteFilter], Awaitable[bool]]
default: "None"

Optional callback for custom muting logic (required when strategy is CUSTOM)

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Muting Strategies

STTMuteConfig accepts a set of these STTMuteStrategy values:

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FIRST_SPEECH
STTMuteStrategy

Mute only during the bot’s first speech (typically during introduction)

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FUNCTION_CALL
STTMuteStrategy

Mute during LLM function calls (e.g., API requests, external service calls)

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ALWAYS
STTMuteStrategy

Mute during all bot speech

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CUSTOM
STTMuteStrategy

Use custom logic provided via callback to determine when to mute

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Input Frames

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BotStartedSpeakingFrame
Frame

Indicates bot has started speaking

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BotStoppedSpeakingFrame
Frame

Indicates bot has stopped speaking

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FunctionCallInProgressFrame
Frame

Indicates a function call has started

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FunctionCallResultFrame
Frame

Indicates a function call has completed

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StartInterruptionFrame
Frame

User interruption start event (suppressed when muted)

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StopInterruptionFrame
Frame

User interruption stop event (suppressed when muted)

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UserStartedSpeakingFrame
Frame

Indicates user has started speaking (suppressed when muted)

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UserStoppedSpeakingFrame
Frame

Indicates user has stopped speaking (suppressed when muted)

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Output Frames

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STTMuteFrame
Frame

Control frame to mute/unmute the STT service

All input frames are passed through except VAD-related frames (interruptions and user speaking events) when muted.

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Usage Examples

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Basic Usage (Mute During First Speech)

stt = DeepgramSTTService(api_key=os.getenv("DEEPGRAM_API_KEY"))
stt_mute_filter = STTMuteFilter(
    stt_service=stt,
    config=STTMuteConfig(strategies={
        STTMuteStrategy.FIRST_SPEECH
    })
)

pipeline = Pipeline([
    transport.input(),
    stt_mute_filter,  # Add before STT service
    stt,
    # ... rest of pipeline
])

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Always Mute During Bot Speech

stt_mute_filter = STTMuteFilter(
    stt_service=stt,
    config=STTMuteConfig(strategies={STTMuteStrategy.ALWAYS})
)

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Custom Muting Logic with Function Calls

async def custom_mute_logic(processor: STTMuteFilter) -> bool:
    # Example: Mute during business hours only
    current_hour = datetime.now().hour
    return processor._bot_is_speaking and (9 <= current_hour < 17)

stt_mute_filter = STTMuteFilter(
    stt_service=stt,
    config=STTMuteConfig(
        strategies={
            STTMuteStrategy.CUSTOM,
            STTMuteStrategy.FUNCTION_CALL
        },
        should_mute_callback=custom_mute_logic
    )
)

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Frame Flow

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Notes

  • Combines STT muting and interruption control into a single concept
  • Muting prevents both transcription and interruptions
  • Multiple strategies can be active simultaneously
  • Custom strategy allows for complex muting logic
  • Placed before STT service in pipeline
  • Maintains conversation flow during bot speech and function calls
  • Efficient state tracking for minimal overhead
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