NullFilter

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Overview

NullFilter is a filtering processor that blocks all frames from passing through, with the exception of system frames and end frames which are required for proper pipeline operation.

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Constructor Parameters

The NullFilter constructor accepts no specific parameters beyond those inherited from FrameProcessor.

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Functionality

When a frame passes through the processor:

• If the frame is a SystemFrame or EndFrame, it is passed through
• All other frame types are blocked and do not continue through the pipeline

This filter effectively acts as a barrier that allows only the essential system frames required for pipeline initialization, shutdown, and management.

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Use Cases

NullFilter is useful in several scenarios:

• Temporarily disabling parts of a pipeline without removing components
• Creating dead-end branches in parallel pipelines
• Testing pipeline behavior with blocked communication
• Implementing conditional pipelines where certain paths should be blocked

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Usage Example

from pipecat.processors.filters import NullFilter

# Create a null filter that blocks all non-system frames
blocker = NullFilter()

# Add to pipeline
pipeline = Pipeline([
    source,
    blocker,  # Blocks all regular frames
    destination  # Will only receive system frames
])

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Frame Flow

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Notes

• Blocks all regular frames in both directions
• Only allows system frames and end frames to pass through
• Useful for testing, debugging, and creating conditional pipelines
• Minimal overhead as it performs simple type checking
• Can be used to temporarily disable parts of a pipeline