NullFilter

Processor that blocks all frames except system frames

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.

Constructor Parameters

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

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.

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

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
])

Frame Flow

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