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Overview

FunctionFilter is a flexible processor that uses a custom async function to determine which frames to pass through. This allows for complex, dynamic filtering logic beyond simple type checking.

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Constructor Parameters

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filter
Callable[[Frame], Awaitable[bool]]
required
Async function that examines each frame and returns True to allow it or False to filter it out
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direction
FrameDirection
default:"FrameDirection.DOWNSTREAM"
Which direction of frames to filter (DOWNSTREAM or UPSTREAM)

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Functionality

When a frame passes through the processor:
  1. System frames and end frames are always passed through
  2. Frames moving in a different direction than specified are always passed through
  3. Other frames are passed to the filter function
  4. If the filter function returns True, the frame is passed through

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Output Frames

The processor conditionally passes through frames based on:
  • Frame type (system frames and end frames always pass)
  • Frame direction (only filters in the specified direction)
  • Result of the custom filter function

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Usage Example

from pipecat.frames.frames import TextFrame, Frame
from pipecat.processors.filters import FunctionFilter
from pipecat.processors.frame_processor import FrameDirection

# Create filter that only allows TextFrames with more than 10 characters
async def long_text_filter(frame: Frame) -> bool:
    if isinstance(frame, TextFrame):
        return len(frame.text) > 10
    return False

# Apply filter to downstream frames only
text_length_filter = FunctionFilter(
    filter=long_text_filter,
    direction=FrameDirection.DOWNSTREAM
)

# Add to pipeline
pipeline = Pipeline([
    source,
    text_length_filter,  # Filters out short text frames
    destination
])

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Frame Flow

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Notes

  • Provides maximum flexibility for complex filtering logic
  • Can incorporate dynamic conditions that change at runtime
  • Only filters frames moving in the specified direction
  • Always passes through system frames for proper pipeline operation
  • Can be used to create sophisticated content-based filters
  • Supports async filter functions for complex processing