processors(filters): add IdentityFilter

CHANGELOG.md

@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- Added `IdentityFilter`. This is the simplest frame filter that lets through
+  all incoming frames.
+
 - New `STTMuteStrategy` called `FUNCTION_CALL` which mutes the STT service
   during LLM function calls.
 

src/pipecat/processors/filters/identity_filter.py

@@ -0,0 +1,30 @@
+#
+# Copyright (c) 2024, Daily
+#
+# SPDX-License-Identifier: BSD 2-Clause License
+#
+
+from pipecat.frames.frames import Frame
+from pipecat.processors.frame_processor import FrameDirection, FrameProcessor
+
+
+class IdentityFilter(FrameProcessor):
+    """A pass-through filter that forwards all frames without modification.
+
+    This filter acts as a transparent passthrough, allowing all frames to flow
+    through unchanged. It can be useful when testing `ParallelPipeline` to
+    create pipelines that pass through frames (no frames should be repeated).
+
+    """
+
+    def __init__(self, **kwargs):
+        super().__init__(**kwargs)
+
+    #
+    # Frame processor
+    #
+
+    async def process_frame(self, frame: Frame, direction: FrameDirection):
+        """Process an incoming frame by passing it through unchanged."""
+        await super().process_frame(frame, direction)
+        await self.push_frame(frame, direction)