Filter

Drops messages that fail a {{type:Bool}} predicate. Pairs a value stream with a boolean stream that ticks alongside it.

How it fits

{{type:t}}     -+
                +-> {{component:filter}} -> {{type:t}} (only when the predicate tick was true)
{{type:Bool}}  -+

Typical backends

• Sharp-only OCR: {{component:input_camera}} paired with {{component:measure_image_sharpness_opencv}} -> {{component:filter}} -> {{component:extract_text_paddleocr}}.
• Threshold gate: numeric stream + {{component:evaluate_expression}} (threshold compare) -> {{component:filter}} -> downstream.
• VAD-gated transcription: audio + {{component:detect_voice_activity_silero_vad}} -> {{component:filter}} -> {{component:transcribe_audio_faster_whisper}}.
• Class-of-interest gate: detections + {{component:evaluate_expression}} (label match) -> {{component:filter}} -> {{component:output_json_http}}.

Caveats

• The value and predicate streams must tick together; mis-aligned cadences desync the gate.
• Output cadence is irregular — ticks where the predicate was false produce nothing, which can starve downstream rate assumptions.
• Predicate evaluation is per-tick and stateless; sliding-window logic belongs upstream.