ExpressionDelivery (expressive/expression.py)

Copyright (c) 2024-2026, Daily SPDX-License-Identifier: BSD 2-Clause License

# Source: https://github.com/dograh-hq/pipecat | License: BSD-2-Clause | Copyright 2024–2026, Daily
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# Copyright (c) 2024-2026, Daily
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# SPDX-License-Identifier: BSD 2-Clause License
#

"""Expression capabilities: what a TTS service can perform.

Part of expressive conversation, which lets an agent hear how something was
said and answer in kind. An LLM writes expression into its reply as inline
tags: ``[[name]]`` for a sound or silence at one point, ``<<name>>`` for the
delivery of the words after it, ``<<name: words>>`` for the delivery of just
those words, and ``^^word^^`` to stress a word. A delivery lasts until the next
delivery tag or the end of the response, and ``<<neutral>>`` returns to the
voice's baseline.

For exa

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