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fix: use EXTERNAL turn detection for Speechmatics in LiveKit pipeline 

ADAPTIVE mode enables a second client-side Silero VAD inside the
Speechmatics SDK that conflicts with LiveKit's own VAD pipeline,
causing no transcription to be returned. EXTERNAL mode delegates
turn detection to LiveKit.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
hailin 2026-03-03 01:31:33 -08:00
parent 9daf0e3b4f
commit db4e70e30c
1 changed files with 8 additions and 4 deletions
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12
packages/services/voice-agent/src/plugins/speechmatics_stt.py
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@ -9,7 +9,7 @@ by the livekit-plugins-speechmatics package.
""" """
import logging import logging
from livekit.plugins import speechmatics from livekit.plugins.speechmatics import STT, TurnDetectionMode
logger = logging.getLogger(__name__) logger = logging.getLogger(__name__)
@ -25,7 +25,7 @@ _LANG_MAP = {
} }
def create_speechmatics_stt(language: str = "cmn") -> speechmatics.STT: def create_speechmatics_stt(language: str = "cmn") -> STT:
"""Create a Speechmatics STT instance for the voice pipeline. """Create a Speechmatics STT instance for the voice pipeline.
Args: Args:
@ -36,13 +36,17 @@ def create_speechmatics_stt(language: str = "cmn") -> speechmatics.STT:
Configured speechmatics.STT instance. Configured speechmatics.STT instance.
""" """
sm_lang = _LANG_MAP.get(language, language) sm_lang = _LANG_MAP.get(language, language)
stt = speechmatics.STT( stt = STT(
language=sm_lang, language=sm_lang,
include_partials=True, include_partials=True,
# Use EXTERNAL turn detection so LiveKit's own VAD handles turn
# boundaries. ADAPTIVE enables a second client-side Silero VAD inside
# the Speechmatics SDK which conflicts with LiveKit's pipeline.
turn_detection_mode=TurnDetectionMode.EXTERNAL,
) )
# Workaround: LiveKit's LanguageCode normalizes ISO 639-3 "cmn" back to # Workaround: LiveKit's LanguageCode normalizes ISO 639-3 "cmn" back to
# ISO 639-1 "zh", but Speechmatics expects "cmn". Override the internal # ISO 639-1 "zh", but Speechmatics expects "cmn". Override the internal
# option after construction so the raw Speechmatics code is sent. # option after construction so the raw Speechmatics code is sent.
stt._stt_options.language = sm_lang # type: ignore[assignment] stt._stt_options.language = sm_lang # type: ignore[assignment]
logger.info("Speechmatics STT created: language=%s (input=%s)", sm_lang, language) logger.info("Speechmatics STT created: language=%s (input=%s), turn_detection=EXTERNAL", sm_lang, language)
return stt return stt