Add can_generate_metrics to Soniox and AWS Transcribe STT services

Commit 859cd7c9 refactored STT TTFB measurement to use the base class
start_ttfb_metrics/stop_ttfb_metrics, which are gated behind
can_generate_metrics(). Soniox and AWS Transcribe never overrode this
method (default returns False), so TTFB was silently never reported.

changelog/3813.fixed.md

@@ -0,0 +1 @@
+- Fixed STT TTFB metrics not being reported for `SonioxSTTService` and `AWSTranscribeSTTService` due to missing `can_generate_metrics()` override.

src/pipecat/services/aws/stt.py

@@ -126,6 +126,14 @@ class AWSTranscribeSTTService(WebsocketSTTService):
 
         self._receive_task = None
 
+    def can_generate_metrics(self) -> bool:
+        """Check if this service can generate processing metrics.
+
+        Returns:
+            True, as AWS Transcribe STT supports metrics generation.
+        """
+        return True
+
     def get_service_encoding(self, encoding: str) -> str:
         """Convert internal encoding format to AWS Transcribe format.
 

src/pipecat/services/soniox/stt.py

@@ -208,6 +208,14 @@ class SonioxSTTService(WebsocketSTTService):
 
         self._receive_task = None
 
+    def can_generate_metrics(self) -> bool:
+        """Check if this service can generate processing metrics.
+
+        Returns:
+            True, as Soniox STT supports metrics generation.
+        """
+        return True
+
     async def start(self, frame: StartFrame):
         """Start the Soniox STT websocket connection.