Refactors the code based on PR comments and adds the relevant changelog entry.

CHANGELOG.md

@@ -72,6 +72,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Added `on_transcription_stopped` and `on_transcription_error` to Daily
   callbacks.
 
+- Added SSML reserved character escaping to `AzureBaseTTSService` to properly handle special characters in text sent to Azure TTS. This fixes an issue where characters like `&`, `<`, `>`, `"`, and `'` in LLM-generated text would cause TTS failures.
+- 
 ### Changed
 
 - Changed the default `url` for `NeuphonicTTSService` to

src/pipecat/services/azure/tts.py

@@ -68,6 +68,16 @@ class AzureBaseTTSService(TTSService):
     construction, voice configuration, and parameter management.
     """
 
+    # Define SSML escape mappings based on SSML reserved characters
+    # See - https://learn.microsoft.com/en-us/azure/ai-services/speech-service/speech-synthesis-markup-structure
+    SSML_ESCAPE_CHARS = {
+        "&": "&",
+        "<": "&lt;",
+        ">": "&gt;",
+        '"': "&quot;",
+        "'": "&apos;",
+    }
+
     class InputParams(BaseModel):
         """Input parameters for Azure TTS voice configuration.
 
@@ -128,14 +138,6 @@ class AzureBaseTTSService(TTSService):
             "volume": params.volume,
         }
 
-        # Define SSML escape mappings based on SSML reserved characters
-        # See - https://learn.microsoft.com/en-us/azure/ai-services/speech-service/speech-synthesis-markup-structure
-        self.ssml_escape_chars = {
-            '&': '&amp;',
-            '<': '&lt;',
-            '>': '&gt;'
-        }
-
         self._api_key = api_key
         self._region = region
         self._voice_id = voice
@@ -210,7 +212,14 @@ class AzureBaseTTSService(TTSService):
         return ssml
 
     def _escape_text(self, text: str) -> str:
-        """Escape special characters in text for SSML.
+        """Escapes XML/SSML reserved characters according to Microsoft documentation.
+
+        This method escapes the following characters:
+        - & becomes &amp;
+        - < becomes &lt;
+        - > becomes &gt;
+        - " becomes &quot;
+        - ' becomes &apos;
 
         Args:
             text: The text to escape.
@@ -219,7 +228,7 @@ class AzureBaseTTSService(TTSService):
             The escaped text.
         """
         escaped_text = text
-        for char, escape_code in self.ssml_escape_chars.items():
+        for char, escape_code in AzureBaseTTSService.SSML_ESCAPE_CHARS.items():
             escaped_text = escaped_text.replace(char, escape_code)
         return escaped_text