add xfyun tts service

README.md

@@ -131,6 +131,32 @@ the TTS in the pipeline. `response.text.final` fires when the turn ends,
 carrying the full concatenated assistant text and an `interrupted` flag
 (true when an `input.text` or barge-in cut the turn short).
 
+### Xfyun TTS
+
+The TTS provider can be switched to iFlytek/Xfyun's online TTS WebSocket API.
+The engine requests `aue: "raw"` PCM audio so the returned chunks can be sent
+through the existing Pipecat/product audio path without MP3 decoding.
+
+```json
+"tts": {
+  "provider": "xfyun",
+  "app_id": "your_xfyun_app_id",
+  "api_key": "your_xfyun_api_key",
+  "api_secret": "your_xfyun_api_secret",
+  "base_url": "wss://tts-api.xfyun.cn/v2/tts",
+  "voice": "x4_xiaoyan",
+  "aue": "raw",
+  "tte": "UTF8",
+  "speed": 50,
+  "volume": 50,
+  "pitch": 50,
+  "source_sample_rate_hz": 16000
+}
+```
+
+Credentials may also be provided through `XFYUN_APP_ID`, `XFYUN_API_KEY`, and
+`XFYUN_API_SECRET`.
+
 ## Stream A WAV File
 
 Start the server: