[Frontend] Add configurable output sample rate to Speech API (#6553)

Signed-off-by: 郑倩倩 <2458983186@qq.com>
Co-authored-by: Hongsheng Liu <liuhongsheng4@huawei.com>

examples/online_serving/text_to_speech/qwen3_tts/openai_speech_client.py

@@ -1,3 +1,6 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM-Omni project
+
 """OpenAI-compatible client for Qwen3-TTS via /v1/audio/speech endpoint.
 
 This script demonstrates how to use the OpenAI-compatible speech API
@@ -74,6 +77,8 @@ def run_tts_generation(args) -> None:
         "voice": args.speaker,
         "response_format": args.response_format,
     }
+    if args.sample_rate is not None:
+        payload["sample_rate"] = args.sample_rate
 
     # Add optional parameters
     if args.instructions:
@@ -246,6 +251,13 @@ def parse_args():
         choices=["wav", "mp3", "flac", "pcm", "aac", "opus"],
         help="Audio output format (default: wav)",
     )
+    parser.add_argument(
+        "--sample-rate",
+        type=int,
+        default=None,
+        choices=[8000, 24000],
+        help="Output sample rate in Hz (default: model native)",
+    )
     parser.add_argument(
         "--output",
         "-o",