[Model] Add IndexTTS2 text-to-speech support (#3838)

Signed-off-by: BeatSeat <wendavid552@gmail.com>
Signed-off-by: David <david@podcast.ai>
Signed-off-by: wendavid552 <wendavid552@gmail.com>
Signed-off-by: WenDavid <davidzhangcf@foxmail.com>

vllm_omni/model_executor/models/indextts2/prompt_utils.py

@@ -0,0 +1,47 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""Prompt helpers for IndexTTS2 talker prefill."""
+
+from __future__ import annotations
+
+from functools import lru_cache
+
+from vllm_omni.model_executor.models.indextts2.preprocess_utils import resolve_model_file
+from vllm_omni.model_executor.models.indextts2.tokenizer import IndexTTS2Tokenizer
+
+_CONDITIONING_PREFIX_TOKENS = 34
+_TEXT_WRAPPER_TOKENS = 2
+_START_MEL_TOKENS = 1
+
+
+def _resolve_bpe_model_path(model_id_or_path: str) -> str:
+    path = resolve_model_file(model_id_or_path, "bpe.model")
+    if path is None:
+        raise FileNotFoundError(f"Could not resolve bpe.model for {model_id_or_path!r}")
+    return path
+
+
+@lru_cache(maxsize=16)
+def _get_text_tokenizer(model_id_or_path: str) -> IndexTTS2Tokenizer:
+    return IndexTTS2Tokenizer(_resolve_bpe_model_path(model_id_or_path), model_dir=model_id_or_path)
+
+
+def estimate_indextts2_prefill_prompt_len(model_id_or_path: str, text: str) -> int:
+    """Return the placeholder prompt length expected by the IndexTTS2 talker.
+
+    The model-side prefill replaces placeholder embeddings with:
+    34 conditioning tokens, text tokens wrapped with start/stop markers, and
+    one start-mel token.
+    """
+    tokenizer = _get_text_tokenizer(model_id_or_path)
+    text_token_count = len(tokenizer.encode(text, add_special_tokens=False)) + _TEXT_WRAPPER_TOKENS
+    return _CONDITIONING_PREFIX_TOKENS + text_token_count + _START_MEL_TOKENS
+
+
+def build_indextts2_prefill_prompt_ids(
+    model_id_or_path: str,
+    text: str,
+    *,
+    placeholder_token_id: int = 1,
+) -> list[int]:
+    return [placeholder_token_id] * estimate_indextts2_prefill_prompt_len(model_id_or_path, text)