From 952319de90714170ac87fad6dcf620ff6f1b6eb5 Mon Sep 17 00:00:00 2001
From: Laurent Mazare <laurent.mazare@gmail.com>
Date: Tue, 8 Jul 2025 16:04:50 +0200
Subject: [PATCH] Add a MLX STT example that uses VAD. (#70)

* Add a MLX STT example that uses VAD.

* VAD support.

* More MLX VAD example.

* Use the latest moshi-mlx.
---
 scripts/stt_from_file_mlx.py | 95 ++++++++++++++++++++++++++++++++++++
 1 file changed, 95 insertions(+)
 create mode 100644 scripts/stt_from_file_mlx.py

diff --git a/scripts/stt_from_file_mlx.py b/scripts/stt_from_file_mlx.py
new file mode 100644
index 0000000..f255b7a
--- /dev/null
+++ b/scripts/stt_from_file_mlx.py
@@ -0,0 +1,95 @@
+# /// script
+# requires-python = ">=3.12"
+# dependencies = [
+#     "huggingface_hub",
+#     "moshi_mlx==0.2.10",
+#     "numpy",
+#     "sentencepiece",
+#     "sounddevice",
+#     "sphn",
+# ]
+# ///
+
+import argparse
+import json
+
+import mlx.core as mx
+import mlx.nn as nn
+import sentencepiece
+import sphn
+from huggingface_hub import hf_hub_download
+from moshi_mlx import models, utils
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser()
+    parser.add_argument("in_file", help="The file to transcribe.")
+    parser.add_argument("--max-steps", default=4096)
+    parser.add_argument("--hf-repo", default="kyutai/stt-1b-en_fr-mlx")
+    parser.add_argument(
+        "--vad", action="store_true", help="Enable VAD (Voice Activity Detection)."
+    )
+    args = parser.parse_args()
+
+    audio, _ = sphn.read(args.in_file, sample_rate=24000)
+    lm_config = hf_hub_download(args.hf_repo, "config.json")
+    with open(lm_config, "r") as fobj:
+        lm_config = json.load(fobj)
+    mimi_weights = hf_hub_download(args.hf_repo, lm_config["mimi_name"])
+    moshi_name = lm_config.get("moshi_name", "model.safetensors")
+    moshi_weights = hf_hub_download(args.hf_repo, moshi_name)
+    text_tokenizer = hf_hub_download(args.hf_repo, lm_config["tokenizer_name"])
+
+    lm_config = models.LmConfig.from_config_dict(lm_config)
+    model = models.Lm(lm_config)
+    model.set_dtype(mx.bfloat16)
+    if moshi_weights.endswith(".q4.safetensors"):
+        nn.quantize(model, bits=4, group_size=32)
+    elif moshi_weights.endswith(".q8.safetensors"):
+        nn.quantize(model, bits=8, group_size=64)
+
+    print(f"loading model weights from {moshi_weights}")
+    if args.hf_repo.endswith("-candle"):
+        model.load_pytorch_weights(moshi_weights, lm_config, strict=True)
+    else:
+        model.load_weights(moshi_weights, strict=True)
+
+    print(f"loading the text tokenizer from {text_tokenizer}")
+    text_tokenizer = sentencepiece.SentencePieceProcessor(text_tokenizer)  # type: ignore
+
+    print(f"loading the audio tokenizer {mimi_weights}")
+    audio_tokenizer = models.mimi.Mimi(models.mimi_202407(32))
+    audio_tokenizer.load_pytorch_weights(str(mimi_weights), strict=True)
+    print("warming up the model")
+    model.warmup()
+    gen = models.LmGen(
+        model=model,
+        max_steps=args.max_steps,
+        text_sampler=utils.Sampler(top_k=25, temp=0),
+        audio_sampler=utils.Sampler(top_k=250, temp=0.8),
+        check=False,
+    )
+
+    print(f"starting inference {audio.shape}")
+    audio = mx.concat([mx.array(audio), mx.zeros((1, 48000))], axis=-1)
+    last_print_was_vad = False
+    for start_idx in range(0, audio.shape[-1] // 1920 * 1920, 1920):
+        block = audio[:, None, start_idx : start_idx + 1920]
+        other_audio_tokens = audio_tokenizer.encode_step(block).transpose(0, 2, 1)
+        if args.vad:
+            text_token, vad_heads = gen.step_with_extra_heads(other_audio_tokens[0])
+            if vad_heads:
+                pr_vad = vad_heads[2][0, 0, 0].item()
+                if pr_vad > 0.5 and not last_print_was_vad:
+                    print(" [end of turn detected]")
+                    last_print_was_vad = True
+        else:
+            text_token = gen.step(other_audio_tokens[0])
+        text_token = text_token[0].item()
+        audio_tokens = gen.last_audio_tokens()
+        _text = None
+        if text_token not in (0, 3):
+            _text = text_tokenizer.id_to_piece(text_token)  # type: ignore
+            _text = _text.replace("▁", " ")
+            print(_text, end="", flush=True)
+            last_print_was_vad = False
+    print()