mlx-whisperx 0.1.9

WhisperX-style transcription pipeline using an internal mlx-whisper ASR backend.

mlx-whisperx

mlx-whisperx is a WhisperX-style transcription pipeline for Apple Silicon. It uses a vendored mlx-whisper ASR backend, then optionally applies WhisperX forced alignment and pyannote diarization.

The project is intended to provide a practical local pipeline with WhisperX-like JSON, subtitle, and text outputs while keeping ASR execution on MLX.

Why This Project Exists

This project adds WhisperX-like functionality to an mlx-whisper workflow. The goal is to keep ASR inference on MLX for Apple Silicon while providing the pipeline pieces people commonly use from WhisperX: VAD chunking, forced alignment, word timestamps, diarization hooks, and familiar JSON/subtitle outputs.

The implementation borrows ideas and code from both upstream projects:

• WhisperX, for the pipeline structure, alignment workflow, diarization integration, and output conventions.
• mlx-whisper, for the Apple Silicon ASR backend and model execution path.

This repository vendors and adapts code where needed so the pieces work together as a standalone mlx-whisperx package.

Pipeline

audio -> VAD -> mlx-whisper ASR -> forced alignment -> optional diarization -> writers

Default behavior:

• ASR model: mlx-community/whisper-large-v3-mlx
• VAD backend: pyannote when available, otherwise Silero
• Chunking: VAD chunks decoded in batches of 8 (--batch_size 8)
• Decoding: beam search with beam_size=5 and temperature=0
• Alignment: enabled for transcription
• Diarization: disabled unless --diarize is passed

Installation

Clone the repository and install it into a Python environment:

git clone https://github.com/seedds/mlx-whisperx.git
cd mlx-whisperx
python -m pip install -e .

The published package constrains the alignment stack to a tested range:

• torch 2.11.x
• torchaudio 2.11.x
• transformers >=5,<6

torchvision is not required for alignment.

Install diarization support when you want pyannote VAD and diarization instead of the automatic Silero fallback:

python -m pip install -e ".[diarize]"

Install everything this repository currently exposes:

python -m pip install -e ".[full]"

ffmpeg must be available on PATH because audio loading is handled through the ffmpeg CLI.

On macOS with Homebrew:

brew install ffmpeg

Pyannote VAD and diarization use pyannote models and may require a Hugging Face token, depending on the selected model.

Usage

mlx-whisperx AUDIO [AUDIO ...] [OPTIONS]

By default, mlx-whisperx:

• uses mlx-community/whisper-large-v3-mlx
• runs Silero VAD by default
• performs forced alignment for word timestamps
• writes outputs to the current directory
• writes every supported output format when --output_format is not specified

Common options:

• --model: local model path or Hugging Face repo
• --language: language code such as en, ja, or fr
• --task: transcribe or translate
• --output_dir: directory to write output files
• --output_name: custom basename for output files
• --output_format: all, json, srt, vtt, txt, tsv, or aud
• --no_align: skip forced alignment
• --diarize: attach speaker labels when diarization is enabled
• --hf_token: Hugging Face token for gated pyannote models

Example: output JSON

mlx-whisperx audio.wav \
  --output_dir transcripts \
  --output_name audio \
  --output_format json

This writes transcripts/audio.json.

Example JSON output:

{
  "segments": [
    {
      "start": 0.0,
      "end": 2.52,
      "text": "Hello and welcome to mlx-whisperx.",
      "words": [
        {"word": "Hello", "start": 0.0, "end": 0.42, "score": 0.99},
        {"word": "and", "start": 0.44, "end": 0.58, "score": 0.98},
        {"word": "welcome", "start": 0.6, "end": 1.05, "score": 0.97},
        {"word": "to", "start": 1.07, "end": 1.18, "score": 0.98},
        {"word": "mlx-whisperx.", "start": 1.2, "end": 2.52, "score": 0.96}
      ]
    }
  ],
  "word_segments": [
    {"word": "Hello", "start": 0.0, "end": 0.42, "score": 0.99},
    {"word": "and", "start": 0.44, "end": 0.58, "score": 0.98}
  ],
  "language": "en"
}

Example: output SRT

mlx-whisperx audio.wav \
  --output_dir subtitles \
  --output_name audio \
  --output_format srt \
  --max_line_width 42 \
  --max_line_count 2

This writes subtitles/audio.srt.

Example SRT output:

1
00:00:00,000 --> 00:00:02,520
Hello and welcome to
mlx-whisperx.

2
00:00:02,700 --> 00:00:05,100
This example shows subtitle
output.

Complete example with optional parameters:

mlx-whisperx audio.wav \
  --model mlx-community/whisper-large-v3-mlx \
  --model_dir ./models \
  --model_cache_only False \
  --device cpu \
  --compute_type float32 \
  --output_dir ./out \
  --output_name meeting \
  --output_format all \
  --verbose True \
  --log-level info \
  --task transcribe \
  --language en \
  --align_model jonatasgrosman/wav2vec2-large-xlsr-53-english \
  --interpolate_method nearest \
  --return_char_alignments \
  --vad_method pyannote \
  --vad_onset 0.5 \
  --vad_offset 0.363 \
  --vad_model pyannote/segmentation-3.0 \
  --chunk_size 30 \
  --vad_dump_path ./out/meeting.vad.json \
  --diarize \
  --min_speakers 2 \
  --max_speakers 4 \
  --diarize_model pyannote/speaker-diarization-community-1 \
  --speaker_embeddings \
  --hf_token YOUR_HF_TOKEN \
  --temperature 0.0 \
  --temperature_increment_on_fallback 0.2 \
  --best_of 5 \
  --beam_size 5 \
  --patience 1.0 \
  --length_penalty 1.0 \
  --suppress_tokens -1 \
  --suppress_numerals \
  --initial_prompt "Technical meeting about MLX WhisperX." \
  --hotwords "MLX, WhisperX, pyannote, diarization" \
  --condition_on_previous_text True \
  --compression_ratio_threshold 2.4 \
  --logprob_threshold -1.0 \
  --no_speech_threshold 0.6 \
  --max_line_width 42 \
  --max_line_count 2 \
  --max_words_per_line 8 \
  --highlight_words False \
  --print_progress True

Notes:

• --output_format all writes .txt, .vtt, .srt, .tsv, .json, and .aud.
• --max_line_count only has an effect when --max_line_width is also set.
• --highlight_words applies to srt and vtt.
• --hf_token is only needed for gated pyannote models.

Python API

from mlx_whisperx import transcribe

result = transcribe(
    "audio.wav",
    model="mlx-community/whisper-large-v3-mlx",
    language="en",
)

Print one transcript segment per line:

for segment in result["segments"]:
    print(segment["text"].strip())

Print segment timestamps:

for segment in result["segments"]:
    print(f"[{segment['start']:.2f} -> {segment['end']:.2f}] {segment['text'].strip()}")

Print word-level timestamps:

for word in result["word_segments"]:
    print(f"[{word['start']:.2f} -> {word['end']:.2f}] {word['word']}")

Common API options match the CLI names:

result = transcribe(
    "audio.wav",
    model="mlx-community/whisper-large-v3-mlx",
    language="en",
    beam_size=5,
    temperature=0.0,
    no_align=False,
    diarize=False,
)

language accepts either canonical codes such as en or case-insensitive names and aliases such as English or Portuguese.

Output Schema

JSON output follows the WhisperX-style shape:

{
  "segments": [
    {
      "start": 0.0,
      "end": 2.5,
      "text": "Example transcript text.",
      "words": [
        {"word": "Example", "start": 0.0, "end": 0.6, "score": 0.98}
      ]
    }
  ],
  "word_segments": [
    {"word": "Example", "start": 0.0, "end": 0.6, "score": 0.98}
  ],
  "language": "en"
}

When diarization is enabled, speaker labels are included where available:

{"word": "Hello", "start": 0.0, "end": 0.4, "score": 0.99, "speaker": "SPEAKER_00"}

CLI Reference

Basic options:

• --model: mlx-whisper model directory or Hugging Face repo.
• --language: language code or case-insensitive name/alias. If omitted, language is auto-detected by ASR.
• --task: transcribe or translate.
• --output_format: all, srt, vtt, txt, tsv, json, or aud.
• --output_dir: directory for output files.
• --output_name: custom output basename.
• --verbose: print transcript and logs.

English-only Whisper models such as .en checkpoints force language=en and do not support --task translate.

Decoding options:

• --temperature: sampling temperature. Default is 0.0.
• --beam_size: beam size when temperature=0. Default is 5.
• --best_of: number of candidates when sampling with temperature > 0.
• --patience: beam-search patience.
• --length_penalty: beam-search length penalty.
• --suppress_tokens: comma-separated token IDs to suppress.
• --suppress_numerals: suppress numeric and currency-symbol tokens.
• --initial_prompt: initial prompt for ASR.
• --hotwords: hint phrases appended to the prompt.
• --condition_on_previous_text: prompt backend windows with previous text inside each VAD chunk.

Precision and model-cache options:

• --compute_type float16: force MLX ASR fp16. This is the default.
• --compute_type float32: force MLX ASR fp32.
• --model_dir: cache directory for ASR, alignment, pyannote VAD, and diarization models.
• --model_cache_only: cached ASR, alignment, pyannote VAD, and diarization models only.

VAD options:

• --vad_method silero: default VAD mode.
• --vad_method auto: prefer pyannote and fall back to Silero if pyannote cannot initialize.
• --vad_method pyannote: require pyannote VAD and do not fall back.
• --vad_method silero: use Silero VAD directly.
• --vad_onset: VAD onset threshold.
• --vad_offset: VAD offset threshold.
• --vad_model: Hugging Face pyannote segmentation model used with --vad_method pyannote. Defaults to pyannote/segmentation-3.0.
• --chunk_size: merged VAD chunk size in seconds.
• --no_vad: transcribe the full file as one chunk.
• --clip_timestamps: comma-separated clip start/end pairs in seconds. Requires --no_vad.
• --vad_dump_path: write VAD chunks and settings to JSON.

Batching options:

• --batch_size: number of chunks decoded together in one pass. Defaults to 8. Higher values are faster but use more memory; 1 disables batching. Batching is skipped automatically when --condition_on_previous_text is set.

When using the default --vad_method silero, or when the --vad_method auto path falls back to Silero, Silero loads from the local Torch Hub cache first. To force a local Silero checkout, set:

export MLX_WHISPERX_SILERO_VAD_PATH=/path/to/snakers4_silero-vad

Alignment options:

• --no_align: skip forced alignment.
• --allow_missing_alignment_deps: continue without forced alignment when alignment dependencies are unavailable.
• --align_model: override the alignment model.
• --interpolate_method: nearest, linear, or ignore.
• --return_char_alignments: include character alignments in JSON.

Diarization options:

• --diarize: assign speaker labels.
• --diarize_model: pyannote diarization model name.
• --min_speakers: minimum speaker count.
• --max_speakers: maximum speaker count.
• --speaker_embeddings: include speaker embeddings in JSON when available.
• --hf_token: Hugging Face token for gated pyannote models.

Subtitle options:

• --max_line_width: target subtitle line width.
• --max_line_count: maximum lines per subtitle cue. Requires --max_line_width.
• --max_words_per_line: maximum words per subtitle cue.
• --highlight_words: underline the active word in SRT/VTT output.

Examples

Inspect VAD chunks before ASR:

mlx-whisperx audio.wav \
  --output_format json \
  --vad_dump_path audio.vad.json

Transcribe only selected clips without VAD chunking:

mlx-whisperx audio.wav \
  --no_vad \
  --clip_timestamps 0,15,30,45 \
  --output_format json

Run deterministic beam search explicitly:

mlx-whisperx audio.wav \
  --language en \
  --temperature 0 \
  --beam_size 5 \
  --output_format json

Use temperature fallback:

mlx-whisperx audio.wav \
  --temperature 0 \
  --temperature_increment_on_fallback 0.2

Suppress numerals and currency symbols during decoding:

mlx-whisperx audio.wav --suppress_numerals --output_format json

Require pyannote VAD instead of the default Silero behavior:

mlx-whisperx audio.wav \
  --vad_method pyannote \
  --vad_model pyannote/segmentation-3.0 \
  --hf_token YOUR_HF_TOKEN \
  --output_format json

Skip forced alignment:

mlx-whisperx audio.wav --no_align --output_format json

Continue when alignment dependencies are unavailable:

mlx-whisperx audio.wav --allow_missing_alignment_deps --output_format json

Run diarization:

mlx-whisperx audio.wav \
  --diarize \
  --hf_token YOUR_HF_TOKEN \
  --output_format json

Process multiple files:

mlx-whisperx first.wav second.wav third.wav --output_dir transcripts --output_format all

Current Behavior and Limitations

• ASR decodes merged VAD chunks in batches of --batch_size (default 8); set --batch_size 1 to decode serially.
• Batching is disabled automatically when --condition_on_previous_text is set, because chunks then depend on each other.
• translate skips forced alignment because alignment models are transcription-language specific.
• Missing torch, torchaudio, or transformers still fail alignment by default; pass --allow_missing_alignment_deps to continue with ASR-only output instead.
• clip_timestamps is only supported with --no_vad because VAD chunking changes the timing base before ASR runs.
• Pyannote VAD and diarization depend on a compatible PyTorch, torchaudio, pyannote installation, and Hugging Face model access when the selected model is gated. Without that stack, use the default --vad_method silero path or let --vad_method auto fall back to Silero VAD.
• The vendored ASR backend lives under mlx_whisperx.backend.mlx_whisper so decoder behavior can be changed without modifying external reference repositories.

Development Checks

Compile the package:

python -m py_compile mlx_whisperx/**/*.py

Check CLI help:

python -m mlx_whisperx --help

Build a wheel:

python -m build