FluidInference/cv-corpus-25.0-ja

Mozilla Common Voice 25.0 - Japanese Test Set (Complete)

Dataset Description

Complete Japanese test set from Mozilla Common Voice Corpus 25.0. This dataset contains all 9,019 validated test samples, compared to the partial 2,334-sample version previously available on HuggingFace.

Key Features

• Size: 9,019 validated test utterances
• Coverage: 100% of official Common Voice 25.0 Japanese test split
• Multi-speaker: Diverse set of speakers with demographic metadata
• Quality: Community-validated recordings
• Format: MP3 audio files with full metadata
• Use case: Standard test set for Japanese ASR evaluation

Why This Dataset?

The previous HuggingFace repository (FluidInference/cv-corpus-25.0-ja) only contained 2,334 test files (26%) due to incomplete uploads. This dataset provides:

• ✅ All 9,019 test files (100%)
• ✅ Complete metadata matching official Mozilla release
• ✅ Ready-to-use format for ASR benchmarking
• ✅ No missing files or metadata mismatches

Dataset Structure

Files

cv-corpus-25.0-ja-test-only/
├── manifest.json          # Dataset manifest with split information
├── load_dataset.py        # Helper script to load all splits
├── ja_00/
│   ├── clips/             # 3,000 MP3 files
│   └── test.jsonl         # Metadata for this split
├── ja_01/
│   ├── clips/             # 3,000 MP3 files
│   └── test.jsonl         # Metadata for this split
├── ja_02/
│   ├── clips/             # 3,000 MP3 files
│   └── test.jsonl         # Metadata for this split
└── ja_03/
    ├── clips/             # 19 MP3 files
    └── test.jsonl         # Metadata for this split

Metadata Format

Each test.jsonl file contains entries like:

{
  "file_name": "common_voice_ja_12345.mp3",
  "path": "clips/common_voice_ja_12345.mp3",
  "text": "Japanese transcription text",
  "client_id": "anonymous_speaker_id",
  "up_votes": 2,
  "down_votes": 0,
  "age": "thirties",
  "gender": "male",
  "accent": "",
  "locale": "ja"
}

Note: Files are split across 4 directories (ja_00, ja_01, ja_02, ja_03) to comply with HuggingFace's 10,000 files per directory limit. Each directory contains a subset of the full test set.

Dataset Manifest

The manifest.json file provides complete information about the dataset structure:

{
  "dataset_name": "Mozilla Common Voice 25.0 - Japanese Test Set",
  "total_samples": 9019,
  "total_size_mb": 247.16,
  "num_splits": 4,
  "splits": [
    {"name": "ja_00", "num_files": 3000, ...},
    {"name": "ja_01", "num_files": 3000, ...},
    {"name": "ja_02", "num_files": 3000, ...},
    {"name": "ja_03", "num_files": 19, ...}
  ]
}

Usage

Loading with Python

import json
from pathlib import Path

def load_cv_test_set(dataset_dir="."):
    dataset_dir = Path(dataset_dir)
    samples = []

    # Load from all splits (ja_00, ja_01, ja_02, ja_03)
    for split_dir in sorted(dataset_dir.glob("ja_[0-9][0-9]")):
        metadata_file = split_dir / "test.jsonl"

        with open(metadata_file, 'r', encoding='utf-8') as f:
            for line in f:
                entry = json.loads(line)
                entry['audio_path'] = str(split_dir / entry['path'])
                samples.append(entry)

    return samples

# Load complete test set
test_samples = load_cv_test_set()
print(f"Loaded {len(test_samples)} test samples")

ASR Benchmarking

# Evaluate your ASR model
for sample in test_samples:
    audio_path = sample['audio_path']
    reference = sample['text']

    # Your ASR inference here
    hypothesis = your_asr_model(audio_path)

    # Calculate CER/WER
    cer = calculate_cer(reference, hypothesis)

Dataset Statistics

• Total samples: 9,019
• Language: Japanese (ja)
• Format: MP3 (various bitrates)
• License: CC0 1.0 (Public Domain)
• Source: Mozilla Common Voice 25.0
• Split: Test only

Comparison with Other Datasets

Dataset	Samples	Completeness
FluidInference/cv-corpus-25.0-ja	2,334	26%
This dataset	9,019	100%
Original Mozilla CV 25.0 test	9,019	100%

Citation

If you use this dataset, please cite the original Common Voice project:

@inproceedings{commonvoice:2020,
  author = {Ardila, R. and Branson, M. and Davis, K. and Henretty, M. and Kohler, M. and Meyer, J. and Morais, R. and Saunders, L. and Tyers, F. M. and Weber, G.},
  title = {Common Voice: A Massively-Multilingual Speech Corpus},
  booktitle = {Proceedings of the 12th Conference on Language Resources and Evaluation (LREC 2020)},
  pages = {4211--4215},
  year = {2020}
}

License

CC0 1.0 Universal (Public Domain)

The Common Voice dataset is released under CC0, meaning you can:

• Use for any purpose (commercial or non-commercial)
• Modify and redistribute
• No attribution required (though appreciated)

Original Source

• Project: Mozilla Common Voice
• Version: 25.0 (released 2026-03-09)
• Language: Japanese (ja)
• Original download: https://commonvoice.mozilla.org/ja/datasets

Dataset Quality

All samples in this dataset have been:

• ✅ Validated by community members
• ✅ Checked for audio quality
• ✅ Verified for transcription accuracy
• ✅ Filtered from invalidated/reported samples

Use Cases

• Japanese ASR model evaluation
• Benchmarking speech recognition systems
• Speaker diversity analysis
• Accent and demographic studies
• Standard test set for research papers

Acknowledgments

Thanks to the Mozilla Common Voice community and all the contributors who recorded and validated these audio samples.