When to Use
- Transcribing recordings or files — Use batch ASR (this page). 210x real-time, 2.5% WER on English.
- Live captions while user speaks — Use Streaming ASR with Parakeet EOU.
- Domain-specific terms keep getting wrong — Add Custom Vocabulary boosting (91.7% F-score on earnings calls).
Models
| Model | Languages | Audio Length | Use Case |
|---|
| Parakeet TDT v3 | 25 European | ~15s chunks | Default — multilingual |
| Parakeet TDT v2 | English only | ~15s chunks | Best English accuracy |
| Parakeet EOU | English | 320ms chunks | Real-time streaming |
Batch Transcription
Real-time factor: ~120x on M4 Pro (1 minute of audio in ~0.5 seconds).
import FluidAudio
Task {
let models = try await AsrModels.downloadAndLoad(version: .v3) // .v2 for English-only
let asrManager = AsrManager(config: .default)
try await asrManager.initialize(models: models)
let samples = try AudioConverter().resampleAudioFile(
path: "path/to/audio.wav"
)
let result = try await asrManager.transcribe(samples, source: .system)
print("Transcription: \(result.text)")
print("Confidence: \(result.confidence)")
}
Transcribing from a File URL
let audioURL = URL(fileURLWithPath: "/path/to/audio.wav")
let result = try await asrManager.transcribe(audioURL, source: .system)
print(result.text)
Do not parse WAV/PCM bytes by hand. Always convert with AudioConverter so differing bit depths, channel layouts, metadata chunks, or compressed formats get normalized to the 16 kHz mono Float32 tensors that Parakeet expects.
Choosing a Model Version
- v2 — English only. Tighter vocabulary, better recall on long-form English audio.
- v3 — 25 European languages. English accuracy is still strong, but the broader vocab slightly trails v2 on rare words.
Both share the same API surface—set AsrModelVersion in code or pass --model-version in the CLI.
let models = try await AsrModels.downloadAndLoad(version: .v2)
Benchmarks
LibriSpeech test-clean (2,620 files, 5.4h audio):
| Model | WER | RTFx |
|---|
| Parakeet TDT v3 | 2.5% | 156x |
| Parakeet TDT v2 | 2.1% | 146x |
| Parakeet EOU (320ms) | 4.9% | 12x |
| Model | Avg WER | RTFx |
|---|
| Parakeet TDT v3 | 14.7% | 210x |
CLI
# Transcribe (multilingual)
swift run fluidaudio transcribe audio.wav
# English-only (better recall)
swift run fluidaudio transcribe audio.wav --model-version v2
# Multiple files in parallel
swift run fluidaudio multi-stream audio1.wav audio2.wav
# Benchmark on LibriSpeech
swift run fluidaudio asr-benchmark --subset test-clean --max-files 50
