Whisper - Robust Speech Recognition

OpenAI's multilingual speech recognition model.

When to use Whisper

Use when:

• Speech-to-text transcription (99 languages)

• Podcast/video transcription

• Meeting notes automation

• Translation to English

• Noisy audio transcription

• Multilingual audio processing

Metrics:

• 72,900+ GitHub stars

• 99 languages supported

• Trained on 680,000 hours of audio

• MIT License

Use alternatives instead:

• AssemblyAI: Managed API, speaker diarization

• Deepgram: Real-time streaming ASR

• Google Speech-to-Text: Cloud-based

Quick start

Installation

Requires Python 3.8-3.11

pip install -U openai-whisper

Requires ffmpeg

macOS: brew install ffmpeg

Ubuntu: sudo apt install ffmpeg

Windows: choco install ffmpeg

Basic transcription

import whisper

Load model

model = whisper.load_model("base")

Transcribe

result = model.transcribe("audio.mp3")

Print text

print(result["text"])

Access segments

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

Model sizes

Available models

models = ["tiny", "base", "small", "medium", "large", "turbo"]

Load specific model

model = whisper.load_model("turbo") # Fastest, good quality

Model Parameters English-only Multilingual Speed VRAM

tiny 39M ✓ ✓ ~32x ~1 GB

base 74M ✓ ✓ ~16x ~1 GB

small 244M ✓ ✓ ~6x ~2 GB

medium 769M ✓ ✓ ~2x ~5 GB

large 1550M ✗ ✓ 1x ~10 GB

turbo 809M ✗ ✓ ~8x ~6 GB

Recommendation: Use turbo for best speed/quality, base for prototyping

Transcription options

Language specification

Auto-detect language

result = model.transcribe("audio.mp3")

Specify language (faster)

result = model.transcribe("audio.mp3", language="en")

Supported: en, es, fr, de, it, pt, ru, ja, ko, zh, and 89 more

Task selection

Transcription (default)

result = model.transcribe("audio.mp3", task="transcribe")

Translation to English

result = model.transcribe("spanish.mp3", task="translate")

Input: Spanish audio → Output: English text

Initial prompt

Improve accuracy with context

result = model.transcribe( "audio.mp3", initial_prompt="This is a technical podcast about machine learning and AI." )

Helps with:

- Technical terms

- Proper nouns

- Domain-specific vocabulary

Timestamps

Word-level timestamps

result = model.transcribe("audio.mp3", word_timestamps=True)

for segment in result["segments"]: for word in segment["words"]: print(f"{word['word']} ({word['start']:.2f}s - {word['end']:.2f}s)")

Temperature fallback

Retry with different temperatures if confidence low

result = model.transcribe( "audio.mp3", temperature=(0.0, 0.2, 0.4, 0.6, 0.8, 1.0) )

Command line usage

Basic transcription

whisper audio.mp3

Specify model

whisper audio.mp3 --model turbo

Output formats

whisper audio.mp3 --output_format txt # Plain text whisper audio.mp3 --output_format srt # Subtitles whisper audio.mp3 --output_format vtt # WebVTT whisper audio.mp3 --output_format json # JSON with timestamps

Language

whisper audio.mp3 --language Spanish

Translation

whisper spanish.mp3 --task translate

Batch processing

import os

audio_files = ["file1.mp3", "file2.mp3", "file3.mp3"]

for audio_file in audio_files: print(f"Transcribing {audio_file}...") result = model.transcribe(audio_file)

# Save to file
output_file = audio_file.replace(".mp3", ".txt")
with open(output_file, "w") as f:
    f.write(result["text"])

Real-time transcription

For streaming audio, use faster-whisper

pip install faster-whisper

from faster_whisper import WhisperModel

model = WhisperModel("base", device="cuda", compute_type="float16")

Transcribe with streaming

segments, info = model.transcribe("audio.mp3", beam_size=5)

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

GPU acceleration

import whisper

Automatically uses GPU if available

model = whisper.load_model("turbo")

Force CPU

model = whisper.load_model("turbo", device="cpu")

Force GPU

model = whisper.load_model("turbo", device="cuda")

10-20× faster on GPU

Integration with other tools

Subtitle generation

Generate SRT subtitles

whisper video.mp4 --output_format srt --language English

Output: video.srt

With LangChain

from langchain.document_loaders import WhisperTranscriptionLoader

loader = WhisperTranscriptionLoader(file_path="audio.mp3") docs = loader.load()

Use transcription in RAG

from langchain_chroma import Chroma from langchain_openai import OpenAIEmbeddings

vectorstore = Chroma.from_documents(docs, OpenAIEmbeddings())

Extract audio from video

Use ffmpeg to extract audio

ffmpeg -i video.mp4 -vn -acodec pcm_s16le audio.wav

Then transcribe

whisper audio.wav

Best practices

• Use turbo model - Best speed/quality for English

• Specify language - Faster than auto-detect

• Add initial prompt - Improves technical terms

• Use GPU - 10-20× faster

• Batch process - More efficient

• Convert to WAV - Better compatibility

• Split long audio - <30 min chunks

• Check language support - Quality varies by language

• Use faster-whisper - 4× faster than openai-whisper

• Monitor VRAM - Scale model size to hardware

Performance

Model Real-time factor (CPU) Real-time factor (GPU)

tiny ~0.32 ~0.01

base ~0.16 ~0.01

turbo ~0.08 ~0.01

large ~1.0 ~0.05

Real-time factor: 0.1 = 10× faster than real-time

Language support

Top-supported languages:

• English (en)

• Spanish (es)

• French (fr)

• German (de)

• Italian (it)

• Portuguese (pt)

• Russian (ru)

• Japanese (ja)

• Korean (ko)

• Chinese (zh)

Full list: 99 languages total

Limitations

• Hallucinations - May repeat or invent text

• Long-form accuracy - Degrades on >30 min audio

• Speaker identification - No diarization

• Accents - Quality varies

• Background noise - Can affect accuracy

• Real-time latency - Not suitable for live captioning

Resources

• GitHub: https://github.com/openai/whisper ⭐ 72,900+

• Paper: https://arxiv.org/abs/2212.04356

• Model Card: https://github.com/openai/whisper/blob/main/model-card.md

• Colab: Available in repo

• License: MIT