faster-whisper
Faster Whisper transcription with CTranslate2
The Lens
faster-whisper runs OpenAI's Whisper speech-to-text models up to four times faster than the original implementation while using less memory, with the same accuracy. It reimplements inference on CTranslate2, and it has quietly become the engine inside most self-hosted transcription stacks. MIT licensed, completely free.
It's a Python library, not a service: pip install, pick a model size, feed it audio. A GPU gets you faster-than-realtime transcription; CPU works fine with the small and medium models. Wrapping it in an internal API for your team is an afternoon with FastAPI, and 8GB of VRAM comfortably runs the large model in int8.
Anyone paying AssemblyAI or Deepgram per minute for plain transcription should run the math. A cheap GPU instance chews through hours of audio for pennies, and openai/whisper accuracy is the same thing you're renting. The paid APIs keep winning on streaming, speaker diarization, and zero-ops.
The catch: the models are open but the pipeline is yours. Chunking long files, retries, scaling workers, word-level timestamps, all of it. The per-minute APIs charge for exactly that boredom.
Free vs Self-Hosted vs Paid
fully freeFree Tier (Everything)
The library and every Whisper model size (tiny through large-v3), MIT licensed. Quantization (int8) for smaller memory footprints, batching, VAD filtering, word timestamps. Nothing is gated.
Self-Hosted Setup
pip install faster-whisper, models download on first run. CPU handles small/medium models for casual use; a GPU with 8GB+ VRAM runs large-v3 faster than realtime. The engineering is around the library: job queues, chunking long audio, serving it to your team. Expect a day to a working internal transcription endpoint.
Paid Tier
None. The commercial comparison is per-minute APIs: AssemblyAI around $0.12-0.37/hr of audio, Deepgram similar, OpenAI's hosted Whisper at $0.36/hr.
The Math
At 100 hours of audio a month, hosted APIs run $12-37/mo, cheap enough to not bother self-hosting. At thousands of hours, a $150-300/mo GPU instance (or spot capacity) transcribes it for a fraction of the API bill. The crossover is volume plus privacy: audio that can't leave your infrastructure makes the decision for you.
Verdict
Free and the de facto standard for self-hosted Whisper. Buy the API for streaming and diarization; run this for bulk and private transcription.
Free MIT-licensed Whisper inference. Beats per-minute APIs on cost at volume or when audio can't leave your infra.
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