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How to Build a Real-Time Phone Call Transcription Pipeline with Telnyx and OpenAI Whisper (self.Telnyx)<br>submitted 5 hours ago by General_Piglet_8242

What this example does

This example wires up the smallest useful phone-call-to-AI-response pipeline:

An outbound call goes out via Telnyx Call Control

Telnyx records the call audio and saves it to a hosted URL

A call.recording.saved webhook fires

The app downloads the audio, transcribes it with OpenAI Whisper, generates a contextual response with GPT-4, and plays it back through Telnyx TTS

It's about 245 lines of Python , end-to-end. It's a demo , not production code — the post will walk through which specific lines need hardening before this runs at any real volume.

The full code lives in telnyx-code-examples/call-whisper-monitoring-python. This is an Infrastructure  pillar example — it demonstrates the agent-platform thesis by chaining Telnyx call control with OpenAI inference behind a single webhook, instead of stitching together four separate vendors.

Why pair Telnyx Call Recording with OpenAI Whisper?

Telnyx Call Control records the call audio to a hosted URL (when recording is enabled on the Call Control Application in the Portal). OpenAI Whisper turns that audio into text in a single API call. Pairing them gives you a phone-call-to-transcript pipeline in three webhook calls, no media servers, no S3 buckets, no transcription worker pool.

The catch: Telnyx owns the recording pipeline (capture, storage, webhook delivery); OpenAI owns the inference (Whisper + GPT-4 + future models). You own the glue — the webhook handler, the retry policy, the timing budget, and the state management.

Most "build a phone call AI" tutorials skip that glue. This one doesn't.

The Four-Stage Pipeline

POST /calls/initiate<br>┌──────────────────────┐<br>│ Telnyx Voice API │ ──► outbound call rings<br>└──────────┬───────────┘<br>│ call.answered, call.hangup webhooks<br>┌──────────────────────┐<br>│ Express / Flask │<br>│ in-memory call_state │<br>└──────────┬───────────┘<br>│ call.recording.saved webhook<br>┌──────────────────────┐<br>│ download audio │<br>│ → Whisper (transcribe)│<br>│ → GPT-4 (respond) │<br>│ → Telnyx speak (TTS) │<br>└──────────────────────┘<br>└──► caller hears the AI response

The demo uses Telnyx for call control, OpenAI for two AI calls (Whisper + GPT-4), and Telnyx again for TTS playback. Two vendors, three AI systems, one webhook.

Set up the project

git clone https://github.com/team-telnyx/telnyx-code-examples.git<br>cd telnyx-code-examples/call-whisper-monitoring-python<br>cp .env.example .env<br># fill in 4 values<br>pip install -r requirements.txt<br>python app.py<br># starts on...