Welcome back! In the previous lesson, we set up a Java development environment using Gradle and added the necessary dependencies to interact with the OpenAI API. Today, we're going to make your first API request to the GPT-4o Mini Transcribe API, which is essential for building a transcription system. This lesson builds on your understanding of Java project setup and making basic HTTP requests, and now we’ll focus on interacting with APIs.

You'll learn how to send audio data to the GPT-4o Mini Transcribe API and receive a transcription in return.

The GPT-4o Mini Transcribe API from OpenAI is designed to handle audio transcription. The main idea is to send audio data to the API, which then returns the transcribed text. To do this, you need a valid API key to authenticate your requests. The API processes audio files sent as byte streams, transcribing spoken content into text.

GPT-4o Mini Transcribe is optimized for capturing spoken words and may skip nonverbal sounds, ensuring the output is clear and human-readable. The response is typically a JSON object containing the transcribed text and sometimes additional details, such as the duration of the audio.

Let's break down the process of making a transcription request into smaller, manageable steps. We'll look at each part of the code and explain what it does.

First, we need to load our API key and set up the OpenAI client. This ensures our requests are authenticated and sent to the correct endpoint.

Explanation:

• Loads the API key and base URL from a .env file or environment variables.
• Throws an error if the API key is missing.
• Creates an OpenAIClient instance for making API requests.

Before sending the audio file, we need to check that it exists, is readable, and is not empty.

Explanation:

• Converts the file path string to a Path and then to a File.
• Checks if the file exists, is readable, and is not empty.
• Throws descriptive errors if any check fails.

Now, we build the parameters for the transcription request.

Explanation:

• Uses the builder pattern to specify the audio file and the model name (gpt-4o-mini).
• Prepares the parameters needed for the API call.

We send the request to the API and handle the response.

Explanation:

• Sends the transcription request using the OpenAI client.
• Extracts the transcribed text from the response.
• Checks if the response contains text and prints it.

You can organize the above steps into a class for reuse:

Explanation:

• Encapsulates the logic in a reusable class.
• The main method demonstrates how to use the class to transcribe an audio file.

Now that you know how to make an API request to the GPT-4o Mini Transcribe API using the OpenAI Java SDK, it's time to practice! Try transcribing your own audio files and see the results.