Implementing a real-time audio streamer in C++

03 Oct 2023

Streaming audio in real-time can be a challenging task, but with the right tools and knowledge, it is achievable. In this blog post, we will walk through the steps of implementing a real-time audio streamer in C++.

Setting up the Environment

Before we start coding, we need to set up the environment by installing the required libraries and dependencies. For our audio streaming application, we will be using the PortAudio library, which provides a platform-independent audio I/O API.

To install PortAudio, you can follow the instructions provided in their official documentation. Make sure to download and install the appropriate version for your operating system.

Creating the Audio Streamer

Let’s create a simple audio streamer that captures audio from the microphone and plays it back in real-time. Here’s a step-by-step guide:

Step 1: Initializing PortAudio

#include <portaudio.h>

// Initialize PortAudio
Pa_Initialize();

Step 2: Setting up Audio Input and Output

PaStreamParameters inputParameters, outputParameters;
PaStream *stream;
PaError err;

// Set up the input parameters
inputParameters.device = Pa_GetDefaultInputDevice();
inputParameters.channelCount = 1;
inputParameters.sampleFormat = paFloat32;
inputParameters.suggestedLatency = Pa_GetDeviceInfo(inputParameters.device)->defaultLowInputLatency;
inputParameters.hostApiSpecificStreamInfo = NULL;

// Set up the output parameters
outputParameters.device = Pa_GetDefaultOutputDevice();
outputParameters.channelCount = 1;
outputParameters.sampleFormat = paFloat32;
outputParameters.suggestedLatency = Pa_GetDeviceInfo(outputParameters.device)->defaultLowOutputLatency;
outputParameters.hostApiSpecificStreamInfo = NULL;

// Open the audio stream
err = Pa_OpenStream(&stream, &inputParameters, &outputParameters, SAMPLE_RATE, FRAMES_PER_BUFFER, paClipOff, NULL, NULL);

if (err != paNoError) {
    // Handle the error
    return err;
}

Step 3: Starting the Audio Stream

// Start the audio stream
err = Pa_StartStream(stream);

if (err != paNoError) {
    // Handle the error
    return err;
}

Step 4: Processing Audio Data

// Define an audio buffer
float buffer[FRAMES_PER_BUFFER];

while (stream is running) {

    // Read audio data from the input stream
    err = Pa_ReadStream(stream, buffer, FRAMES_PER_BUFFER);
    
    if (err != paNoError) {
        // Handle the error
        return err;
    }

    // Process the audio data (e.g., apply effects, analyze, etc.)
    
    // Write audio data to the output stream
    err = Pa_WriteStream(stream, buffer, FRAMES_PER_BUFFER);

    if (err != paNoError) {
        // Handle the error
        return err;
    }
}

Step 5: Stopping and Closing the Audio Stream

// Stop the audio stream
err = Pa_StopStream(stream);

if (err != paNoError) {
    // Handle the error
    return err;
}

// Close the audio stream
err = Pa_CloseStream(stream);

if (err != paNoError) {
    // Handle the error
    return err;
}

Conclusion

In this blog post, we have explored the process of implementing a real-time audio streamer in C++. We learned how to set up the environment, initialize PortAudio, and create an audio stream for capturing and playing back audio in real-time. With this knowledge, you can now build upon this foundation to create more complex audio streaming applications.

#streamingaudio #C++