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Audio / How to process audio recording and manage graphic in (almost) real time ?

« on: June 14, 2020, 07:28:08 pm »

Hello !

I am building a music visualizer. I already made the analyser, but I load the music using a buffer with the function LoadFromFile. Here is what it looks like :


Now I would like to use the internal input of my sound card for the sound input, to be able to display this animation live during parties and live dj set.

So I begun looking at the Audio Recording part of SFML, and made this little code to test it :

Code: [Select]

#include <SFML/Audio.hpp>
#include <SFML/Graphics.hpp>

using namespace  std;



void drawSamples(const sf::Int16* samples, sf::Uint64 samplecount, sf::RenderWindow &window){

    sf::VertexArray Lines;
    Lines.setPrimitiveType(sf::LineStrip);
    for(int i = 0;i < samplecount;i++){
        Lines.append(sf::Vertex(sf::Vector2f(i,samples[i]/100+window.getSize().y/2),sf::Color::White));
    }

    window.draw(Lines);

}

int main()
{

    sf::RenderWindow window(sf::VideoMode(1440,900,32),"TEST RECORDER");
    sf::SoundBufferRecorder recorder;
    sf::SoundBuffer buffer;
    sf::Event event;


    //Make sure there is something in the buffer
    recorder.start();
    sf::sleep(sf::milliseconds(1));
    recorder.stop();



    while(window.isOpen()){

        while(window.pollEvent(event)){
            switch (event.type)
            {
            case sf::Event::EventType::Closed:
                window.close();
                break;
            }

        }
        recorder.stop();
        buffer = recorder.getBuffer();
        window.clear(sf::Color::Black);
        const sf::Int16* samples = buffer.getSamples();
        sf::Uint64 samplecount = buffer.getSampleCount();
        drawSamples(samples, samplecount, window);
        window.display();
        recorder.start();
    }
    return 0;
}




When I run it, I find it really slow. I would like to hit almost 60fps to be able to run it smoothly on a video projector.
Where do you think this slowness comes from ? Is it because the recording is taking a lot of time ? Is it because of the the fact that I copy the buffer every time ?

There is another part in this problem. To achieve a very good looking results like the one on the video I use a bufferSize of  2^13 (8192) integer. I guess if I want to run my program with a live sound source I need to be able to get that data fast enough so that it won’t interfere with the displaying.
What should I use ? I feel like I should use a custom recorder that is fast enough, but I also feel like this should use an audio stream because I want to load some data that cannot be loaded directly in memory (because it doesn’t exist yet…). I would like to know if recording with a SoundBufferRecorder is a good solution to provide data for an audio stream.

I hope my problem appears clear to you, and I say thanks in advance to anyone willing to help me !

Thanks,

Louis