Methods of implementing high-performance audio processing functions in embedded systems using C++ language

C language method to implement high-performance audio processing functions in embedded systems

Introduction:
With the development of technology, the application scope of embedded systems It is becoming more and more widespread, especially in fields such as the Internet of Things and smart homes. Audio processing plays an important role in many embedded systems, such as speech recognition, audio playback, etc. This article will introduce how to use C language to implement high-performance audio processing functions in embedded systems and give code examples.

1. Choose the appropriate embedded platform
Hardware resources in embedded systems are limited, so it is very important to choose an embedded platform suitable for audio processing. We need to consider factors such as processor performance, memory capacity, power consumption, etc. You can choose some high-performance embedded processors, such as ARM Cortex-A series. In addition, you should also consider choosing the appropriate audio input and output interface, such as I2S, PCM, etc.

2. Choose a suitable audio processing library
The C language itself does not have built-in audio processing functions, so we need to choose a suitable audio processing library. Some commonly used audio processing libraries are:

1. PortAudio: a cross-platform audio IO library that supports recording and playback functions and can be used in embedded systems.
2. Essentia: An open source audio analysis library that contains many commonly used audio processing algorithms.
3. FFTW: A library for Fourier transform that can implement frequency domain audio processing functions.

Select the appropriate library based on actual application requirements and integrate it into the embedded system. The following example code uses the PortAudio library to implement audio recording and playback functions:

#include <stdio.h>
#include "portaudio.h"

#define SAMPLE_RATE (44100)
#define CHANNEL_COUNT (2)
#define FRAMES_PER_BUFFER (1024)

// 录制回调函数
int recordCallback(const void *inputBuffer, void *outputBuffer,
                    unsigned long framesPerBuffer,
                    const PaStreamCallbackTimeInfo *timeInfo,
                    PaStreamCallbackFlags statusFlags,
                    void *userData)
{
    // 处理录制的音频数据
    // ...

    return 0;
}

// 播放回调函数
int playCallback(const void *inputBuffer, void *outputBuffer,
                unsigned long framesPerBuffer,
                const PaStreamCallbackTimeInfo *timeInfo,
                PaStreamCallbackFlags statusFlags,
                void *userData)
{
    // 生成播放的音频数据
    // ...

    return 0;
}

int main()
{
    PaStream *recordingStream;
    PaStream *playingStream;
    PaError err;

    // 初始化PortAudio库
    err = Pa_Initialize();
    if (err != paNoError)
    {
        printf("Failed to initialize PortAudio
");
        return 0;
    }

    // 打开录制流
    err = Pa_OpenDefaultStream(&recordingStream, CHANNEL_COUNT, 0, paFloat32,
                                SAMPLE_RATE, FRAMES_PER_BUFFER,
                                recordCallback, NULL);
    if (err != paNoError)
    {
        printf("Failed to open recording stream
");
        return 0;
    }

    // 打开播放流
    err = Pa_OpenDefaultStream(&playingStream, 0, CHANNEL_COUNT, paFloat32,
                                SAMPLE_RATE, FRAMES_PER_BUFFER,
                                NULL, playCallback);
    if (err != paNoError)
    {
        printf("Failed to open playing stream
");
        return 0;
    }

    // 启动录制流
    err = Pa_StartStream(recordingStream);
    if (err != paNoError)
    {
        printf("Failed to start recording stream
");
        return 0;
    }

    // 启动播放流
    err = Pa_StartStream(playingStream);
    if (err != paNoError)
    {
        printf("Failed to start playing stream
");
        return 0;
    }

    // 等待用户按下回车键停止程序
    getchar();

    // 停止录制流
    err = Pa_StopStream(recordingStream);
    if (err != paNoError)
    {
        printf("Failed to stop recording stream
");
        return 0;
    }

    // 停止播放流
    err = Pa_StopStream(playingStream);
    if (err != paNoError)
    {
        printf("Failed to stop playing stream
");
        return 0;
    }

    // 关闭录制流
    err = Pa_CloseStream(recordingStream);
    if (err != paNoError)
    {
        printf("Failed to close recording stream
");
        return 0;
    }

    // 关闭播放流
    err = Pa_CloseStream(playingStream);
    if (err != paNoError)
    {
        printf("Failed to close playing stream
");
        return 0;
    }

    // 终止PortAudio库
    err = Pa_Terminate();
    if (err != paNoError)
    {
        printf("Failed to terminate PortAudio
");
        return 0;
    }

    return 0;
}

3. Optimization algorithm and code
In embedded systems, resources are limited, and it is necessary to ensure the audio processing function while Minimize the amount of calculation and memory usage. Algorithms and codes can be optimized through the following methods:

1. Use fixed-point calculations: Embedded systems have limited performance, and using floating-point calculations will consume a lot of time and memory. You can use a fixed number of points for calculations to improve performance.
2. Use efficient audio algorithms: Choosing efficient audio algorithms can reduce the amount of calculation and memory usage. For example, the Fast Fourier Transform (FFT) algorithm is used to implement frequency domain audio processing.
3. Reasonable use of buffers: During audio processing, use buffers appropriately to store data, reduce the number of accesses to external memory, and improve efficiency.

Conclusion:
This article introduces the method of using C language to implement high-performance audio processing functions in embedded systems. By selecting the appropriate embedded platform and audio processing library, and optimizing the algorithm and code, fast, efficient, and stable audio processing functions can be achieved. I hope this article can be helpful to audio processing engineers in embedded systems.

References:

1. PortAudio official documentation: http://www.portaudio.com/
2. Essentia official documentation: http://essentia.upf. edu/
3. FFTW official documentation: http://www.fftw.org/

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