0

我想知道如何知道 portaudio 测试示例的关系以及如何获得频率。我想知道如何将特定频率发送到声卡？1. 如何知道代码发送到声卡的具体频率 2. 我如何发送 sin(2*pi*f*t) 和 sin((2*pi*f*t)-3.14) 这是一个延迟版本。这是代码。非常感谢任何帮助

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

#define NUM_SECONDS   (20)
#define SAMPLE_RATE   (44100)
#define AMPLITUDE     (0.9)
#define FRAMES_PER_BUFFER  (64)
#define OUTPUT_DEVICE Pa_GetDefaultOutputDeviceID()
//#define OUTPUT_DEVICE (2)

#ifndef M_PI
#define M_PI  (3.14159265)
#endif

#define TABLE_SIZE   (200)
typedef struct
{
    float sine[TABLE_SIZE];
     int left_phase;
    int right_phase;
}
paTestData;
static int patestCallback(   void *inputBuffer, void *outputBuffer,
                             unsigned long framesPerBuffer,
                             PaTimestamp outTime, void *userData )
{
    paTestData *data = (paTestData*)userData;
    float *out = (float*)outputBuffer;
    unsigned long i;
    int finished = 0;
    (void) outTime; /* Prevent unused variable warnings. */
    (void) inputBuffer;
    for( i=0; i<framesPerBuffer; i++ )
    {
        *out++ = data->sine[data->left_phase];  /* left */
        *out++ = data->sine[data->right_phase];  /* right */
        data->left_phase += 1;
    if( data->left_phase >= TABLE_SIZE ) data->left_phase -= TABLE_SIZE;
    data->right_phase +=2.57; /* higher pitch so we can distinguish left and right. */
    if( data->right_phase >= TABLE_SIZE ) data->right_phase -= TABLE_SIZE;
}
return finished;

}

/*******************************************************************/
int main(void);
int main(void)
{
PortAudioStream *stream;
PaError err;
paTestData data;
int i;
printf("PortAudio Test: output sine wave. SR = %d, BufSize = %d, devID = %d\n",
    SAMPLE_RATE, FRAMES_PER_BUFFER, OUTPUT_DEVICE);
/* initialise sinusoidal wavetable */
for( i=0; i<TABLE_SIZE; i++ )
{
    data.sine[i] = (float) (AMPLITUDE * sin( ((double)i/(double)TABLE_SIZE) * M_PI * 2. ));
}
data.left_phase = data.right_phase = 0;
err = Pa_Initialize();
if( err != paNoError ) goto error;
err = Pa_OpenStream(
          &stream,
          paNoDevice,/* default input device */
          0,              /* no input */
          paFloat32,  /* 32 bit floating point input */
          NULL,
          OUTPUT_DEVICE,
          2,          /* stereo output */
          paFloat32,      /* 32 bit floating point output */
          NULL,
          SAMPLE_RATE,
          FRAMES_PER_BUFFER,
          0,              /* number of buffers, if zero then use default minimum */
          paClipOff,      /* we won't output out of range samples so don't bother clipping them */
          patestCallback,
          &data );
if( err != paNoError ) goto error;
err = Pa_StartStream( stream );
if( err != paNoError ) goto error;
printf("Play for %d seconds.\n", NUM_SECONDS ); fflush(stdout);
Pa_Sleep( NUM_SECONDS * 1000 );

err = Pa_StopStream( stream );
if( err != paNoError ) goto error;
err = Pa_CloseStream( stream );
if( err != paNoError ) goto error;
Pa_Terminate();
printf("Test finished.\n");
return err;

错误：Pa_Terminate(); fprintf( stderr, "使用 portaudio 流时出错\n" ); fprintf(stderr, "错误号: %d\n", err ); fprintf(stderr, "错误信息: %s\n", Pa_GetErrorText( err ) ); 返回错误；}

4

1 回答 1

2

快速浏览一下，SAMPLE_RATE / TABLE_SIZE 将为您提供正弦波的每秒周期数，这似乎是 ~220Hz，这是一个 A3 音符。虽然从代码中我可以看到左声道正在接收这个波，而右声道正在以 2.75 倍的基本速率在表格中步进，我猜这将是大约 606Hz 没有击中音符，我希望这个样本听起来很可怕！

要发送正弦波和延迟版本，您只需使用相位参数的偏移量查找延迟版本，注意正确环绕，并将波加在一起。您可能需要降低 AMPLITUDE 以避免削波。

于 2013-10-03T07:35:56.417 回答