c++ - PortAudio 示例代码问题

Question

我想制作一个吉他效果器程序，所以我尝试从 PORTAUDIO API 运行示例代码 pa_fuzz.c。

它适用于 paWDMKS 主机 api。但是当我使用 Behringer ucg 102(无延迟)连接吉他时，主机 api 更改为 paMME，我收到错误代码 1 和消息:“未定义的外部错误”。同样在 visual studio 输出控制台中，我收到大量消息，例如:

'ConsoleApplication4.exe' (Win32): Unloaded 'C:\Windows\SysWOW64\SHCore.dll'
'ConsoleApplication4.exe' (Win32): Unloaded 'C:\Windows\SysWOW64\shlwapi.dll'
'ConsoleApplication4.exe' (Win32): Unloaded 'C:\Windows\SysWOW64\shell32.dll'
'ConsoleApplication4.exe' (Win32): Unloaded 'C:\Windows\SysWOW64\dbgcore.dll'
'ConsoleApplication4.exe' (Win32): Unloaded 'C:\Program Files\Native Instruments\Rig Kontrol 3 Driver\asio\rig3asio32.dll'

这是“PaHostErrorInfo”对象的代码片段；

PaHostErrorInfo *err2 = Pa_GetLastHostErrorInfo();
    printf(err2->errorText);

这是源代码:

#include <stdio.h>
#include <math.h>
#include "portaudio.h"
/*
** Note that many of the older ISA sound cards on PCs do NOT support
** full duplex audio (simultaneous record and playback).
** And some only support full duplex at lower sample rates.
*/
#define SAMPLE_RATE         (8000)
#define PA_SAMPLE_TYPE      paFloat32
#define FRAMES_PER_BUFFER   (64)

typedef float SAMPLE;

float CubicAmplifier( float input );
static int fuzzCallback( const void *inputBuffer, void *outputBuffer,
                         unsigned long framesPerBuffer,
                         const PaStreamCallbackTimeInfo* timeInfo,
                         PaStreamCallbackFlags statusFlags,
                         void *userData );

/* Non-linear amplifier with soft distortion curve. */
float CubicAmplifier( float input )
{
    float output, temp;
    if( input < 0.0 )
    {
        temp = input + 1.0f;
        output = (temp * temp * temp) - 1.0f;
    }
    else
    {
        temp = input - 1.0f;
        output = (temp * temp * temp) + 1.0f;
    }

    return output;
}
#define FUZZ(x) CubicAmplifier(CubicAmplifier(CubicAmplifier(CubicAmplifier(x))))

static int gNumNoInputs = 0;
/* This routine will be called by the PortAudio engine when audio is needed.
** It may be called at interrupt level on some machines so don't do anything
** that could mess up the system like calling malloc() or free().
*/
static int fuzzCallback( const void *inputBuffer, void *outputBuffer,
                         unsigned long framesPerBuffer,
                         const PaStreamCallbackTimeInfo* timeInfo,
                         PaStreamCallbackFlags statusFlags,
                         void *userData )
{
    SAMPLE *out = (SAMPLE*)outputBuffer;
    const SAMPLE *in = (const SAMPLE*)inputBuffer;
    unsigned int i;
    (void) timeInfo; /* Prevent unused variable warnings. */
    (void) statusFlags;
    (void) userData;

    if( inputBuffer == NULL )
    {
        for( i=0; i<framesPerBuffer; i++ )
        {
            *out++ = 0;  /* left - silent */
            *out++ = 0;  /* right - silent */
        }
        gNumNoInputs += 1;
    }
    else
    {
        for( i=0; i<framesPerBuffer; i++ )
        {
            *out++ = FUZZ(*in++);  /* left - distorted */
            *out++ = *in++;          /* right - clean */
        }
    }

    return paContinue;
}

/*******************************************************************/
int main(void);
int main(void)
{
    PaStreamParameters inputParameters, outputParameters;
    PaStream *stream;
    PaError err;
    PaDeviceInfo *info;
    err = Pa_Initialize();

    if( err != paNoError ) goto error;
    info = Pa_GetDeviceInfo(1);
    inputParameters.device = Pa_GetDefaultInputDevice(); /* default input device */
    if (inputParameters.device == paNoDevice) {
      fprintf(stderr,"Error: No default input device.\n");
      goto error;
    }
    inputParameters.channelCount = 2;       /* stereo input */
    inputParameters.sampleFormat = PA_SAMPLE_TYPE;
    inputParameters.suggestedLatency = Pa_GetDeviceInfo( inputParameters.device )->defaultLowInputLatency;
    inputParameters.hostApiSpecificStreamInfo = NULL;
    info = Pa_GetDeviceInfo(4);
    outputParameters.device = Pa_GetDefaultOutputDevice(); /* default output device */
    if (outputParameters.device == paNoDevice) {
      fprintf(stderr,"Error: No default output device.\n");
      goto error;
    }
    outputParameters.channelCount = 2;       /* stereo output */
    outputParameters.sampleFormat = PA_SAMPLE_TYPE;
    outputParameters.suggestedLatency = Pa_GetDeviceInfo( outputParameters.device )->defaultLowOutputLatency;
    outputParameters.hostApiSpecificStreamInfo = NULL;

    err = Pa_OpenStream(
              &stream,
              &inputParameters,
              &outputParameters,
              SAMPLE_RATE,
              FRAMES_PER_BUFFER,
              0, /* paClipOff, */  /* we won't output out of range samples so don't bother clipping them */
              fuzzCallback,
              NULL );
    PaHostErrorInfo *err2 = Pa_GetLastHostErrorInfo();
    printf(err2->errorText);
    if( err != paNoError ) goto error;

    err = Pa_StartStream( stream );
    if( err != paNoError ) goto error;

    printf("Hit ENTER to stop program.\n");
    getchar();
    err = Pa_CloseStream( stream );
    if( err != paNoError ) goto error;

    printf("Finished. gNumNoInputs = %d\n", gNumNoInputs );
    Pa_Terminate();
    return 0;

error:
    Pa_Terminate();
    fprintf( stderr, "An error occured while using the portaudio stream\n" );
    fprintf( stderr, "Error number: %d\n", err );
    fprintf( stderr, "Error message: %s\n", Pa_GetErrorText( err ) );
    return -1;
}

你们能看看是什么问题吗？我已经安装了 BEHRINGER USB WDM AUDIO 2.8.40 驱动程序。 (我用这个 usb 接口(interface)连接吉他)

Answer 1

我切换到另一个 USB 端口，它工作正常。我认为这是 portaudio 的错误。我会在这里留下这个答案。现在我有另一个问题。延迟 :( 延迟弹吉他真是令人沮丧。这种延迟的原因可能是什么？我正在将我的吉他连接到 behringer ucg102(以无延迟着称)。再一次，我将它与 Guitar Rig 一起使用，延迟接近于 0。这是portaudio库的问题吗？此代码来自他们的示例“pa_fuzz.c”

新编辑:通过选择所需的输入和输出设备解决延迟问题。