列出所有打开的设备 AL 不起作用

Question

我发现了一些声称使用 openAL 列出音频的所有输出设备的示例，但是我只能让它们列出 OSX（Yosemite、Maverick）上当前选择的设备。我使用的是 mac 并具有默认声卡（内置输出）以及一个播放设备和一些声音花设备。

（注意：在 Windows 上，它列出了所有设备）

我希望s = (char *)alcGetString(NULL, ALC_ALL_DEVICES_SPECIFIER);至少列出默认卡和声花设备。它什么都不返回。

s = (char *)alcGetString(NULL, ALC_DEVICE_SPECIFIER); 返回当前选择的设备。

也许虚拟设备存在一些问题？但是，从 mac 设置中选择 soundflower 作为默认输出首先使其显示为“内置输出”。我们还尝试使用外部 DAC 并得到相同的行为。

所有可用输出设备的列表：内置输出

所有可用输入设备的列表：内置麦克风

默认输出设备：内置输出

默认输入设备：内置麦克风

...

这是代码：

#ifdef __APPLE__
# include <OpenAL/al.h>
# include <OpenAL/alc.h>
#else
# include <AL/al.h>
# include <AL/alc.h>
# include <AL/alext.h>
#endif

#ifndef AL_VERSION_1_1
# ifdef __APPLE__
#  include <OpenAL/altypes.h>
#  include <OpenAL/alctypes.h>
#else
#  include <AL/altypes.h>
#  include <AL/alctypes.h>
# endif
#endif

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <string>

using std::string;

#ifndef ALC_ALL_DEVICES_SPECIFIER
# define ALC_ALL_DEVICES_SPECIFIER      0x1013
#endif

#define MAX_DATA    16
static const int indentation = 4;
static const int maxmimumWidth = 79;

void printExtensions (const char *, char, const char *);
void displayDevices(const char *, const char *);
char *getDeviceName(int, char **);
void testForError(void *, const string&);
void testForALCError(ALCdevice *);

int main(int argc, char **argv)
{
  ALCint data[MAX_DATA];
  ALCdevice *device = NULL;
  ALCcontext *context = NULL;
  ALenum error;
  char *s;
  
  if (alcIsExtensionPresent(NULL, "ALC_enumeration_EXT") == AL_TRUE)
  {
    if (alcIsExtensionPresent(NULL, "ALC_enumerate_all_EXT") == AL_FALSE)
      s = (char *)alcGetString(NULL, ALC_DEVICE_SPECIFIER);
    else
      s = (char *)alcGetString(NULL, ALC_ALL_DEVICES_SPECIFIER);
    displayDevices("output", s);
    
    s = (char *)alcGetString(NULL, ALC_CAPTURE_DEVICE_SPECIFIER);
    displayDevices("input", s);
  }
  
  s = getDeviceName(argc, argv);
  device = alcOpenDevice(s);
  testForError(device, "Audio device not available.");
  
  context = alcCreateContext(device, NULL);
  testForError(context, "Unable to create a valid context.");
  
  alcMakeContextCurrent(context);
  testForALCError(device);
  
  s = (char *)alcGetString(device, ALC_DEFAULT_DEVICE_SPECIFIER);
  printf("default output device: %s\n", s);
  testForALCError(device);
  
  error = alcIsExtensionPresent(device, "ALC_EXT_capture");
  if (error)
  {
    s = (char *)alcGetString(device, ALC_CAPTURE_DEFAULT_DEVICE_SPECIFIER);
    printf("default input device:  %s\n", s);
    testForALCError(device);
  }
  printf("capture support: %s\n", (error) ? "yes" : "no");
  
  alcGetIntegerv(device, ALC_FREQUENCY, 1, data);
  printf("mixer frequency: %u hz\n", data[0]);
  testForALCError(device);
  
  alcGetIntegerv(device, ALC_REFRESH, 1, data+1);
  printf("refresh rate : %u hz\n", data[0]/data[1]);
  testForALCError(device);
  
  data[0] = 0;
  alcGetIntegerv(device, ALC_MONO_SOURCES, 1, data);
  error = alcGetError(device);
  if (error == AL_NONE) {
    printf("supported sources; mono: %u, ", data[0]);
    
    data[0] = 0;
    alcGetIntegerv(device, ALC_STEREO_SOURCES, 1, data);
    printf("stereo: %u\n", data[0]);
    testForALCError(device);
  }
  
  printf("ALC version: ");
  alcGetIntegerv(device, ALC_MAJOR_VERSION, 1, data);
  printf("%i.", *data);
  alcGetIntegerv(device, ALC_MINOR_VERSION, 1, data);
  printf("%i\n", *data);
  testForALCError(device);
  
  s = (char *)alcGetString(device, ALC_EXTENSIONS);
  printExtensions ("ALC extensions", ' ', s);
  testForALCError(device);
  
  s = (char *)alGetString(AL_VENDOR);
  error = alGetError();
  if ((error = alGetError()) != AL_NO_ERROR)
    printf("Error #%x: %s\n", error, alGetString(error));
  else
    printf("OpenAL vendor string: %s\n", s);
  
  s = (char *)alGetString(AL_RENDERER);
  if ((error = alGetError()) != AL_NO_ERROR)
    printf("Error #%x: %s\n", error, alGetString(error));
  else
    printf("OpenAL renderer string: %s\n", s);
  
  s = (char *)alGetString(AL_VERSION);
  if ((error = alGetError()) != AL_NO_ERROR)
    printf("Error #%x: %s\n", error, alGetString(error));
  else if (!s)
    printf("Quering AL_VERSION returned NULL pointer!\n");
  else
    printf("OpenAL version string: %s\n", s);
  
  s = (char *)alGetString(AL_EXTENSIONS);
  printExtensions ("OpenAL extensions", ' ', s);
  testForALCError(device);
  
  /* alut testing mechanism */
  context = alcGetCurrentContext();
  if (context == NULL)
  {
    printf("Error: no current context\n");
  }
  else
  {
    if (alGetError () != AL_NO_ERROR)
    {
      printf("Alert: AL error on entry\n");
    }
    else
    {
      if (alcGetError (alcGetContextsDevice (context)) != ALC_NO_ERROR)
      {
        printf("Alert: ALC error on entry\n");
      }
    }
  }
  /* end of alut test */
  
  
  if (alcMakeContextCurrent(NULL) == 0)
    printf("alcMakeContextCurrent failed.\n");
  
  device = alcGetContextsDevice(context);
  alcDestroyContext(context);
  testForALCError(device);
  
  if (alcCloseDevice(device) == 0)
    printf("alcCloseDevice failed.\n");
  
  return 0;
}

/* -------------------------------------------------------------------------- */

void
printChar (int c, int *width)
{
  putchar (c);
  *width = (c == '\n') ? 0 : (*width + 1);
}

void
indent (int *width)
{
  int i;
  for (i = 0; i < indentation; i++)
  {
    printChar (' ', width);
  }
}

void
printExtensions (const char *header, char separator, const char *extensions)
{
  int width = 0, start = 0, end = 0;
  
  printf ("%s:\n", header);
  if (extensions == NULL || extensions[0] == '\0')
  {
    return;
  }
  
  indent (&width);
  while (1)
  {
    if (extensions[end] == separator || extensions[end] == '\0')
    {
      if (width + end - start + 2 > maxmimumWidth)
      {
        printChar ('\n', &width);
        indent (&width);
      }
      while (start < end)
      {
        printChar (extensions[start], &width);
        start++;
      }
      if (extensions[end] == '\0')
      {
        break;
      }
      start++;
      end++;
      if (extensions[end] == '\0')
      {
        break;
      }
      printChar (',', &width);
      printChar (' ', &width);
    }
    end++;
  }
  printChar ('\n', &width);
}

char *
getCommandLineOption(int argc, char **argv, const string& option)
{
  int slen = option.size();
  char *rv = 0;
  int i;
  
  for (i=0; i<argc; i++)
  {
    if (strncmp(argv[i], option.c_str(), slen) == 0)
    {
      i++;
      if (i<argc) rv = argv[i];
    }
  }
  
  return rv;
}

char *
getDeviceName(int argc, char **argv)
{
  static char devname[255];
  int len = 255;
  char *s;
  
  s = getCommandLineOption(argc, argv, "-d");
  if (s)
  {
    strncpy((char *)&devname, s, len);
    len -= strlen(s);
    
    s = getCommandLineOption(argc, argv, "-r");
    if (s)
    {
      strncat((char *)&devname, " on ", len);
      len -= 4;
      
      strncat((char *)&devname, s, len);
    }
    s = (char *)&devname;
  }
  
  return s;
}

void
displayDevices(const char *type, const char *list)
{
  ALCchar *ptr, *nptr;
  
  ptr = (ALCchar *)list;
  printf("list of all available %s devices:\n", type);
  if (!list)
  {
    printf("none\n");
  }
  else
  {
    nptr = ptr;
    while (*(nptr += strlen(ptr)+1) != 0)
    {
      printf("  %s\n", ptr);
      ptr = nptr;
    }
    printf("  %s\n", ptr);
  }
}

void
testForError(void *p, const string& s)
{
  if (p == NULL)
  {
    printf("\nError: %s\n\n", s.c_str());
    exit(-1);
  }
}

void
testForALCError(ALCdevice *device)
{
  ALenum error;
  error = alcGetError(device);
  if (error != ALC_NO_ERROR)
    printf("\nALC Error %x occurred: %s\n", error, alcGetString(device, error));
}