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| You can add your code example here | SDL_AudioSpec want, have; SDL_AudioDeviceID dev; SDL_zero(want); want.freq = 48000; want.format = AUDIO_F32; want.channels = 2; want.samples = 4096; want.callback = MyAudioCallback; // you wrote this function elsewhere. dev = SDL_OpenAudioDevice(NULL, 0, &want, &have, SDL_AUDIO_ALLOW_FORMAT_CHANGE); if (dev == 0) { printf("Failed to open audio: %s\n", SDL_GetError()); } else { if (have.format != want.format) // we let this one thing change. printf("We didn't get Float32 audio format.\n"); SDL_PauseAudioDevice(dev, 0); // start audio playing. SDL_Delay(5000); // let the audio callback play some sound for 5 seconds. SDL_CloseAudioDevice(dev); } |
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| [[SDL_OpenAudio]](), unlike this function, always acts on device ID 1. As such, this function will never return a 1 so as not to conflict with the legacy function. Please note that SDL 2.0 does not support recording yet; as such, this function will fail if '''iscapture''' is not zero. In the future, when recording is implemented, this value can be non-zero. |
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| For example, if you ask for float32 audio format, but the sound card only supports int16, SDL will set the hardware to int16. If SDL_AUDIO_ALLOW_FORMAT_CHANGE is set, SDL will change the format in the '''obtained''' structure. If the SDL_AUDIO_ALLOW_FORMAT_CHANGE is ''not'' set, SDL will prepare to convert your callback's float32 audio to int16 before feeding it to the hardware. | For example, if you ask for float32 audio format, but the sound card only supports int16, SDL will set the hardware to int16. If you had set SDL_AUDIO_ALLOW_FORMAT_CHANGE, SDL will change the format in the '''obtained''' structure. If that flag was ''not'' set, SDL will prepare to convert your callback's float32 audio to int16 before feeding it to the hardware and will keep the originally requested format in the '''obtained''' structure. |
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| [[SDL_OpenAudio]](), unlike this function, always acts on device ID 1. As such, this function will never return a 1 so as not to conflict with the legacy function. | If your application can only handle one specific data format, pass a zero for '''allowed_changes''' and let SDL transparently handle any differences. |
SDL_OpenAudioDevice
Use this function to open a specific audio device.
Contents
Syntax
SDL_AudioDeviceID SDL_OpenAudioDevice(const char* device,
int iscapture,
const SDL_AudioSpec* desired,
SDL_AudioSpec* obtained,
int allowed_changes)
Function Parameters
device |
a UTF-8 string reported by SDL_GetAudioDeviceName(); see Remarks |
iscapture |
non-zero to specify a device should be opened for recording, not playback. |
desired |
the desired audio parameters -or- an SDL_AudioSpec structure representing the desired output format; see SDL_OpenAudio() for more information |
obtained |
an SDL_AudioSpec structure filled in with the actual output format; see SDL_OpenAudio() for more information |
allowed_changes |
0, or one or more flags OR'd together; see Remarks for details |
Return Value
Returns a valid device ID that is > 0 on success or 0 on failure; call SDL_GetError() for more information.
For compatibility with SDL 1.2, this will never return 1, since SDL reserves that ID for the legacy SDL_OpenAudio() function.
Code Examples
SDL_AudioSpec want, have;
SDL_AudioDeviceID dev;
SDL_zero(want);
want.freq = 48000;
want.format = AUDIO_F32;
want.channels = 2;
want.samples = 4096;
want.callback = MyAudioCallback; // you wrote this function elsewhere.
dev = SDL_OpenAudioDevice(NULL, 0, &want, &have, SDL_AUDIO_ALLOW_FORMAT_CHANGE);
if (dev == 0) {
printf("Failed to open audio: %s\n", SDL_GetError());
} else {
if (have.format != want.format) // we let this one thing change.
printf("We didn't get Float32 audio format.\n");
SDL_PauseAudioDevice(dev, 0); // start audio playing.
SDL_Delay(5000); // let the audio callback play some sound for 5 seconds.
SDL_CloseAudioDevice(dev);
}
Remarks
SDL_OpenAudio(), unlike this function, always acts on device ID 1. As such, this function will never return a 1 so as not to conflict with the legacy function.
Please note that SDL 2.0 does not support recording yet; as such, this function will fail if iscapture is not zero. In the future, when recording is implemented, this value can be non-zero.
Passing in a device name of NULL requests the most reasonable default (and is equivalent to what SDL_OpenAudio() does to choose a device). The device name is a UTF-8 string reported by SDL_GetAudioDeviceName(), but some drivers allow arbitrary and driver-specific strings, such as a hostname/IP address for a remote audio server, or a filename in the diskaudio driver.
allowed_changes can have the following flags OR'd together:
SDL_AUDIO_ALLOW_FREQUENCY_CHANGE |
SDL_AUDIO_ALLOW_FORMAT_CHANGE |
SDL_AUDIO_ALLOW_CHANNELS_CHANGE |
SDL_AUDIO_ALLOW_ANY_CHANGE |
These flags specify how SDL should behave when a device cannot offer a specific feature. If the application requests a feature that the hardware doesn't offer, SDL will always try to get the closest equivalent.
For example, if you ask for float32 audio format, but the sound card only supports int16, SDL will set the hardware to int16. If you had set SDL_AUDIO_ALLOW_FORMAT_CHANGE, SDL will change the format in the obtained structure. If that flag was not set, SDL will prepare to convert your callback's float32 audio to int16 before feeding it to the hardware and will keep the originally requested format in the obtained structure.
If your application can only handle one specific data format, pass a zero for allowed_changes and let SDL transparently handle any differences.
