SDL_PauseAudio 声音播放/暂停函数剖析

函数说明

用此函数来暂停播放音频，或播放音频。根据参数来决定， 0是播放音频 ，非0是暂停播放音频切记，并不是停止播放音频！

函数声明

/**
 *  \name Pause audio functions
 *
 *  These functions pause and unpause the audio callback processing.
 *  They should be called with   a parameter of 0 after opening the audio
 *  device to start playing sound.  This is so you can safely initialize
 *  data for your callback function after opening the audio device.
 *  Silence will be written to the audio device during the pause.
 */
/* @{ */
extern DECLSPEC void SDLCALL SDL_PauseAudio(int pause_on);
extern DECLSPEC void SDLCALL SDL_PauseAudioDevice(SDL_AudioDeviceID dev,
                                                  int pause_on);
/* @} *//* Pause audio functions */

函数具体实现

void
SDL_PauseAudioDevice(SDL_AudioDeviceID devid, int pause_on)
{
    SDL_AudioDevice *device = get_audio_device(devid);
    if (device) {
        current_audio.impl.LockDevice(device);
        SDL_AtomicSet(&device->paused, pause_on ? 1 : 0);
        current_audio.impl.UnlockDevice(device);
    }
}

void
SDL_PauseAudio(int pause_on)
{
    SDL_PauseAudioDevice(1, pause_on);
}

代码剖析

关键是设置设备的paused状态，因此，该函数只是做了一个标志位的设置，SDL底层的线程会判断该标志，通过回调函数取音频数据进行播放