/* game provides us mono samples, we need stereo */
static int16_t rb_soundbuf [MAX_SOUNDBUF_SIZE * 2];
static int8_t temp_soundbuf[MAX_SOUNDBUF_SIZE];
static void get_more(const void** start, size_t* size)
{
    if(audio_sys->settings.sound_enabled && audio_callback)
    {
        audio_callback(audio_param, temp_soundbuf, audio_sys->settings.sound_bufsize);
        /* convert xworld format (signed 8-bit) to rockbox format (stereo signed 16-bit) */
        for(int i = 0; i < audio_sys->settings.sound_bufsize; i += 2)
        {
            rb_soundbuf[i] = temp_soundbuf[i] * 0x100; /* mirror left/right channels */
            rb_soundbuf[i+1] = rb_soundbuf[i];
        }
        *start = rb_soundbuf;
        *size = audio_sys->settings.sound_bufsize * 2 * sizeof(int16_t);
    }
    else
    {
        rb->memset(rb_soundbuf, 0, audio_sys->settings.sound_bufsize * 2 * sizeof(int16_t));
        *start = rb_soundbuf;
        *size = audio_sys->settings.sound_bufsize * 2 * sizeof(int16_t);
    }
}