public bool SetDevice(ushort sampleRate, ushort bufferSize, Func <byte> getSample)
{
GetSample = getSample;
SDL.SDL_AudioSpec wanted = new SDL.SDL_AudioSpec();
sudata sud = new sudata();
bool result = false;
wanted.freq = sampleRate;
wanted.samples = bufferSize;
wanted.channels = 1;
wanted.format = SDL.AUDIO_S16;
wanted.userdata = Marshal.AllocHGlobal(Marshal.SizeOf(sud));
wanted.callback = pFillAudio;
if ((SDL.SDL_InitSubSystem(SDL.SDL_INIT_AUDIO)) == 0)
{
if ((SDL.SDL_OpenAudio(ref wanted, out sud.obtained)) == 0)
{
result = true;
}
}
if (result == false)
{
Log.Write($"Couldn't open audio: {SDL.SDL_GetError()}");
Marshal.FreeHGlobal(wanted.userdata);
return(false);
}
sud.bsize = sud.obtained.size;
sud.buf = Marshal.AllocHGlobal((int)sud.bsize);
sud.lp_fltr = Calc.bqd_lp_init(sud.obtained.freq, 4000).ToPointer();
sud.hp_fltr = Calc.bqd_hp_init(sud.obtained.freq, 1000).ToPointer();
Marshal.StructureToPtr(sud, wanted.userdata, false);
IsWaveDeviceAvailable = true;
return(result);
}
private static void FillAudio(IntPtr udata, IntPtr stream, int len)
{
sudata sud = udata.ToStruct <sudata>();
if (len > sud.bsize)
{
Log.Write("fill_audio: OUCH, len > bsize!");
len = (int)sud.bsize;
}
StdLib.MemSet(stream, sud.obtained.silence, len);
for (int i = 0; i < len / sizeof(short); i++)
{
bqd_filter hp_fltr = sud.hp_fltr.ToStruct <bqd_filter>();
bqd_filter lp_fltr = sud.lp_fltr.ToStruct <bqd_filter>();
double sample = GetSample();
sample = Calc.bqd_apply(ref hp_fltr, (sample - 127.0) * 128.0);
sample = Calc.bqd_apply(ref lp_fltr, sample);
Marshal.WriteInt16(sud.buf, i * sizeof(short), (short)Math.Round(sample));
}
SDL.SDL_MixAudioFormat(stream, sud.buf, sud.obtained.format, (uint)len, SDL.SDL_MIX_MAXVOLUME);
}
