ref: e33a4961331301b1e3a5c65d148050fa33c4c594
dir: /opl/opl_sdl.c/
// Emacs style mode select -*- C++ -*-
//-----------------------------------------------------------------------------
//
// Copyright(C) 2009 Simon Howard
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
// 02111-1307, USA.
//
// DESCRIPTION:
// OPL SDL interface.
//
//-----------------------------------------------------------------------------
#include "config.h"
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include "SDL.h"
#include "SDL_mixer.h"
#include "fmopl.h"
#include "opl.h"
#include "opl_internal.h"
#include "opl_queue.h"
// TODO:
#define opl_sample_rate 22050
// When the callback mutex is locked using OPL_Lock, callback functions
// are not invoked.
static SDL_mutex *callback_mutex = NULL;
// Queue of callbacks waiting to be invoked.
static opl_callback_queue_t *callback_queue;
// Mutex used to control access to the callback queue.
static SDL_mutex *callback_queue_mutex = NULL;
// Current time, in number of samples since startup:
static int current_time;
// OPL software emulator structure.
static FM_OPL *opl_emulator = NULL;
// Temporary mixing buffer used by the mixing callback.
static int16_t *mix_buffer = NULL;
// SDL parameters.
static int sdl_was_initialised = 0;
static int mixing_freq, mixing_channels;
static Uint16 mixing_format;
static int SDLIsInitialised(void)
{
int freq, channels;
Uint16 format;
return Mix_QuerySpec(&freq, &format, &channels);
}
// Advance time by the specified number of samples, invoking any
// callback functions as appropriate.
static void AdvanceTime(unsigned int nsamples)
{
opl_callback_t callback;
void *callback_data;
SDL_LockMutex(callback_queue_mutex);
// Advance time.
current_time += nsamples;
// Are there callbacks to invoke now? Keep invoking them
// until there are none more left.
while (!OPL_Queue_IsEmpty(callback_queue)
&& current_time >= OPL_Queue_Peek(callback_queue))
{
// Pop the callback from the queue to invoke it.
if (!OPL_Queue_Pop(callback_queue, &callback, &callback_data))
{
break;
}
// The mutex stuff here is a bit complicated. We must
// hold callback_mutex when we invoke the callback (so that
// the control thread can use OPL_Lock() to prevent callbacks
// from being invoked), but we must not be holding
// callback_queue_mutex, as the callback must be able to
// call OPL_SetCallback to schedule new callbacks.
SDL_UnlockMutex(callback_queue_mutex);
SDL_LockMutex(callback_mutex);
callback(callback_data);
SDL_UnlockMutex(callback_mutex);
SDL_LockMutex(callback_queue_mutex);
}
SDL_UnlockMutex(callback_queue_mutex);
}
// Call the OPL emulator code to fill the specified buffer.
static void FillBuffer(int16_t *buffer, unsigned int nsamples)
{
unsigned int i;
// This seems like a reasonable assumption. mix_buffer is
// 1 second long, which should always be much longer than the
// SDL mix buffer.
assert(nsamples < mixing_freq);
YM3812UpdateOne(opl_emulator, mix_buffer, nsamples, 0);
// Mix into the destination buffer, doubling up into stereo.
for (i=0; i<nsamples; ++i)
{
buffer[i * 2] += mix_buffer[i] / 2;
buffer[i * 2 + 1] += mix_buffer[i] / 2;
}
}
// Callback function to fill a new sound buffer:
static void OPL_Mix_Callback(void *udata,
Uint8 *byte_buffer,
int buffer_bytes)
{
int16_t *buffer;
unsigned int buffer_len;
unsigned int filled = 0;
// Buffer length in samples (quadrupled, because of 16-bit and stereo)
buffer = (int16_t *) byte_buffer;
buffer_len = buffer_bytes / 4;
// Repeatedly call the FMOPL update function until the buffer is
// full.
while (filled < buffer_len)
{
unsigned int next_callback_time;
unsigned int nsamples;
SDL_LockMutex(callback_queue_mutex);
// Work out the time until the next callback waiting in
// the callback queue must be invoked. We can then fill the
// buffer with this many samples.
if (OPL_Queue_IsEmpty(callback_queue))
{
nsamples = buffer_len - filled;
}
else
{
next_callback_time = OPL_Queue_Peek(callback_queue);
nsamples = next_callback_time - current_time;
if (nsamples > buffer_len - filled)
{
nsamples = buffer_len - filled;
}
}
SDL_UnlockMutex(callback_queue_mutex);
// Add emulator output to buffer.
FillBuffer(buffer + filled * 2, nsamples);
filled += nsamples;
// Invoke callbacks for this point in time.
AdvanceTime(nsamples);
}
}
static void OPL_SDL_Shutdown(void)
{
if (sdl_was_initialised)
{
Mix_CloseAudio();
SDL_QuitSubSystem(SDL_INIT_AUDIO);
OPL_Queue_Destroy(callback_queue);
free(mix_buffer);
sdl_was_initialised = 0;
}
if (opl_emulator != NULL)
{
OPLDestroy(opl_emulator);
opl_emulator = NULL;
}
if (callback_mutex != NULL)
{
SDL_DestroyMutex(callback_mutex);
callback_mutex = NULL;
}
if (callback_queue_mutex != NULL)
{
SDL_DestroyMutex(callback_queue_mutex);
callback_queue_mutex = NULL;
}
}
static int OPL_SDL_Init(unsigned int port_base)
{
// Check if SDL_mixer has been opened already
// If not, we must initialise it now
if (!SDLIsInitialised())
{
if (SDL_Init(SDL_INIT_AUDIO) < 0)
{
fprintf(stderr, "Unable to set up sound.\n");
return 0;
}
if (Mix_OpenAudio(opl_sample_rate, AUDIO_S16SYS, 2, 1024) < 0)
{
fprintf(stderr, "Error initialising SDL_mixer: %s\n", Mix_GetError());
SDL_QuitSubSystem(SDL_INIT_AUDIO);
return 0;
}
SDL_PauseAudio(0);
// When this module shuts down, it has the responsibility to
// shut down SDL.
sdl_was_initialised = 1;
}
else
{
sdl_was_initialised = 0;
}
// Queue structure of callbacks to invoke.
callback_queue = OPL_Queue_Create();
current_time = 0;
// Get the mixer frequency, format and number of channels.
Mix_QuerySpec(&mixing_freq, &mixing_format, &mixing_channels);
// Only supports AUDIO_S16SYS
if (mixing_format != AUDIO_S16SYS || mixing_channels != 2)
{
fprintf(stderr,
"OPL_SDL only supports native signed 16-bit LSB, "
"stereo format!\n");
OPL_SDL_Shutdown();
return 0;
}
// Mix buffer:
mix_buffer = malloc(mixing_freq * 2);
// Create the emulator structure:
opl_emulator = makeAdlibOPL(mixing_freq);
if (opl_emulator == NULL)
{
fprintf(stderr, "Failed to initialise software OPL emulator!\n");
OPL_SDL_Shutdown();
return 0;
}
callback_mutex = SDL_CreateMutex();
callback_queue_mutex = SDL_CreateMutex();
// TODO: This should be music callback? or-?
Mix_SetPostMix(OPL_Mix_Callback, NULL);
return 1;
}
static unsigned int OPL_SDL_PortRead(opl_port_t port)
{
if (opl_emulator != NULL)
{
return OPLRead(opl_emulator, port);
}
else
{
return 0;
}
}
static void OPL_SDL_PortWrite(opl_port_t port, unsigned int value)
{
if (opl_emulator != NULL)
{
OPLWrite(opl_emulator, port, value);
}
}
static void OPL_SDL_SetCallback(unsigned int ms,
opl_callback_t callback,
void *data)
{
SDL_LockMutex(callback_queue_mutex);
OPL_Queue_Push(callback_queue, callback, data,
current_time + (ms * mixing_freq) / 1000);
SDL_UnlockMutex(callback_queue_mutex);
}
static void OPL_SDL_Lock(void)
{
SDL_LockMutex(callback_mutex);
}
static void OPL_SDL_Unlock(void)
{
SDL_UnlockMutex(callback_mutex);
}
opl_driver_t opl_sdl_driver =
{
"SDL",
OPL_SDL_Init,
OPL_SDL_Shutdown,
OPL_SDL_PortRead,
OPL_SDL_PortWrite,
OPL_SDL_SetCallback,
OPL_SDL_Lock,
OPL_SDL_Unlock
};