aiie/sdl/sdl-speaker.cpp
2020-06-27 18:00:59 -04:00

226 lines
6.2 KiB
C++

#include "sdl-speaker.h"
#include <pthread.h>
#include <unistd.h>
extern "C"
{
#include <SDL.h>
#include <SDL_thread.h>
};
#include "globals.h"
#include "timeutil.h"
// FIXME: 4096 is the right value here, I'm just debugging
#define SDLSIZE (4096)
// FIXME: Globals; ick.
static volatile uint32_t bufIdx = 0;
static uint8_t soundBuf[44100];
static pthread_mutex_t togmutex = PTHREAD_MUTEX_INITIALIZER;
static struct timespec sdlEmptyTime, sdlStartTime;
extern struct timespec startTime; // defined in aiie (main)
static void audioCallback(void *unused, Uint8 *stream, int len)
{
pthread_mutex_lock(&togmutex);
if (g_biosInterrupt) {
// While the BIOS is running, we don't put samples in the audio
// queue.
memset(stream, 0x80, len);
pthread_mutex_unlock(&togmutex);
return;
}
// calculate when the buffer will be empty again
do_gettime(&sdlEmptyTime);
timespec_add_us(&sdlEmptyTime, ((float)len * (float)1000000)/(float)44100, &sdlEmptyTime);
sdlEmptyTime = tsSubtract(sdlEmptyTime, sdlStartTime);
static uint8_t lastKnownSample = 0; // saved for when the apple is quiescent
if (bufIdx >= len) {
memcpy(stream, soundBuf, len);
lastKnownSample = stream[len-1];
if (bufIdx > len) {
// move the remaining data down
memcpy(soundBuf, &soundBuf[len], bufIdx - len + 1);
bufIdx -= len;
}
} else {
if (bufIdx) {
// partial buffer exists
memcpy(stream, soundBuf, bufIdx);
// and it's a partial underrun
memset(&stream[bufIdx], lastKnownSample, len-bufIdx);
bufIdx = 0;
} else {
// Total audio underrun. This is normal if nothing is toggling the
// speaker; we stay at the last known level.
memset(stream, lastKnownSample, len);
}
}
pthread_mutex_unlock(&togmutex);
}
void ResetDCFilter(); // FIXME: remove
SDLSpeaker::SDLSpeaker()
{
toggleState = false;
mixerValue = 0x80;
pthread_mutex_init(&togmutex, NULL);
_init_darwin_shim();
ResetDCFilter();
lastCycleCount = 0;
lastSampleCount = 0;
}
SDLSpeaker::~SDLSpeaker()
{
}
void SDLSpeaker::begin()
{
do_gettime(&sdlStartTime);
do_gettime(&sdlEmptyTime);
sdlEmptyTime = tsSubtract(sdlEmptyTime, sdlStartTime);
SDL_AudioSpec audioDevice;
SDL_AudioSpec audioActual;
SDL_memset(&audioDevice, 0, sizeof(audioDevice));
audioDevice.freq = 44100; // count of 8-bit samples
audioDevice.format = AUDIO_U8;
audioDevice.channels = 1;
audioDevice.samples = SDLSIZE; // SDLSIZE 8-bit samples @ 44100Hz: 4096 is about 1/10th second out of sync
audioDevice.callback = audioCallback;
audioDevice.userdata = NULL;
memset(&soundBuf[0], 0, SDLSIZE);
bufIdx = SDLSIZE/2; // FIXME: why? Shouldn't this just be 0?
SDL_OpenAudio(&audioDevice, &audioActual); // FIXME retval
printf("Actual: freq %d channels %d samples %d\n",
audioActual.freq, audioActual.channels, audioActual.samples);
SDL_PauseAudio(0);
}
void SDLSpeaker::toggle(uint32_t c)
{
pthread_mutex_lock(&togmutex);
/* Figuring out what to do:
*
* The wallclock time we started the app is in startTime.
*
* The wallclock time when the SDL audio buffer will be totally
* drained is in sdlEmptyTime. When that time comes, we want to have
* at least SDLSIZE samples in soundBuf[] - which is currently filled
* to bufIdx samples.
*
* So given the cycle number at which this toggle happened (c), we
* know we need to fill soundBuf[bufIdx..?] with either 0 or 127
* (adjusted for volume). The end of that area that we need to fill is
* based on what time cycle 'c' refers to,
*
* The wallclock time of cycle (c) is calculable from
* timespec_add_cycles(&startTime, c, &outputTime);
*
* And the point at which the SDL buffer will be drained is the same
* as the time at which soundBuf begins. So the difference between
* the two tells us where the end point is.
*
* Then we need to fill soundBuf[bufIdx .. endPoint] with that 0 or 127,
* and set bufIdx = endPoint.
*
* Bonus: if it looks like we're not filling enough buffer, then we
* should tell the emulation layer above to run more cycles in bulk
* to build up more speaker backlog.
*/
// calculate the timespec that refers to the cycle where this
// speaker toggle happened
struct timespec blipTime;
timespec_add_cycles(&startTime, c, &blipTime);
timespec_add_us(&blipTime, ((float)SDLSIZE * (float)1000000)/(float)44100, &blipTime); // it's delayed one SDL buffer naturally, and there's some drift between the start of the CPU and the start of the speaker. :/
// determine how long there will be between the start of the buffer
// and that cycle time. (tsSubtract bounds at 0 and is never
// negative.)
struct timespec timeOffset = tsSubtract(blipTime, sdlEmptyTime);
// Turn that in to a sample index in the soundBuf[] buffer. There are 44100 of them per second,
// so this is straightforward
float newIdx = (float)timeOffset.tv_sec + ((float)timeOffset.tv_nsec / (float)NANOSECONDS_PER_SECOND);
newIdx *= 44100.0;
if (newIdx >= sizeof(soundBuf)) {
// Buffer overrun
printf("ERROR: buffer overrun, dropping data\n");
newIdx = sizeof(soundBuf)-1;
}
// Flip the toggle state
toggleState = !toggleState;
// Fill from bufIdx .. newIdx and set bufIdx to newIdx when done
if (newIdx > bufIdx) {
long count = (long)newIdx - bufIdx;
memset(&soundBuf[bufIdx], toggleState ? 127 : 0, count);
bufIdx = newIdx;
} else {
// Why are we backtracking? This does happen, and it's a bug.
if (newIdx >= 1) {
bufIdx = newIdx-1;
long count = (long)newIdx - bufIdx;
memset(&soundBuf[bufIdx], toggleState ? 127 : 0, count);
bufIdx = newIdx;
} else {
// ... and it's zero?
}
}
pthread_mutex_unlock(&togmutex);
}
// FIXME: make methods
uint16_t dcFilterState = 0;
void ResetDCFilter()
{
dcFilterState = 32768 + 10000;
}
int16_t DCFilter(int16_t in)
{
if (dcFilterState == 0)
return 0;
if (dcFilterState >= 32768) {
dcFilterState--;
return in;
}
return ( (int32_t)in * (int32_t)dcFilterState-- ) / (int32_t)32768;
}
void SDLSpeaker::maintainSpeaker(uint32_t c, uint64_t microseconds)
{
}
void SDLSpeaker::beginMixing()
{
}
void SDLSpeaker::mixOutput(uint8_t v)
{
}