aiie/sdl/sdl-speaker.cpp
2020-12-28 22:57:11 -05:00

234 lines
6.9 KiB
C++

#include "sdl-speaker.h"
#include <pthread.h>
#include <unistd.h>
#include <fcntl.h> // for open()
extern "C"
{
#include <SDL.h>
#include <SDL_thread.h>
};
// What values do we use for logical speaker-high and speaker-low?
#define HIGHVAL ((0x4FFF) >> (15-g_volume))
#define LOWVAL (-((0x4FFF) >> (15-g_volume)))
#include "globals.h"
#define SDLSIZE (2048)
// But we want to keep more than just that, so we can fill it full every time
#define CACHEMULTIPLIER 2
#define WATERLEVEL SDLSIZE
#define AUDIO_SAMPLE_RATE_EXACT 44100
// FIXME: Globals; ick.
static volatile uint32_t bufIdx = 0;
static volatile short soundBuf[CACHEMULTIPLIER*SDLSIZE];
static pthread_mutex_t togmutex = PTHREAD_MUTEX_INITIALIZER;
static volatile uint64_t skippedSamples = 0;
#define SAMPLEBYTES sizeof(short)
volatile uint8_t audioRunning = 0;
volatile int64_t lastFilledTime = 0;
// Debugging by writing a wav file with the sound output...
//#define DEBUG_OUT_WAV
#ifdef DEBUG_OUT_WAV
int outputFD = -1;
#endif
static void audioCallback(void *unused, Uint8 *stream, int len)
{
if (audioRunning==0)
audioRunning=1;
pthread_mutex_lock(&togmutex);
if (g_biosInterrupt) {
// While the BIOS is running, we don't put samples in the audio
// queue.
audioRunning = 0;
memset(stream, 0, SDLSIZE*SAMPLEBYTES);
pthread_mutex_unlock(&togmutex);
return;
}
if (audioRunning==1 && bufIdx >= WATERLEVEL) {
// Fully up and running now; we got a full cache
audioRunning = 2;
} else if (audioRunning==1) {
// waiting for first fill; return an empty buffer.
memset(stream, 0, SDLSIZE*SAMPLEBYTES);
pthread_mutex_unlock(&togmutex);
return;
}
static short lastKnownSample = 0; // saved for when the apple is quiescent
if (bufIdx >= SDLSIZE) { // technically 'len/SAMPLEBYTES' but it should always be constant I think?
memcpy(stream, (void *)soundBuf, SDLSIZE*SAMPLEBYTES);
lastKnownSample = stream[SDLSIZE-1];
if (bufIdx > SDLSIZE) {
// move the remaining data down
memcpy((void *)soundBuf, (void *)&soundBuf[SDLSIZE], (bufIdx - SDLSIZE + 1)*SAMPLEBYTES);
bufIdx -= SDLSIZE;
}
} else {
if (bufIdx) {
// partial buffer exists
memcpy(stream, (void *)soundBuf, bufIdx*SAMPLEBYTES);
// and it's a partial underrun. Track the number of samples we skipped
// so we can keep the audio buffer in sync.
skippedSamples += SDLSIZE-bufIdx;
for (long i=0; i<SDLSIZE-bufIdx; i++) {
stream[bufIdx+i] = lastKnownSample;
}
bufIdx = 0;
} else {
// No big deal - buffer underrun might just mean nothing
// is trying to play audio right now.
skippedSamples += SDLSIZE;
memset(stream, 0, SDLSIZE*SAMPLEBYTES);
// memset(stream, lastKnownSample, SDLSIZE);
// Trend toward DC voltage = 0v
// if (lastKnownSample < 0x7F) lastKnownSample++;
// if (lastKnownSample >= 0x80) lastKnownSample--;
}
}
#ifdef DEBUG_OUT_WAV
if (outputFD == -1) {
outputFD = open("/tmp/out.wav", O_RDWR | O_CREAT | O_TRUNC, 0600);
unsigned char buf[44] = { 'R', 'I', 'F', 'F',
0xff,0xff,0xff,0, // size == 0 for now
'W', 'A', 'V', 'E',
'f', 'm', 't', ' ',
16,0,0,0, // no extensions
1,0, // PCM
1,0, // 1 channel
0x44, 0xAC, 0, 0, // 44100 Hz
0x44, 0xAC, 0, 0, // (sample rate * bits * channels)/8
1,0, // sample size (1 byte here b/c 1 channel @ 8bit)
8,0, // bits per sample
'd', 'a', 't', 'a',
0xff, 0xff, 0xff, 0, // size of data chunk
};
write(outputFD, buf, sizeof(buf));
}
write(outputFD, (void *)(stream), SDLSIZE*SAMPLEBYTES);
#endif
pthread_mutex_unlock(&togmutex);
}
SDLSpeaker::SDLSpeaker()
{
toggleState = false;
mixerValue = 0x80;
pthread_mutex_init(&togmutex, NULL);
}
SDLSpeaker::~SDLSpeaker()
{
}
void SDLSpeaker::begin()
{
SDL_AudioSpec audioDevice;
SDL_AudioSpec audioActual;
SDL_memset(&audioDevice, 0, sizeof(audioDevice));
audioDevice.freq = AUDIO_SAMPLE_RATE_EXACT; // count of 16-bit samples
audioDevice.format = AUDIO_S16;
audioDevice.channels = 1;
audioDevice.samples = SDLSIZE; // SDLSIZE 16-bit samples @ 44100Hz: 4096 is about 1/10th second out of sync
audioDevice.callback = audioCallback;
audioDevice.userdata = NULL;
memset((void *)&soundBuf[0], 0, CACHEMULTIPLIER*SDLSIZE*SAMPLEBYTES);
bufIdx = 0;
skippedSamples = 0;
audioRunning = 0;
SDL_OpenAudio(&audioDevice, &audioActual); // FIXME retval
printf("Actual: freq %d channels %d samples %d\n",
audioActual.freq, audioActual.channels, audioActual.samples);
// FIXME: if any of those don't match the orginal we're gonna be unhappy
SDL_PauseAudio(0);
}
void SDLSpeaker::toggle(int64_t c)
{
pthread_mutex_lock(&togmutex);
int64_t expectedCycleNumber = (float)c * (float)AUDIO_SAMPLE_RATE_EXACT / (float)g_speed;
if (lastFilledTime == 0) {
lastFilledTime = expectedCycleNumber;
}
// This subtracts skippedSamples because those were filled automatically
// by the audioCallback when we had no data.
int64_t audioBufferSamples = expectedCycleNumber - lastFilledTime - skippedSamples;
// If audioBufferSamples < 0, then we need to keep some
// skippedSamples for later; otherwise we can keep moving forward.
if (audioBufferSamples < 0) {
skippedSamples = -audioBufferSamples;
audioBufferSamples = 0;
} else {
// Otherwise we consumed them and can forget about it.
skippedSamples = 0;
}
int32_t newIdx = bufIdx + audioBufferSamples;
if (audioBufferSamples == 0) {
// If the toggle wouldn't result in at least 1 buffer sample change,
// then we'll blatantly skip it here. If this turns out to be
// a problem, we could try setting audioBufferSamples++ and then
// twiddle the lastFilledTime so it looks like it's more in the
// future, but I suspect that would mean missing more future events,
// just like we would have missed this one.
//
// But I think this is probably okay - because something that's
// toggling the speaker fast enough that our 44k audio can't keep
// up with the individual changes is likely to toggle again in a
// moment without significant distortion?
pthread_mutex_unlock(&togmutex);
return;
}
if (newIdx >= sizeof(soundBuf)/SAMPLEBYTES) {
printf("ERROR: buffer overrun: size %lu idx %d\n", sizeof(soundBuf)/SAMPLEBYTES, newIdx);
newIdx = (sizeof(soundBuf)/SAMPLEBYTES)-1;
}
lastFilledTime = expectedCycleNumber;
// 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;
for (long i=0; i<count; i++) {
soundBuf[bufIdx+i] = toggleState ? HIGHVAL : LOWVAL;
}
bufIdx = newIdx;
}
pthread_mutex_unlock(&togmutex);
}
void SDLSpeaker::maintainSpeaker(int64_t c, uint64_t microseconds)
{
}
void SDLSpeaker::beginMixing()
{
}
void SDLSpeaker::mixOutput(uint8_t v)
{
}