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Audio improvements

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This commit is contained in:
Jorj Bauer 2020-07-13 19:01:41 -04:00
parent 1062cec90c
commit d78f0dc8cf
1 changed files with 97 additions and 93 deletions
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190
sdl/sdl-speaker.cpp
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@ -1,6 +1,7 @@
#include "sdl-speaker.h"
#include <pthread.h>
#include <unistd.h>
#include <fcntl.h> // for open()
extern "C"
{
@ -8,31 +9,61 @@ extern "C"
#include <SDL_thread.h>
};
// What values do we use for logical speaker-high and speaker-low?
#define HIGHVAL 0xC0
#define LOWVAL 0x40
#include "globals.h"
#include "timeutil.h"
// FIXME: 4096 is the right value here, I'm just debugging
#define SDLSIZE (4096)
// But we want to keep more than just that, so we can fill it full every time
#define CACHEMULTIPLIER 2
// FIXME: Globals; ick.
static volatile uint32_t bufIdx = 0;
static uint8_t soundBuf[44100];
static volatile uint8_t soundBuf[CACHEMULTIPLIER*SDLSIZE];
static pthread_mutex_t togmutex = PTHREAD_MUTEX_INITIALIZER;
static struct timespec sdlEmptyTime, sdlStartTime;
extern struct timespec startTime; // defined in aiie (main)
volatile uint8_t audioRunning = 0;
// How many cpu cycles do we lag "real time"? (Enough to give us a
// solid audio buffer fill...)
#define PLAYBACK_LAG ((SDLSIZE/44100)*1023000)
// 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, 0x80, len);
pthread_mutex_unlock(&togmutex);
return;
}
if (audioRunning==1 && bufIdx >= len) {
// Fully up and running now; we got a full cache
audioRunning = 2;
} else if (audioRunning==1) {
// waiting for first fill; return an empty buffer.
printf("pre\n");
memset(stream, 0x80, len);
return;
}
// calculate when the buffer will be empty again
do_gettime(&sdlEmptyTime);
timespec_add_us(&sdlEmptyTime, ((float)len * (float)1000000)/(float)44100, &sdlEmptyTime);
@ -41,32 +72,57 @@ static void audioCallback(void *unused, Uint8 *stream, int len)
static uint8_t lastKnownSample = 0; // saved for when the apple is quiescent
if (bufIdx >= len) {
memcpy(stream, soundBuf, len);
memcpy(stream, (void *)soundBuf, len);
lastKnownSample = stream[len-1];
if (bufIdx > len) {
// move the remaining data down
memcpy(soundBuf, &soundBuf[len], bufIdx - len + 1);
memcpy((void *)soundBuf, (void *)&soundBuf[len], bufIdx - len + 1);
bufIdx -= len;
}
} else {
if (bufIdx) {
// partial buffer exists
memcpy(stream, soundBuf, bufIdx);
memcpy(stream, (void *)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);
// No big deal - buffer underrun might just mean nothing
// is trying to play audio right now.
memset(stream, 0x80, len);
// memset(stream, lastKnownSample, len);
// Trend toward DC voltage = 0v
// if (lastKnownSample < 0x7F) lastKnownSample++;
// if (lastKnownSample >= 0x80) lastKnownSample--;
}
}
pthread_mutex_unlock(&togmutex);
#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));
}
void ResetDCFilter(); // FIXME: remove
write(outputFD, (void *)(stream), len);
#endif
pthread_mutex_unlock(&togmutex);
}
SDLSpeaker::SDLSpeaker()
{
@ -77,8 +133,6 @@ SDLSpeaker::SDLSpeaker()
_init_darwin_shim();
ResetDCFilter();
lastCycleCount = 0;
lastSampleCount = 0;
}
@ -103,115 +157,65 @@ void SDLSpeaker::begin()
audioDevice.callback = audioCallback;
audioDevice.userdata = NULL;
memset(&soundBuf[0], 0, SDLSIZE);
bufIdx = SDLSIZE/2; // FIXME: why? Shouldn't this just be 0?
memset((void *)&soundBuf[0], 0, CACHEMULTIPLIER*SDLSIZE);
bufIdx = 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);
}
uint32_t lastFilledTime = 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.
*/
uint32_t expectedCycleNumber = (float)c * (float)44100 / (float)g_speed;
if (lastFilledTime == 0) {
lastFilledTime = expectedCycleNumber;
}
uint32_t audioBufferSamples = expectedCycleNumber - lastFilledTime;
uint32_t newIdx = bufIdx + audioBufferSamples;
// 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. :/
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;
}
// 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");
printf("Buffer overrun: size %d idx %d\n", sizeof(soundBuf), newIdx);
// printf("ERROR: buffer overrun, dropping data; need to increase buffer\n");
newIdx = sizeof(soundBuf)-1;
}
lastFilledTime = expectedCycleNumber;
// Flip the toggle state
toggleState = !toggleState;
// Fill from bufIdx .. newIdx and set bufIdx to newIdx when done
// 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);
memset((void *)&soundBuf[bufIdx], toggleState ? HIGHVAL : LOWVAL, 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)
{
}