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account for missing cycles auto-filled when speaker is quiescent

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This commit is contained in:
Jorj Bauer 2020-07-13 20:28:33 -04:00
parent d78f0dc8cf
commit a67cc53bcd
1 changed files with 21 additions and 26 deletions
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47
sdl/sdl-speaker.cpp
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@ -15,8 +15,6 @@ extern "C"
#include "globals.h"
#include "timeutil.h"
#define SDLSIZE (4096)
// But we want to keep more than just that, so we can fill it full every time
#define CACHEMULTIPLIER 2
@ -25,14 +23,10 @@ extern "C"
static volatile uint32_t bufIdx = 0;
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)
static volatile uint32_t skippedSamples = 0;
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
@ -59,16 +53,10 @@ static void audioCallback(void *unused, Uint8 *stream, int len)
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);
sdlEmptyTime = tsSubtract(sdlEmptyTime, sdlStartTime);
static uint8_t lastKnownSample = 0; // saved for when the apple is quiescent
if (bufIdx >= len) {
@ -84,12 +72,15 @@ static void audioCallback(void *unused, Uint8 *stream, int len)
if (bufIdx) {
// partial buffer exists
memcpy(stream, (void *)soundBuf, bufIdx);
// and it's a partial underrun
// and it's a partial underrun. Track the number of samples we skipped
// so we can keep the audio buffer in sync.
skippedSamples += len-bufIdx;
memset(&stream[bufIdx], lastKnownSample, len-bufIdx);
bufIdx = 0;
} else {
// No big deal - buffer underrun might just mean nothing
// is trying to play audio right now.
skippedSamples += len;
memset(stream, 0x80, len);
// memset(stream, lastKnownSample, len);
@ -131,8 +122,6 @@ SDLSpeaker::SDLSpeaker()
pthread_mutex_init(&togmutex, NULL);
_init_darwin_shim();
lastCycleCount = 0;
lastSampleCount = 0;
}
@ -143,10 +132,6 @@ 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));
@ -176,9 +161,21 @@ void SDLSpeaker::toggle(uint32_t c)
if (lastFilledTime == 0) {
lastFilledTime = expectedCycleNumber;
}
uint32_t audioBufferSamples = expectedCycleNumber - lastFilledTime;
uint32_t newIdx = bufIdx + audioBufferSamples;
// This subtracts skippedSamples because those were filled automatically
// by the audioCallback when we had no data.
int32_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
@ -195,10 +192,8 @@ void SDLSpeaker::toggle(uint32_t c)
return;
}
if (newIdx >= sizeof(soundBuf)) {
printf("Buffer overrun: size %d idx %d\n", sizeof(soundBuf), newIdx);
// printf("ERROR: buffer overrun, dropping data; need to increase buffer\n");
printf("ERROR: buffer overrun: size %lu idx %d\n", sizeof(soundBuf), newIdx);
newIdx = sizeof(soundBuf)-1;
}
lastFilledTime = expectedCycleNumber;