#define SAMPLE_RATE (44100.0)
#define SAMPLES_PER_FRAME (SAMPLE_RATE / 60.0)
-#define CYCLES_PER_SAMPLE ((1024000.0 / 60.0) / (SAMPLES_PER_FRAME))
-#define SOUND_BUFFER_SIZE 8192
-#define AMPLITUDE (32) // -32 - +32 seems to be plenty loud!
+#define CYCLES_PER_SAMPLE (1024000.0 / SAMPLE_RATE)
+#define SOUND_BUFFER_SIZE (8192)
+#define AMPLITUDE (32) // -32 - +32 seems to be plenty loud!
// Global variables
static SDL_AudioSpec desired;
static bool soundInitialized = false;
-static bool speakerState;
+static bool speakerState = false;
static uint8 soundBuffer[SOUND_BUFFER_SIZE];
static uint32 soundBufferPos;
static uint32 sampleBase;
static SDL_cond * conditional = NULL;
static SDL_mutex * mutex = NULL;
+static SDL_mutex * mutex2 = NULL;
// Private function prototypes
conditional = SDL_CreateCond();
mutex = SDL_CreateMutex();
+ mutex2 = SDL_CreateMutex();// Let's try real signalling...
SDL_mutexP(mutex); // Must lock the mutex for the cond to work properly...
soundBufferPos = 0;
sampleBase = 0;
SDL_CloseAudio();
SDL_DestroyCond(conditional);
SDL_DestroyMutex(mutex);
+ SDL_DestroyMutex(mutex2);
WriteLog("Sound: Done.\n");
}
}
// (But, then again, if the sound hasn't been toggled for a while, then this
// makes perfect sense as the buffer won't have been filled at all!)
+ // Let's try using a mutex for shared resource consumption...
+ SDL_mutexP(mutex2);
+
if (soundBufferPos < (uint32)length) // The sound buffer is starved...
{
//printf("Sound buffer starved!\n");
soundBufferPos = 0; // Reset soundBufferPos to start of buffer...
sampleBase = 0; // & sampleBase...
//Ick. This should never happen!
-SDL_CondSignal(conditional); // Wake up any threads waiting for the buffer to drain...
- return; // & bail!
+//Actually, this probably happens a lot. (?)
+// SDL_CondSignal(conditional); // Wake up any threads waiting for the buffer to drain...
+// return; // & bail!
}
+ else
+ {
+ // Fill sound buffer with frame buffered sound
+ memcpy(buffer, soundBuffer, length);
+ soundBufferPos -= length;
+ sampleBase -= length;
- memcpy(buffer, soundBuffer, length); // Fill sound buffer with frame buffered sound
- soundBufferPos -= length;
- sampleBase -= length;
-
-// if (soundBufferPos > 0)
-// memcpy(soundBuffer, soundBuffer + length, soundBufferPos); // Move current buffer down to start
-// memcpy(soundBuffer, soundBuffer + length, length);
- // Move current buffer down to start
- for(uint32 i=0; i<soundBufferPos; i++)
- soundBuffer[i] = soundBuffer[length + i];
+ // Move current buffer down to start
+ for(uint32 i=0; i<soundBufferPos; i++)
+ soundBuffer[i] = soundBuffer[length + i];
+ }
-// lastValue = buffer[length - 1];
- SDL_CondSignal(conditional); // Wake up any threads waiting for the buffer to drain...
+ // Free the mutex...
+ SDL_mutexV(mutex2);
+ // Wake up any threads waiting for the buffer to drain...
+// SDL_CondSignal(conditional);
}
// Need some interface functions here to take care of flipping the
// Need the last frame position in order to calculate correctly...
// (or do we?)
- SDL_LockAudio();
+// SDL_LockAudio();
+ SDL_mutexP(mutex2);
uint32 currentPos = sampleBase + (uint32)((double)time / CYCLES_PER_SAMPLE);
if (currentPos > SOUND_BUFFER_SIZE - 1)
Seems like it's OK now that I've fixed the buffer-less-than-length bug...
*/
- SDL_UnlockAudio();
- SDL_CondWait(conditional, mutex);
- SDL_LockAudio();
- currentPos = sampleBase + (uint32)((double)time / 23.2199);
+// SDL_UnlockAudio();
+// SDL_CondWait(conditional, mutex);
+// SDL_LockAudio();
+ currentPos = sampleBase + (uint32)((double)time / CYCLES_PER_SAMPLE);
#if 0
WriteLog("--> after spinlock (sampleBase=%u)...\n", sampleBase);
#endif
while (soundBufferPos < currentPos)
soundBuffer[soundBufferPos++] = (uint8)sample;
+ // This is done *after* in case the buffer had a long dead spot (I think...)
speakerState = !speakerState;
- SDL_UnlockAudio();
+ SDL_mutexV(mutex2);
+// SDL_UnlockAudio();
}
-void HandleSoundAtFrameEdge(void)
+void AddToSoundTimeBase(uint32 cycles)
{
if (!soundInitialized)
return;
- SDL_LockAudio();
- sampleBase += SAMPLES_PER_FRAME;
- SDL_UnlockAudio();
+// SDL_LockAudio();
+ SDL_mutexP(mutex2);
+ sampleBase += (uint32)((double)cycles / CYCLES_PER_SAMPLE);
+ SDL_mutexV(mutex2);
+// SDL_UnlockAudio();
}
/*
+HOW IT WORKS
+
+the main thread adds the amount of cpu time elapsed to samplebase. togglespeaker uses
+samplebase + current cpu time to find appropriate spot in buffer. it then fills the
+buffer up to the current time with the old toggle value before flipping it. the sound
+irq takes what it needs from the sound buffer and then adjusts both the buffer and
+samplebase back the appropriate amount.
+
+
A better way might be as follows:
-Keep timestamp array of speaker toggle times. In the sound routine, unpack as many as will fit
-into the given buffer and keep going. Have the toggle function check to see if the buffer is full,
-and if it is, way for a signal from the interrupt that there's room for more. Can keep a circular
-buffer. Also, would need a timestamp buffer on the order of 2096 samples *in theory* could toggle
-each sample
+Keep timestamp array of speaker toggle times. In the sound routine, unpack as many as will
+fit into the given buffer and keep going. Have the toggle function check to see if the
+buffer is full, and if it is, way for a signal from the interrupt that there's room for
+more. Can keep a circular buffer. Also, would need a timestamp buffer on the order of 2096
+samples *in theory* could toggle each sample
-Instead of a timestamp, just keep a delta. That way, don't need to deal with wrapping and all that
-(though the timestamp could wrap--need to check into that)
+Instead of a timestamp, just keep a delta. That way, don't need to deal with wrapping and
+all that (though the timestamp could wrap--need to check into that)
Need to consider corner cases where a sound IRQ happens but no speaker toggle happened.
+If (delta > SAMPLES_PER_FRAME) then
+
+Here's the relevant cases:
+
+delta < SAMPLES_PER_FRAME -> Change happened within this time frame, so change buffer
+frame came and went, no change -> fill buffer with last value
+How to detect: Have bool bufferWasTouched = true when ToggleSpeaker() is called.
+Clear bufferWasTouched each frame.
+
+Two major cases here:
+
+ o Buffer is touched on current frame
+ o Buffer is untouched on current frame
+
+In the first case, it doesn't matter too much if the previous frame was touched or not,
+we don't really care except in finding the correct spot in the buffer to put our change
+in. In the second case, we need to tell the IRQ that nothing happened and to continue
+to output the same value.
+
+SO: How to synchronize the regular frame buffer with the IRQ buffer?
+
+What happens:
+ Sound IRQ --> Every 1024 sample period (@ 44.1 KHz = 0.0232s)
+ Emulation --> Render a frame --> 1/60 sec --> 735 samples
+ --> sound buffer is filled
+
+Since the emulation is faster than the SIRQ the sound buffer should fill up
+prior to dumping it to the sound card.
+
+Problem is this: If silence happens for a long time then ToggleSpeaker is never
+called and the sound buffer has stale data; at least until soundBufferPos goes to
+zero and stays there...
+
+BUT this should be handled correctly by toggling the speaker value *after* filling
+the sound buffer...
+
+Still getting random clicks when running...
+(This may be due to the lock/unlock sound happening in ToggleSpeaker()...)
*/
+
+
+
+
projects / apple2 / blobdiff