Fix numerical overflow in audio CPU usage measurement

https://forum.pjrc.com/threads/61412

teensy4/AudioStream.cpp

@@ -321,13 +321,13 @@ void software_isr(void) // AudioStream::update_all()
 			p->update();
 			// TODO: traverse inputQueueArray and release
 			// any input blocks that weren't consumed?
-			cycles = (ARM_DWT_CYCCNT - cycles) >> 4;
+			cycles = (ARM_DWT_CYCCNT - cycles) >> 6;
 			p->cpu_cycles = cycles;
 			if (cycles > p->cpu_cycles_max) p->cpu_cycles_max = cycles;
 		}
 	}
 	//digitalWriteFast(2, LOW);
-	totalcycles = (ARM_DWT_CYCCNT - totalcycles) >> 4;;
+	totalcycles = (ARM_DWT_CYCCNT - totalcycles) >> 6;
 	AudioStream::cpu_cycles_total = totalcycles;
 	if (totalcycles > AudioStream::cpu_cycles_total_max)
 		AudioStream::cpu_cycles_total_max = totalcycles;

teensy4/AudioStream.h

@@ -105,7 +105,7 @@ protected:
 	AudioStream::initialize_memory(data, num); \
 })
 
-#define CYCLE_COUNTER_APPROX_PERCENT(n) (((n) + (F_CPU_ACTUAL / 32 / AUDIO_SAMPLE_RATE * AUDIO_BLOCK_SAMPLES / 100)) / (F_CPU_ACTUAL / 16 / AUDIO_SAMPLE_RATE * AUDIO_BLOCK_SAMPLES / 100))
+#define CYCLE_COUNTER_APPROX_PERCENT(n) (((n) + (F_CPU_ACTUAL / 128 / AUDIO_SAMPLE_RATE * AUDIO_BLOCK_SAMPLES / 100)) / (F_CPU_ACTUAL / 64 / AUDIO_SAMPLE_RATE * AUDIO_BLOCK_SAMPLES / 100))
 
 #define AudioProcessorUsage() (CYCLE_COUNTER_APPROX_PERCENT(AudioStream::cpu_cycles_total))
 #define AudioProcessorUsageMax() (CYCLE_COUNTER_APPROX_PERCENT(AudioStream::cpu_cycles_total_max))