peakmeter.cpp

#include "peakmeter.h"

void AudioPeakHold::update(void)
{
	audio_block_t *block;
	const int16_t *p, *end;

	block = receiveReadOnly();
	if (!block) {
		return;
	}
	
	// shift the old blockPeak
	for(int i = PEAK_HOLD_BLOCKS - 1; i > 0; i--){
		blockPeak[i] = blockPeak[i-1];
    blockSqAccum[i] = blockSqAccum[i-1];
	}
	
	uint16_t thisBlockPeak = 0;

  // calculate peak
	p = block->data;
	end = p + AUDIO_BLOCK_SAMPLES;
	do {
		int32_t d=*p++;
    d = abs(d);
		// TODO: can we speed this up with SSUB16 and SEL
		// http://www.m4-unleashed.com/parallel-comparison/
		if(d > thisBlockPeak){
			thisBlockPeak = d;
		}
	} while (p < end);

  // calculate sum of squared samples
  p = block->data;
  end = p + AUDIO_BLOCK_SAMPLES;
  int64_t sum = 0;
  do {
    int32_t n = *p++;
    sum += n * n;
  } while (p < end);
  blockSqAccum[0] = sum;

	blockPeak[0] = thisBlockPeak;
	
	peak = 0;
  meanSq = 0;
	for(int i = 0; i < PEAK_HOLD_BLOCKS; i++){
		if(blockPeak[i] > peak){
			peak = blockPeak[i];
		}
    meanSq += blockSqAccum[i];
  }
  meanSq /= AUDIO_BLOCK_SAMPLES * PEAK_HOLD_BLOCKS;
	
	release(block);
}