From f5e7aa11f9a601e400dbe859ccafc94c275cb885 Mon Sep 17 00:00:00 2001
From: Tim Mayberry <mojofunk@gmail.com>
Date: Fri, 11 Sep 2015 23:07:01 +1000
Subject: [PATCH] Use same algorithm as CA and ALSA backends in
 DSPLoadCalculation

Stop using an averaging of the values until we can establish whether it is
really necessary.
---
 libs/ardour/ardour/dsp_load_calculator.h | 18 +-------
 libs/ardour/dsp_load_calculator.cc       | 54 +++---------------------
 2 files changed, 8 insertions(+), 64 deletions(-)

diff --git a/libs/ardour/ardour/dsp_load_calculator.h b/libs/ardour/ardour/dsp_load_calculator.h
index f3c5fea227..42386e2cb0 100644
--- a/libs/ardour/ardour/dsp_load_calculator.h
+++ b/libs/ardour/ardour/dsp_load_calculator.h
@@ -23,8 +23,6 @@
 #include <cassert>
 #include <algorithm>
 
-#include <pbd/ringbuffer.h>
-
 #include "ardour/libardour_visibility.h"
 
 namespace ARDOUR {
@@ -36,8 +34,6 @@ public:
 	    , m_start_timestamp_us(0)
 	    , m_stop_timestamp_us(0)
 	    , m_dsp_load(0)
-	    , m_value_history (max_value_history())
-	    , m_num_values(0)
 	{
 
 	}
@@ -45,17 +41,8 @@ public:
 	void set_max_time_us(uint64_t max_time_us) {
 		assert(max_time_us != 0);
 		m_max_time_us = max_time_us;
-
-		// Use average of last 1/4 second of values so responsiveness
-		// remains consistent independent of max time
-		uint32_t max_dsp_samples_per_qtr_second = (250000 / m_max_time_us);
-		m_num_values =
-		    std::min(max_value_history() - 1, max_dsp_samples_per_qtr_second);
-
-		m_value_history.reset();
 	}
 
-
 	int64_t get_max_time_us() const { return m_max_time_us; }
 
 	void set_start_timestamp_us(int64_t start_timestamp_us)
@@ -85,9 +72,8 @@ public:
 		}
 		return m_dsp_load;
 	}
-private: // methods
-	static uint32_t max_value_history () { return 16; }
 
+private: // methods
 	int64_t max_timer_error () { return 4 * m_max_time_us; }
 
 private: // data
@@ -95,8 +81,6 @@ private: // data
 	int64_t m_start_timestamp_us;
 	int64_t m_stop_timestamp_us;
 	float m_dsp_load;
-	RingBuffer<float> m_value_history;
-	uint32_t m_num_values;
 };
 
 } // namespace ARDOUR
diff --git a/libs/ardour/dsp_load_calculator.cc b/libs/ardour/dsp_load_calculator.cc
index 6b8e2b70e7..789d3704f4 100644
--- a/libs/ardour/dsp_load_calculator.cc
+++ b/libs/ardour/dsp_load_calculator.cc
@@ -23,10 +23,6 @@ namespace ARDOUR {
 void
 DSPLoadCalculator::set_stop_timestamp_us(int64_t stop_timestamp_us)
 {
-	// We could only bother with calculations if a certain amount of time
-	// has passed, or the Raw DSP value is > X% different than last calc
-	// which would mean consistent overhead for small values of m_max_time_us
-
 	m_stop_timestamp_us = stop_timestamp_us;
 
 	/* querying the performance counter can fail occasionally (-1).
@@ -41,52 +37,16 @@ DSPLoadCalculator::set_stop_timestamp_us(int64_t stop_timestamp_us)
 		   return;
 	}
 
-	float load = 0;
-
 	if (elapsed_time_us() > m_max_time_us) {
-		load = 1.0f;
+		m_dsp_load = 1.0f;
 	} else {
-		load = elapsed_time_us() / (float)m_max_time_us;
-	}
-
-	assert(m_value_history.write_space() >= 1);
-
-	// push raw load value onto history
-	m_value_history.write(&load, 1);
-
-	// if load is under 80% use an average of past values
-	if (elapsed_time_us() < ((m_max_time_us * 80) / 100)) {
-
-		RingBuffer<float>::rw_vector vec;
-		m_value_history.get_read_vector(&vec);
-		uint32_t values_read = 0;
-		float dsp_accumulator = 0.0f;
-
-		// iterate through the read vectors accumulating the dsp load
-		for (unsigned int i = 0; i < vec.len[0]; ++i) {
-			dsp_accumulator += vec.buf[0][i];
-			values_read++;
+		const float load = elapsed_time_us() / (float)m_max_time_us;
+		if (load > m_dsp_load) {
+			m_dsp_load = load;
+		} else {
+			const float alpha = 0.2f * (m_max_time_us * 1e-6f);
+			m_dsp_load = m_dsp_load + alpha * (load - m_dsp_load) + 1e-12;
 		}
-
-		for (unsigned int i = 0; i < vec.len[1]; ++i) {
-			dsp_accumulator += vec.buf[1][i];
-			values_read++;
-		}
-
-		load = dsp_accumulator / (float)values_read;
-
-		const float alpha = 0.2f * (m_max_time_us * 1e-6f);
-		m_dsp_load = m_dsp_load + alpha * (load - m_dsp_load) + 1e-12;
-
-	} else {
-		// Use raw load value otherwise 100% may never be indicated because of
-		// averaging/LPF etc
-		m_dsp_load = load;
-	}
-
-	if (m_value_history.read_space() >= m_num_values) {
-		// "remove" the oldest value
-		m_value_history.increment_read_idx(1);
 	}
 }