From: Joel Holdsworth <redacted>
Date: Sat, 16 Mar 2013 10:11:50 +0000 (+0000)
Subject: Added code to construct analog envelope levels
X-Git-Tag: pulseview-0.1.0~75
X-Git-Url: https://sigrok.org/gitweb/?p=pulseview.git;a=commitdiff_plain;h=fda5b6e0e0ebbe55f3d173051b8800293f87cd09

Added code to construct analog envelope levels
---

diff --git a/pv/data/analogsnapshot.cpp b/pv/data/analogsnapshot.cpp
index 1658a04c..c052782e 100644
--- a/pv/data/analogsnapshot.cpp
+++ b/pv/data/analogsnapshot.cpp
@@ -25,6 +25,8 @@
 #include <stdlib.h>
 #include <math.h>
 
+#include <algorithm>
+
 #include <boost/foreach.hpp>
 
 #include "analogsnapshot.h"
@@ -35,18 +37,35 @@ using namespace std;
 namespace pv {
 namespace data {
 
+const int AnalogSnapshot::EnvelopeScalePower = 4;
+const int AnalogSnapshot::EnvelopeScaleFactor = 1 << EnvelopeScalePower;
+const float AnalogSnapshot::LogEnvelopeScaleFactor =
+	logf(EnvelopeScaleFactor);
+const uint64_t AnalogSnapshot::EnvelopeDataUnit = 64*1024;	// bytes
+
 AnalogSnapshot::AnalogSnapshot(const sr_datafeed_analog &analog) :
 	Snapshot(sizeof(float))
 {
 	lock_guard<recursive_mutex> lock(_mutex);
+	memset(_envelope_levels, 0, sizeof(_envelope_levels));
 	append_payload(analog);
 }
 
+AnalogSnapshot::~AnalogSnapshot()
+{
+	lock_guard<recursive_mutex> lock(_mutex);
+	BOOST_FOREACH(Envelope &e, _envelope_levels)
+		free(e.samples);
+}
+
 void AnalogSnapshot::append_payload(
 	const sr_datafeed_analog &analog)
 {
 	lock_guard<recursive_mutex> lock(_mutex);
 	append_data(analog.data, analog.num_samples);
+
+	// Generate the first mip-map from the data
+	append_payload_to_envelope_levels();
 }
 
 const float* AnalogSnapshot::get_samples(
@@ -66,5 +85,89 @@ const float* AnalogSnapshot::get_samples(
 	return data;
 }
 
+void AnalogSnapshot::reallocate_envelope(Envelope &e)
+{
+	const uint64_t new_data_length = ((e.length + EnvelopeDataUnit - 1) /
+		EnvelopeDataUnit) * EnvelopeDataUnit;
+	if (new_data_length > e.data_length)
+	{
+		e.data_length = new_data_length;
+		e.samples = (EnvelopeSample*)realloc(e.samples,
+			new_data_length * sizeof(EnvelopeSample));
+	}
+}
+
+void AnalogSnapshot::append_payload_to_envelope_levels()
+{
+	Envelope &e0 = _envelope_levels[0];
+	uint64_t prev_length;
+	EnvelopeSample *dest_ptr;
+
+	// Expand the data buffer to fit the new samples
+	prev_length = e0.length;
+	e0.length = _sample_count / EnvelopeScaleFactor;
+
+	// Break off if there are no new samples to compute
+	if (e0.length == prev_length)
+		return;
+
+	reallocate_envelope(e0);
+
+	dest_ptr = e0.samples + prev_length;
+
+	// Iterate through the samples to populate the first level mipmap
+	const float *const end_src_ptr = (float*)_data +
+		e0.length * EnvelopeScaleFactor;
+	for (const float *src_ptr = (float*)_data +
+		prev_length * EnvelopeScaleFactor;
+		src_ptr < end_src_ptr; src_ptr += EnvelopeScaleFactor)
+	{
+		const EnvelopeSample sub_sample = {
+			*min_element(src_ptr, src_ptr + EnvelopeScaleFactor),
+			*max_element(src_ptr, src_ptr + EnvelopeScaleFactor),
+		};
+
+		*dest_ptr++ = sub_sample;
+	}
+
+	// Compute higher level mipmaps
+	for (unsigned int level = 1; level < ScaleStepCount; level++)
+	{
+		Envelope &e = _envelope_levels[level];
+		const Envelope &el = _envelope_levels[level-1];
+
+		// Expand the data buffer to fit the new samples
+		prev_length = e.length;
+		e.length = el.length / EnvelopeScaleFactor;
+
+		// Break off if there are no more samples to computed
+		if (e.length == prev_length)
+			break;
+
+		reallocate_envelope(e);
+
+		// Subsample the level lower level
+		const EnvelopeSample *src_ptr =
+			el.samples + prev_length * EnvelopeScaleFactor;
+		const EnvelopeSample *const end_dest_ptr = e.samples + e.length;
+		for (dest_ptr = e.samples + prev_length;
+			dest_ptr < end_dest_ptr; dest_ptr++)
+		{
+			const EnvelopeSample *const end_src_ptr =
+				src_ptr + EnvelopeScaleFactor;
+
+			EnvelopeSample sub_sample = *src_ptr++;
+			while (src_ptr < end_src_ptr)
+			{
+				sub_sample.min = min(sub_sample.min, src_ptr->min);
+				sub_sample.max = max(sub_sample.max, src_ptr->max);
+				src_ptr++;
+			}
+
+			*dest_ptr = sub_sample;
+		}
+	}
+}
+
 } // namespace data
 } // namespace pv
diff --git a/pv/data/analogsnapshot.h b/pv/data/analogsnapshot.h
index a4539184..8eec2797 100644
--- a/pv/data/analogsnapshot.h
+++ b/pv/data/analogsnapshot.h
@@ -31,15 +31,44 @@ namespace data {
 
 class AnalogSnapshot : public Snapshot
 {
+private:
+	struct EnvelopeSample
+	{
+		float min;
+		float max;
+	};
+
+	struct Envelope
+	{
+		uint64_t length;
+		uint64_t data_length;
+		EnvelopeSample *samples;
+	};
+
+private:
+	static const unsigned int ScaleStepCount = 10;
+	static const int EnvelopeScalePower;
+	static const int EnvelopeScaleFactor;
+	static const float LogEnvelopeScaleFactor;
+	static const uint64_t EnvelopeDataUnit;
+
 public:
 	AnalogSnapshot(const sr_datafeed_analog &analog);
 
+	virtual ~AnalogSnapshot();
+
 	void append_payload(const sr_datafeed_analog &analog);
 
 	const float* get_samples(int64_t start_sample,
 		int64_t end_sample) const;
-};
 
+private:
+	void reallocate_envelope(Envelope &l);
+
+	void append_payload_to_envelope_levels();
+
+private:
+	struct Envelope _envelope_levels[ScaleStepCount];
 } // namespace data
 } // namespace pv