inspectrum/spectrogram.cpp

#include "spectrogram.h"

#include <QDebug>
#include <QElapsedTimer>
#include <QPainter>
#include <QPaintEvent>
#include <QRect>

#include <cstdlib>


Spectrogram::Spectrogram()
{
	sampleRate = 8000000;
	setFFTSize(1024);
	zoomLevel = 0;
	powerMax = 0.0f;
	powerMin = -50.0f;

	for (int i = 0; i < 256; i++) {
		float p = (float)i / 256;
		colormap[i] = QColor::fromHsvF(p * 0.83f, 1.0, 1.0 - p).rgba();
	}
}

Spectrogram::~Spectrogram()
{
	delete fft;
	delete inputSource;
}

QSize Spectrogram::sizeHint() const {
	return QSize(1024, 2048);
}

void Spectrogram::openFile(QString fileName)
{
	if (fileName != nullptr) {
		try {
			InputSource *newFile = new InputSource(fileName.toUtf8().constData());
			delete inputSource;
			inputSource = newFile;
			resize(fftSize, getHeight());
		} catch (std::runtime_error e) {
			// TODO: display error
		}
	}
}

template <class T> const T& clamp (const T& value, const T& min, const T& max) {
    return std::min(max, std::max(min, value));
}

void Spectrogram::paintEvent(QPaintEvent *event)
{
	QElapsedTimer timer;
	timer.start();

	QRect rect = event->rect();
	QPainter painter(this);
	painter.fillRect(rect, Qt::black);

	if (inputSource != nullptr) {
		int height = rect.height();
		int y = rect.y();

		QImage image(fftSize, height, QImage::Format_RGB32);

		while (height > 0) {
			int tileOffset = y % linesPerTile(); // To handle drawing a partial first tile
			int drawHeight = std::min(linesPerTile() - tileOffset, height); // Draw rest of first tile, full tile, or partial final tile
			off_t tileId = lineToSample(y - tileOffset);
			QPixmap *tile = getPixmapTile(tileId);
			painter.drawPixmap(QRect(0, y, fftSize, drawHeight), *tile, QRect(0, tileOffset, fftSize, drawHeight));
			y += drawHeight;
			height -= drawHeight;
		}

		paintTimeAxis(&painter, rect);
	}

	qDebug() << "Paint: " << timer.elapsed() << "ms";
}

QPixmap* Spectrogram::getPixmapTile(off_t tile)
{
	QPixmap *obj = pixmapCache.object(TileCacheKey(fftSize, zoomLevel, tile));
	if (obj != 0)
		return obj;

	float *fftTile = getFFTTile(tile);
	obj = new QPixmap(fftSize, linesPerTile());
	QImage image(fftSize, linesPerTile(), QImage::Format_RGB32);
	for (int y = 0; y < linesPerTile(); y++) {
		float *line = &fftTile[y * fftSize];
		for (int x = 0; x < fftSize; x++) {
			float powerRange = std::abs(int(powerMin - powerMax));
			float normPower = (line[x] - powerMax) * -1.0f / powerRange;
			normPower = clamp(normPower, 0.0f, 1.0f);

			image.setPixel(x, y, colormap[(uint8_t)(normPower * (256 - 1))]);
		}
	}
	obj->convertFromImage(image);
	pixmapCache.insert(TileCacheKey(fftSize, zoomLevel, tile), obj);
	return obj;
}

float* Spectrogram::getFFTTile(off_t tile)
{
	float *obj = fftCache.object(TileCacheKey(fftSize, zoomLevel, tile));
	if (obj != 0)
		return obj;

	float *dest = new float[tileSize];
	float *ptr = dest;
	off_t sample = tile;
	while ((ptr - dest) < tileSize) {
		getLine(ptr, sample);
		sample += getStride();
		ptr += fftSize;
	}
	fftCache.insert(TileCacheKey(fftSize, zoomLevel, tile), dest);
	return dest;
}

void Spectrogram::getLine(float *dest, off_t sample)
{
	if (inputSource && fft) {
		fftwf_complex buffer[fftSize];
		inputSource->getSamples(buffer, sample, fftSize);

		for (int i = 0; i < fftSize; i++) {
			buffer[i][0] *= window[i];
			buffer[i][1] *= window[i];
		}

		fft->process(buffer, buffer);
		for (int i = 0; i < fftSize; i++) {
			int k = (i + fftSize / 2) % fftSize;
			float re = buffer[k][0];
			float im = buffer[k][1];
			float mag = sqrt(re * re + im * im) / fftSize;
			float magdb = 10 * log2(mag) / log2(10);
			*dest = magdb;
			dest++;
		}
	}
}

void Spectrogram::paintTimeAxis(QPainter *painter, QRect rect)
{
	// Round up for firstLine and round each to nearest linesPerGraduation
	int firstLine = ((rect.y() + linesPerGraduation - 1) / linesPerGraduation) * linesPerGraduation;
	int lastLine = ((rect.y() + rect.height()) / linesPerGraduation) * linesPerGraduation;

	painter->save();
	QPen pen(Qt::white, 1, Qt::SolidLine);
	painter->setPen(pen);
	QFontMetrics fm(painter->font());
	int textOffset = fm.ascent() / 2 - 1;
	for (int line = firstLine; line <= lastLine; line += linesPerGraduation) {
		painter->drawLine(0, line, 10, line);
		painter->drawText(12, line + textOffset, sampleToTime(lineToSample(line)));
	}
	painter->restore();
}

void Spectrogram::setSampleRate(int rate)
{
	sampleRate = rate;
	update();
}

void Spectrogram::setFFTSize(int size)
{
	fftSize = size;
	delete fft;
	fft = new FFT(fftSize);

	window.reset(new float[fftSize]);
	for (int i = 0; i < fftSize; i++) {
		window[i] = 0.5f * (1.0f - cos(Tau * i / (fftSize - 1)));
	}

	resize(fftSize, getHeight());
}

void Spectrogram::setPowerMax(int power)
{
	powerMax = power;
	pixmapCache.clear();
	update();
}

void Spectrogram::setPowerMin(int power)
{
	powerMin = power;
	pixmapCache.clear();
	update();
}

void Spectrogram::setZoomLevel(int zoom)
{
	zoomLevel = clamp(zoom, 0, (int)log2(fftSize));
	resize(fftSize, getHeight());
}

int Spectrogram::getHeight()
{
	if (!inputSource)
		return 0;

	return inputSource->getSampleCount() / getStride();
}

int Spectrogram::getStride()
{
	return fftSize / pow(2, zoomLevel);
}

off_t Spectrogram::lineToSample(int line) {
	return line * getStride();
}

int Spectrogram::sampleToLine(off_t sample) {
	return sample / getStride();
}

QString Spectrogram::sampleToTime(off_t sample)
{
	return QString::number((float)sample / sampleRate).append("s");
}

int Spectrogram::linesPerTile() {
	return tileSize / fftSize;
}

uint qHash(const TileCacheKey &key, uint seed) {
	return key.fftSize ^ key.zoomLevel ^ key.sample ^ seed;
}