sdrtrunk/src/spectrum/DFTProcessor.java

/*******************************************************************************
 * sdrtrunk
 * Copyright (C) 2014-2017 Dennis Sheirer
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 *
 ******************************************************************************/
package spectrum;

import dsp.filter.Window;
import dsp.filter.Window.WindowType;
import org.jtransforms.fft.FloatFFT_1D;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import properties.SystemProperties;
import sample.Buffer;
import sample.Listener;
import sample.SampleType;
import sample.complex.ComplexBuffer;
import source.tuner.frequency.FrequencyChangeEvent;
import source.tuner.frequency.IFrequencyChangeProcessor;
import spectrum.converter.DFTResultsConverter;
import util.ThreadPool;

import java.util.Arrays;
import java.util.Iterator;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * Processes both complex samples or float samples and dispatches a float array
 * of DFT results, using configurable fft size and output dispatch timelines.
 */
public class DFTProcessor implements Listener<ComplexBuffer>, IFrequencyChangeProcessor, IDFTWidthChangeProcessor
{
    private final static Logger mLog = LoggerFactory.getLogger(DFTProcessor.class);

    private CopyOnWriteArrayList<DFTResultsConverter> mListeners = new CopyOnWriteArrayList<DFTResultsConverter>();

    //Fixed size sample queue.  We set the size at 12 based on the highest
    //sample rate tuner (10 MHz) producing 153 frames per second and the lowest
    //DFT processing frame rate of 12 frames per second.  This means that the
    //maximum size needed is 153 / 12 = 11 frames per DFT processing iteration
    //so we set it at 12.
    private BlockingQueue<ComplexBuffer> mQueue = new ArrayBlockingQueue<>(12);

    private ScheduledFuture<?> mProcessorTaskHandle;

    public static final String FRAME_RATE_PROPERTY = "spectral.display.frame.rate";

    private DFTSize mDFTSize = DFTSize.FFT04096;
    private DFTSize mNewDFTSize = DFTSize.FFT04096;

    private double[] mWindow;

    /* The Cosine and Hanning windows seem to offer the best spectral display
     * with minimal bin leakage/smearing */
    private WindowType mWindowType = Window.WindowType.HANNING;

    private FloatFFT_1D mFFT = new FloatFFT_1D(mDFTSize.getSize());

    private int mFrameRate;
    private int mSampleRate;
    private int mFFTFloatsPerFrame;
    private float mNewFloatsPerFrame;
    private float mNewFloatResidual;
    private float[] mPreviousFrame = new float[8192];

    private float[] mCurrentBuffer;
    private int mCurrentBufferPointer = 0;

    private SampleType mSampleType;

    private AtomicBoolean mRunning = new AtomicBoolean();

    public DFTProcessor(SampleType sampleType)
    {
        setSampleType(sampleType);
        mFrameRate = SystemProperties.getInstance().get(FRAME_RATE_PROPERTY, 20);
        calculateConsumptionRate();
        start();
    }

    public void dispose()
    {
        stop();

        mListeners.clear();
        mQueue.clear();
        mWindow = null;
        mCurrentBuffer = null;
    }

    public WindowType getWindowType()
    {
        return mWindowType;
    }

    public void setWindowType(WindowType windowType)
    {
        mWindowType = windowType;

        if(mSampleType == SampleType.COMPLEX)
        {
            mWindow = Window.getWindow(mWindowType, mDFTSize.getSize() * 2);
        }
        else
        {
            mWindow = Window.getWindow(mWindowType, mDFTSize.getSize());
        }
    }

    /**
     * Sets the processor mode to Float or Complex, depending on the sample
     * types that will be delivered for processing
     */
    public void setSampleType(SampleType type)
    {
        mSampleType = type;
        setWindowType(mWindowType);
    }

    public SampleType getSampleType()
    {
        return mSampleType;
    }

    /**
     * Queues an FFT size change request.  The scheduled executor will apply
     * the change when it runs.
     */
    public void setDFTSize(DFTSize size)
    {
        mNewDFTSize = size;
    }

    public DFTSize getDFTSize()
    {
        return mDFTSize;
    }

    public int getFrameRate()
    {
        return mFrameRate;
    }

    public void setFrameRate(int framesPerSecond)
    {
        //TODO: make sure frame rate & sample rate sample requirement doesn't
        //expect overlap greater than the previous frame length

        if(framesPerSecond < 1 || framesPerSecond > 1000)
        {
            throw new IllegalArgumentException("DFTProcessor cannot run "
                + "more than 1000 times per second -- requested setting:"
                + framesPerSecond);
        }

        mFrameRate = framesPerSecond;

        SystemProperties.getInstance().set(FRAME_RATE_PROPERTY, mFrameRate);

        calculateConsumptionRate();

        restart();
    }

    public void start()
    {
        //Schedule the DFT to run calculations at a fixed rate
        int initialDelay = 0;
        int period = (int) (1000 / mFrameRate);

        mProcessorTaskHandle = ThreadPool.SCHEDULED.scheduleAtFixedRate(new DFTCalculationTask(), initialDelay, period,
            TimeUnit.MILLISECONDS);
    }

    public void stop()
    {
        //Cancel running DFT calculation task
        if(mProcessorTaskHandle != null)
        {
            mProcessorTaskHandle.cancel(true);
        }
    }

    public void restart()
    {
        stop();
        start();
    }

    public int getCalculationsPerSecond()
    {
        return mFrameRate;
    }

    /**
     * Places the sample into a transfer queue for future processing.
     */
    @Override
    public void receive(ComplexBuffer sampleBuffer)
    {
        mQueue.offer(sampleBuffer);
    }

    private void getNextBuffer()
    {
        mCurrentBuffer = null;

        try
        {
            Buffer buffer = mQueue.take();
            mCurrentBuffer = buffer.getSamples();
        }
        catch(InterruptedException e)
        {
            mCurrentBuffer = null;
        }

        mCurrentBufferPointer = 0;
    }

    private float[] getSamples()
    {
        int remaining = (int) mFFTFloatsPerFrame;

        float[] currentFrame = new float[remaining];

        int currentFramePointer = 0;

        float integralFloatsToConsume = mNewFloatsPerFrame + mNewFloatResidual;

        int newFloatsToConsumeThisFrame = (int) integralFloatsToConsume;

        mNewFloatResidual = integralFloatsToConsume - newFloatsToConsumeThisFrame;
		
		/* If the number of required floats for the fft is greater than the
		 * consumption rate per frame, we have to reach into the previous
		 * frame to makeup the difference. */
        if(newFloatsToConsumeThisFrame < remaining)
        {
            int previousFloatsRequired = remaining - newFloatsToConsumeThisFrame;

            System.arraycopy(mPreviousFrame,
                mPreviousFrame.length - previousFloatsRequired,
                currentFrame,
                currentFramePointer,
                previousFloatsRequired);

            remaining -= previousFloatsRequired;
            currentFramePointer += previousFloatsRequired;
        }

		/* Fill the rest of the buffer with new samples */
        while(mRunning.get() && remaining > 0)
        {
            if(mCurrentBuffer == null ||
                mCurrentBufferPointer >= mCurrentBuffer.length)
            {
                getNextBuffer();
            }

			/* If we don't have new samples to use, send the current frame with
			 * the remaining values as zero */
            if(mCurrentBuffer == null)
            {
                remaining = 0;
            }
            else
            {
                int samplesAvailable = mCurrentBuffer.length - mCurrentBufferPointer;

                while(remaining > 0 && samplesAvailable > 0)
                {
                    currentFrame[currentFramePointer++] =
                        (float) mCurrentBuffer[mCurrentBufferPointer++];

                    samplesAvailable--;
                    remaining--;
                    newFloatsToConsumeThisFrame--;
                }
            }
        }
		
		/* If the incoming float rate is greater than the fft consumption rate,
		 * then we have to purge some floats, otherwise, store the previous
		 * frame, because we have overlapping frames */
        if(newFloatsToConsumeThisFrame > 0)
        {
            purge(newFloatsToConsumeThisFrame);
        }
        else
        {
            mPreviousFrame = Arrays.copyOf(currentFrame, currentFrame.length);
        }

        return currentFrame;
    }

    private void calculate()
    {
        float[] samples = getSamples();

        Window.apply(mWindow, samples);

        if(mSampleType == SampleType.REAL)
        {
            mFFT.realForward(samples);
        }
        else
        {
            mFFT.complexForward(samples);
        }

        dispatch(samples);
    }


    private void purge(int samplesToPurge)
    {
        if(samplesToPurge <= 0)
        {
            throw new IllegalArgumentException("DFTProcessor - cannot purge "
                + "negative sample amount");
        }

        while(mRunning.get() && samplesToPurge > 0)
        {
            if(mCurrentBuffer == null ||
                mCurrentBufferPointer >= mCurrentBuffer.length)
            {
                getNextBuffer();
            }

            if(mCurrentBuffer != null)
            {
                int samplesAvailable = mCurrentBuffer.length - mCurrentBufferPointer;

                if(samplesAvailable >= samplesToPurge)
                {
                    mCurrentBufferPointer += samplesToPurge;
                    samplesToPurge = 0;
                }
                else
                {
                    samplesToPurge -= samplesAvailable;
                    mCurrentBufferPointer = mCurrentBuffer.length;
                }
            }
            else
            {
                samplesToPurge = 0;
            }
        }
    }

    /**
     * Takes a calculated DFT results set, reformats the data, and sends it
     * out to all registered listeners.
     */
    private void dispatch(float[] results)
    {
        Iterator<DFTResultsConverter> it = mListeners.iterator();

        while(it.hasNext())
        {
            it.next().receive(results);
        }
    }

    public void addConverter(DFTResultsConverter listener)
    {
        mListeners.add(listener);
    }

    public void removeConverter(DFTResultsConverter listener)
    {
        mListeners.remove(listener);
    }

    private class DFTCalculationTask implements Runnable
    {
        @Override
        public void run()
        {
            try
            {
				/* Only run if we're not currently running */
                if(mRunning.compareAndSet(false, true))
                {
                    checkFFTSize();

                    calculate();

                    mRunning.set(false);
                }
            }
            catch(Exception e)
            {
                mLog.error("error during dft processor calculation task", e);
            }
        }
    }

    /**
     * Checks for a queued FFT width change request and applies it.  This
     * method will only be accessed by the scheduled executor that gains
     * access to run a calculate method, thus providing thread safety.
     */
    private void checkFFTSize()
    {
        if(mNewDFTSize.getSize() != mDFTSize.getSize())
        {
            mDFTSize = mNewDFTSize;

            calculateConsumptionRate();

            setWindowType(mWindowType);

            if(mSampleType == SampleType.COMPLEX)
            {
                mPreviousFrame = new float[mDFTSize.getSize() * 2];
            }
            else
            {
                mPreviousFrame = new float[mDFTSize.getSize()];
            }

            mFFT = new FloatFFT_1D(mDFTSize.getSize());
        }
    }

    public void clearBuffer()
    {
        mQueue.clear();
    }

    @Override
    public void frequencyChanged(FrequencyChangeEvent event)
    {
        switch(event.getEvent())
        {
            case NOTIFICATION_SAMPLE_RATE_CHANGE:
                mSampleRate = event.getValue().intValue();
                calculateConsumptionRate();
                break;
            default:
                break;
        }
    }

    /**
     *
     */
    private void calculateConsumptionRate()
    {
        mNewFloatResidual = 0.0f;

        mNewFloatsPerFrame = ((float) mSampleRate / (float) mFrameRate) *
            (mSampleType == SampleType.COMPLEX ? 2.0f : 1.0f);

        mFFTFloatsPerFrame = (mSampleType == SampleType.COMPLEX ?
            mDFTSize.getSize() * 2 :
            mDFTSize.getSize());
    }
}