sdrtrunk/src/main/java/io/github/dsheirer/buffer/sample/ScalarPackedSampleConverter.java

/*
 * *****************************************************************************
 * Copyright (C) 2014-2025 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 io.github.dsheirer.buffer.sample;

import io.github.dsheirer.buffer.DcCorrectionManager;
import java.nio.ByteBuffer;

/**
 * Scalar implementation of sample converter for un-packed samples.
 */
public class ScalarPackedSampleConverter implements ISampleConverter
{
    /**
     * Manages DC calculations and processing interval
     */
    private DcCorrectionManager mDcCalculationManager = new DcCorrectionManager();

    @Override
    public short[] convert(ByteBuffer buffer)
    {
        boolean shouldCalculateDc = mDcCalculationManager.shouldCalculateDc();

        int offset = 0;
        short sample;
        short[] samples;
        byte b1, b2, b3;

        samples = new short[buffer.capacity() / 3 * 2];

        if(shouldCalculateDc)
        {
            long dcAccumulator = 0;

            for(int x = 0; x < samples.length; x += 2)
            {
                b1 = buffer.get(offset++);
                b2 = buffer.get(offset++);
                b3 = buffer.get(offset++);

                sample = (short)(((b1 & 0xFF) << 4) | ((b2 & 0xF0) >> 4));
                samples[x] = sample;
                dcAccumulator += sample;

                sample = (short)(((b2 & 0xF) << 8) | (b3 & 0xFF));
                samples[x] = sample;
                dcAccumulator += sample;
            }

            float averageDcNow = ((float)dcAccumulator / (float)samples.length) - 2048.0f;
            averageDcNow *= SampleBufferIterator.SCALE_SIGNED_12_BIT_TO_FLOAT;
            mDcCalculationManager.adjust(averageDcNow);
        }
        else
        {
            for(int x = 0; x < samples.length; x += 2)
            {
                b1 = buffer.get(offset++);
                b2 = buffer.get(offset++);
                b3 = buffer.get(offset++);

                sample = (short)(((b1 & 0xFF) << 4) | ((b2 & 0xF0) >> 4));
                samples[x] = sample;

                sample = (short)(((b2 & 0xF) << 8) | (b3 & 0xFF));
                samples[x] = sample;
            }
        }

        return samples;
    }

    @Override
    public float getAverageDc()
    {
        return mDcCalculationManager.getAverageDc();
    }

    public static void main(String[] args)
    {
        byte[] raw = new byte[262144];
        ByteBuffer buffer = ByteBuffer.wrap(raw);

        ScalarPackedSampleConverter scalar = new ScalarPackedSampleConverter();
        VectorUnpackedSampleConverter vector = new VectorUnpackedSampleConverter();

        long accumulator = 0;
        int iterations = 1_000_000;

        System.out.println("Starting ...");
        long start = System.currentTimeMillis();
        for(int count = 0; count < iterations; count++)
        {
//            short[] samples = scalar.convert(buffer);
            short[] samples = vector.convert(buffer);
            accumulator += samples[1];
        }
        long elapsed = System.currentTimeMillis() - start;

        System.out.println("Accumulator: " + accumulator);
        System.out.println("Elapsed: " + (elapsed / 1000.0f));
        System.out.println("Finished");
    }
}