/*
 *  ReplayGainAnalysis - analyzes input samples and give the recommended dB change
 *  Copyright (C) 2001 David Robinson and Glen Sawyer
 *  Improvements and optimizations added by Frank Klemm, and by Marcel Muller 
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library 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
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *  concept and filter values by David Robinson (David@Robinson.org)
 *    -- blame him if you think the idea is flawed
 *  original coding by Glen Sawyer (mp3gain@hotmail.com)
 *    -- blame him if you think this runs too slowly, or the coding is otherwise flawed
 *
 *  lots of code improvements by Frank Klemm ( http://www.uni-jena.de/~pfk/mpp/ )
 *    -- credit him for all the _good_ programming ;)
 *
 *
 *  For an explanation of the concepts and the basic algorithms involved, go to:
 *    http://www.replaygain.org/
 */

/*
 *  Here's the deal. Call
 *
 *    InitGainAnalysis ( long samplefreq );
 *
 *  to initialize everything. Call
 *
 *    AnalyzeSamples ( const Float_t*  left_samples,
 *                     const Float_t*  right_samples,
 *                     size_t          num_samples,
 *                     int             num_channels );
 *
 *  as many times as you want, with as many or as few samples as you want.
 *  If mono, pass the sample buffer in through left_samples, leave
 *  right_samples NULL, and make sure num_channels = 1.
 *
 *    GetTitleGain()
 *
 *  will return the recommended dB level change for all samples analyzed
 *  SINCE THE LAST TIME you called GetTitleGain() OR InitGainAnalysis().
 *
 *    GetAlbumGain()
 *
 *  will return the recommended dB level change for all samples analyzed
 *  since InitGainAnalysis() was called and finalized with GetTitleGain().
 *
 *  Pseudo-code to process an album:
 *
 *    Float_t       l_samples [4096];
 *    Float_t       r_samples [4096];
 *    size_t        num_samples;
 *    unsigned int  num_songs;
 *    unsigned int  i;
 *
 *    InitGainAnalysis ( 44100 );
 *    for ( i = 1; i <= num_songs; i++ ) {
 *        while ( ( num_samples = getSongSamples ( song[i], left_samples, right_samples ) ) > 0 )
 *            AnalyzeSamples ( left_samples, right_samples, num_samples, 2 );
 *        fprintf ("Recommended dB change for song %2d: %+6.2f dB\n", i, GetTitleGain() );
 *    }
 *    fprintf ("Recommended dB change for whole album: %+6.2f dB\n", GetAlbumGain() );
 */

/*
 *  So here's the main source of potential code confusion:
 *
 *  The filters applied to the incoming samples are IIR filters,
 *  meaning they rely on up to <filter order> number of previous samples
 *  AND up to <filter order> number of previous filtered samples.
 *
 *  I set up the AnalyzeSamples routine to minimize memory usage and interface
 *  complexity. The speed isn't compromised too much (I don't think), but the
 *  internal complexity is higher than it should be for such a relatively
 *  simple routine.
 *
 *  Optimization/clarity suggestions are welcome.
 */
package mp3;

import java.util.Arrays;

public class GainAnalysis {
	/**
	 * calibration value for 89dB
	 */
	private static final float PINK_REF = 64.82f;

	private static final int YULE_ORDER = 10;
	/**
	 * percentile which is louder than the proposed level
	 */
	private static final float RMS_PERCENTILE = 0.95f;
	/**
	 * maximum allowed sample frequency [Hz]
	 */
	private static final int MAX_SAMP_FREQ = 48000;
	private static final int RMS_WINDOW_TIME_NUMERATOR = 1;
	/**
	 * numerator / denominator = time slice size [s]
	 */
	private static final int RMS_WINDOW_TIME_DENOMINATOR = 20;
	/**
	 * Table entries per dB
	 */
	static final float STEPS_per_dB = 100.f;
	/**
	 * Table entries for 0...MAX_dB (normal max. values are 70...80 dB)
	 */
	static final float MAX_dB = 120.f;

	public static final int GAIN_NOT_ENOUGH_SAMPLES = -24601;
	public static final int GAIN_ANALYSIS_ERROR = 0;
	public static final int GAIN_ANALYSIS_OK = 1;
	public static final int INIT_GAIN_ANALYSIS_ERROR = 0;
	public static final int INIT_GAIN_ANALYSIS_OK = 1;

    static final int MAX_ORDER = YULE_ORDER;
	/**
	 * max. Samples per Time slice
	 */
	static final int MAX_SAMPLES_PER_WINDOW = ((MAX_SAMP_FREQ * RMS_WINDOW_TIME_NUMERATOR)
			/ RMS_WINDOW_TIME_DENOMINATOR + 1);
    
	private static final float ABYule[][] = {
			{ 0.03857599435200f, -3.84664617118067f, -0.02160367184185f,
					7.81501653005538f, -0.00123395316851f, -11.34170355132042f,
					-0.00009291677959f, 13.05504219327545f, -0.01655260341619f,
					-12.28759895145294f, 0.02161526843274f, 9.48293806319790f,
					-0.02074045215285f, -5.87257861775999f, 0.00594298065125f,
					2.75465861874613f, 0.00306428023191f, -0.86984376593551f,
					0.00012025322027f, 0.13919314567432f, 0.00288463683916f },
			{ 0.05418656406430f, -3.47845948550071f, -0.02911007808948f,
					6.36317777566148f, -0.00848709379851f, -8.54751527471874f,
					-0.00851165645469f, 9.47693607801280f, -0.00834990904936f,
					-8.81498681370155f, 0.02245293253339f, 6.85401540936998f,
					-0.02596338512915f, -4.39470996079559f, 0.01624864962975f,
					2.19611684890774f, -0.00240879051584f, -0.75104302451432f,
					0.00674613682247f, 0.13149317958808f, -0.00187763777362f },
			{ 0.15457299681924f, -2.37898834973084f, -0.09331049056315f,
					2.84868151156327f, -0.06247880153653f, -2.64577170229825f,
					0.02163541888798f, 2.23697657451713f, -0.05588393329856f,
					-1.67148153367602f, 0.04781476674921f, 1.00595954808547f,
					0.00222312597743f, -0.45953458054983f, 0.03174092540049f,
					0.16378164858596f, -0.01390589421898f, -0.05032077717131f,
					0.00651420667831f, 0.02347897407020f, -0.00881362733839f },
			{ 0.30296907319327f, -1.61273165137247f, -0.22613988682123f,
					1.07977492259970f, -0.08587323730772f, -0.25656257754070f,
					0.03282930172664f, -0.16276719120440f, -0.00915702933434f,
					-0.22638893773906f, -0.02364141202522f, 0.39120800788284f,
					-0.00584456039913f, -0.22138138954925f, 0.06276101321749f,
					0.04500235387352f, -0.00000828086748f, 0.02005851806501f,
					0.00205861885564f, 0.00302439095741f, -0.02950134983287f },
			{ 0.33642304856132f, -1.49858979367799f, -0.25572241425570f,
					0.87350271418188f, -0.11828570177555f, 0.12205022308084f,
					0.11921148675203f, -0.80774944671438f, -0.07834489609479f,
					0.47854794562326f, -0.00469977914380f, -0.12453458140019f,
					-0.00589500224440f, -0.04067510197014f, 0.05724228140351f,
					0.08333755284107f, 0.00832043980773f, -0.04237348025746f,
					-0.01635381384540f, 0.02977207319925f, -0.01760176568150f },
			{ 0.44915256608450f, -0.62820619233671f, -0.14351757464547f,
					0.29661783706366f, -0.22784394429749f, -0.37256372942400f,
					-0.01419140100551f, 0.00213767857124f, 0.04078262797139f,
					-0.42029820170918f, -0.12398163381748f, 0.22199650564824f,
					0.04097565135648f, 0.00613424350682f, 0.10478503600251f,
					0.06747620744683f, -0.01863887810927f, 0.05784820375801f,
					-0.03193428438915f, 0.03222754072173f, 0.00541907748707f },
			{ 0.56619470757641f, -1.04800335126349f, -0.75464456939302f,
					0.29156311971249f, 0.16242137742230f, -0.26806001042947f,
					0.16744243493672f, 0.00819999645858f, -0.18901604199609f,
					0.45054734505008f, 0.30931782841830f, -0.33032403314006f,
					-0.27562961986224f, 0.06739368333110f, 0.00647310677246f,
					-0.04784254229033f, 0.08647503780351f, 0.01639907836189f,
					-0.03788984554840f, 0.01807364323573f, -0.00588215443421f },
			{ 0.58100494960553f, -0.51035327095184f, -0.53174909058578f,
					-0.31863563325245f, -0.14289799034253f, -0.20256413484477f,
					0.17520704835522f, 0.14728154134330f, 0.02377945217615f,
					0.38952639978999f, 0.15558449135573f, -0.23313271880868f,
					-0.25344790059353f, -0.05246019024463f, 0.01628462406333f,
					-0.02505961724053f, 0.06920467763959f, 0.02442357316099f,
					-0.03721611395801f, 0.01818801111503f, -0.00749618797172f },
			{ 0.53648789255105f, -0.25049871956020f, -0.42163034350696f,
					-0.43193942311114f, -0.00275953611929f, -0.03424681017675f,
					0.04267842219415f, -0.04678328784242f, -0.10214864179676f,
					0.26408300200955f, 0.14590772289388f, 0.15113130533216f,
					-0.02459864859345f, -0.17556493366449f, -0.11202315195388f,
					-0.18823009262115f, -0.04060034127000f, 0.05477720428674f,
					0.04788665548180f, 0.04704409688120f, -0.02217936801134f } };

	private static final float ABButter[][] = {
			{ 0.98621192462708f, -1.97223372919527f, -1.97242384925416f,
					0.97261396931306f, 0.98621192462708f },
			{ 0.98500175787242f, -1.96977855582618f, -1.97000351574484f,
					0.97022847566350f, 0.98500175787242f },
			{ 0.97938932735214f, -1.95835380975398f, -1.95877865470428f,
					0.95920349965459f, 0.97938932735214f },
			{ 0.97531843204928f, -1.95002759149878f, -1.95063686409857f,
					0.95124613669835f, 0.97531843204928f },
			{ 0.97316523498161f, -1.94561023566527f, -1.94633046996323f,
					0.94705070426118f, 0.97316523498161f },
			{ 0.96454515552826f, -1.92783286977036f, -1.92909031105652f,
					0.93034775234268f, 0.96454515552826f },
			{ 0.96009142950541f, -1.91858953033784f, -1.92018285901082f,
					0.92177618768381f, 0.96009142950541f },
			{ 0.95856916599601f, -1.91542108074780f, -1.91713833199203f,
					0.91885558323625f, 0.95856916599601f },
			{ 0.94597685600279f, -1.88903307939452f, -1.89195371200558f,
					0.89487434461664f, 0.94597685600279f } };


	/**
	 * When calling this procedure, make sure that ip[-order] and op[-order]
	 * point to real data
	 */
	private void filterYule(final float[] input, int inputPos, float[] output,
			int outputPos, int nSamples, final float[] kernel) {

		while ((nSamples--) != 0) {
			/* 1e-10 is a hack to avoid slowdown because of denormals */
			output[outputPos] = 1e-10f + input[inputPos + 0] * kernel[0]
					- output[outputPos - 1] * kernel[1] + input[inputPos - 1]
					* kernel[2] - output[outputPos - 2] * kernel[3]
					+ input[inputPos - 2] * kernel[4] - output[outputPos - 3]
					* kernel[5] + input[inputPos - 3] * kernel[6]
					- output[outputPos - 4] * kernel[7] + input[inputPos - 4]
					* kernel[8] - output[outputPos - 5] * kernel[9]
					+ input[inputPos - 5] * kernel[10] - output[outputPos - 6]
					* kernel[11] + input[inputPos - 6] * kernel[12]
					- output[outputPos - 7] * kernel[13] + input[inputPos - 7]
					* kernel[14] - output[outputPos - 8] * kernel[15]
					+ input[inputPos - 8] * kernel[16] - output[outputPos - 9]
					* kernel[17] + input[inputPos - 9] * kernel[18]
					- output[outputPos - 10] * kernel[19]
					+ input[inputPos - 10] * kernel[20];
			++outputPos;
			++inputPos;
		}
    }

	private void filterButter(final float[] input, int inputPos,
			float[] output, int outputPos, int nSamples, final float[] kernel) {

		while ((nSamples--) != 0) {
			output[outputPos] = input[inputPos + 0] * kernel[0]
					- output[outputPos - 1] * kernel[1] + input[inputPos - 1]
					* kernel[2] - output[outputPos - 2] * kernel[3]
					+ input[inputPos - 2] * kernel[4];
			++outputPos;
			++inputPos;
		}
	}

	/**
	 * @return INIT_GAIN_ANALYSIS_OK if successful, INIT_GAIN_ANALYSIS_ERROR if
	 *         not
	 */
	private int ResetSampleFrequency(final ReplayGain rgData,
			final long samplefreq) {
		/* zero out initial values */
		for (int i = 0; i < MAX_ORDER; i++)
			rgData.linprebuf[i] = rgData.lstepbuf[i] = rgData.loutbuf[i] = rgData.rinprebuf[i] = rgData.rstepbuf[i] = rgData.routbuf[i] = 0.f;

		switch ((int) (samplefreq)) {
		case 48000:
			rgData.freqindex = 0;
			break;
		case 44100:
			rgData.freqindex = 1;
			break;
		case 32000:
			rgData.freqindex = 2;
			break;
		case 24000:
			rgData.freqindex = 3;
			break;
		case 22050:
			rgData.freqindex = 4;
			break;
		case 16000:
			rgData.freqindex = 5;
			break;
		case 12000:
			rgData.freqindex = 6;
			break;
		case 11025:
			rgData.freqindex = 7;
			break;
		case 8000:
			rgData.freqindex = 8;
			break;
		default:
			return INIT_GAIN_ANALYSIS_ERROR;
		}

		rgData.sampleWindow = (int) ((samplefreq * RMS_WINDOW_TIME_NUMERATOR
				+ RMS_WINDOW_TIME_DENOMINATOR - 1) / RMS_WINDOW_TIME_DENOMINATOR);

		rgData.lsum = 0.;
		rgData.rsum = 0.;
		rgData.totsamp = 0;

		Arrays.fill(rgData.A, 0);

		return INIT_GAIN_ANALYSIS_OK;
	}

	public final int InitGainAnalysis(final ReplayGain rgData,
			final long samplefreq) {
		if (ResetSampleFrequency(rgData, samplefreq) != INIT_GAIN_ANALYSIS_OK) {
			return INIT_GAIN_ANALYSIS_ERROR;
		}

		rgData.linpre = MAX_ORDER;
		rgData.rinpre = MAX_ORDER;
		rgData.lstep = MAX_ORDER;
		rgData.rstep = MAX_ORDER;
		rgData.lout = MAX_ORDER;
		rgData.rout = MAX_ORDER;

		Arrays.fill(rgData.B, 0);

		return INIT_GAIN_ANALYSIS_OK;
	}

	/**
	 * square
	 */
	private double fsqr(final double d) {
		return d * d;
	}

	public final int AnalyzeSamples(final ReplayGain rgData,
			final float[] left_samples, final int left_samplesPos,
			float[] right_samples, int right_samplesPos, final int num_samples,
			final int num_channels) {
		int curleft;
		float[] curleftBase;
		int curright;
		float[] currightBase;
		int batchsamples;
		int cursamples;
		int cursamplepos;

		if (num_samples == 0)
			return GAIN_ANALYSIS_OK;

		cursamplepos = 0;
		batchsamples = num_samples;

		switch (num_channels) {
		case 1:
			right_samples = left_samples;
			right_samplesPos = left_samplesPos;
			break;
		case 2:
			break;
		default:
			return GAIN_ANALYSIS_ERROR;
		}

		if (num_samples < MAX_ORDER) {
			System.arraycopy(left_samples, left_samplesPos, rgData.linprebuf,
					MAX_ORDER, num_samples);
			System.arraycopy(right_samples, right_samplesPos, rgData.rinprebuf,
					MAX_ORDER, num_samples);
		} else {
			System.arraycopy(left_samples, left_samplesPos, rgData.linprebuf,
					MAX_ORDER, MAX_ORDER);
			System.arraycopy(right_samples, right_samplesPos, rgData.rinprebuf,
					MAX_ORDER, MAX_ORDER);
		}

		while (batchsamples > 0) {
			cursamples = batchsamples > rgData.sampleWindow - rgData.totsamp ? rgData.sampleWindow
					- rgData.totsamp
					: batchsamples;
			if (cursamplepos < MAX_ORDER) {
				curleft = rgData.linpre + cursamplepos;
				curleftBase = rgData.linprebuf;
				curright = rgData.rinpre + cursamplepos;
				currightBase = rgData.rinprebuf;
				if (cursamples > MAX_ORDER - cursamplepos)
					cursamples = MAX_ORDER - cursamplepos;
			} else {
				curleft = left_samplesPos + cursamplepos;
				curleftBase = left_samples;
				curright = right_samplesPos + cursamplepos;
				currightBase = right_samples;
			}

			filterYule(curleftBase, curleft, rgData.lstepbuf, rgData.lstep
					+ rgData.totsamp, cursamples, ABYule[rgData.freqindex]);
			filterYule(currightBase, curright, rgData.rstepbuf, rgData.rstep
					+ rgData.totsamp, cursamples, ABYule[rgData.freqindex]);

			filterButter(rgData.lstepbuf, rgData.lstep + rgData.totsamp,
					rgData.loutbuf, rgData.lout + rgData.totsamp, cursamples,
					ABButter[rgData.freqindex]);
			filterButter(rgData.rstepbuf, rgData.rstep + rgData.totsamp,
					rgData.routbuf, rgData.rout + rgData.totsamp, cursamples,
					ABButter[rgData.freqindex]);

			curleft = rgData.lout + rgData.totsamp;
			/* Get the squared values */
			curleftBase = rgData.loutbuf;
			curright = rgData.rout + rgData.totsamp;
			currightBase = rgData.routbuf;

			int i = cursamples % 8;
			while ((i--) != 0) {
				rgData.lsum += fsqr(curleftBase[curleft++]);
				rgData.rsum += fsqr(currightBase[curright++]);
			}
			i = cursamples / 8;
			while ((i--) != 0) {
				rgData.lsum += fsqr(curleftBase[curleft + 0])
						+ fsqr(curleftBase[curleft + 1])
						+ fsqr(curleftBase[curleft + 2])
						+ fsqr(curleftBase[curleft + 3])
						+ fsqr(curleftBase[curleft + 4])
						+ fsqr(curleftBase[curleft + 5])
						+ fsqr(curleftBase[curleft + 6])
						+ fsqr(curleftBase[curleft + 7]);
				curleft += 8;
				rgData.rsum += fsqr(currightBase[curright + 0])
						+ fsqr(currightBase[curright + 1])
						+ fsqr(currightBase[curright + 2])
						+ fsqr(currightBase[curright + 3])
						+ fsqr(currightBase[curright + 4])
						+ fsqr(currightBase[curright + 5])
						+ fsqr(currightBase[curright + 6])
						+ fsqr(currightBase[curright + 7]);
				curright += 8;
			}

			batchsamples -= cursamples;
			cursamplepos += cursamples;
			rgData.totsamp += cursamples;
			if (rgData.totsamp == rgData.sampleWindow) {
				/* Get the Root Mean Square (RMS) for this set of samples */
				final double val = STEPS_per_dB
						* 10.
						* Math.log10((rgData.lsum + rgData.rsum)
								/ rgData.totsamp * 0.5 + 1.e-37);
				int ival = (val <= 0) ? 0 : (int) val;
				if (ival >= rgData.A.length)
					ival = rgData.A.length - 1;
				rgData.A[ival]++;
				rgData.lsum = rgData.rsum = 0.;

				System.arraycopy(rgData.loutbuf, rgData.totsamp,
						rgData.loutbuf, 0, MAX_ORDER);
				System.arraycopy(rgData.routbuf, rgData.totsamp,
						rgData.routbuf, 0, MAX_ORDER);
				System.arraycopy(rgData.lstepbuf, rgData.totsamp,
						rgData.lstepbuf, 0, MAX_ORDER);
				System.arraycopy(rgData.rstepbuf, rgData.totsamp,
						rgData.rstepbuf, 0, MAX_ORDER);
				rgData.totsamp = 0;
			}
			if (rgData.totsamp > rgData.sampleWindow) {
				/*
				 * somehow I really screwed up: Error in programming! Contact
				 * author about totsamp > sampleWindow
				 */
				return GAIN_ANALYSIS_ERROR;
			}
		}
		if (num_samples < MAX_ORDER) {
			System.arraycopy(rgData.linprebuf, num_samples, rgData.linprebuf,
					0, MAX_ORDER - num_samples);
			System.arraycopy(rgData.rinprebuf, num_samples, rgData.rinprebuf,
					0, MAX_ORDER - num_samples);
			System.arraycopy(left_samples, left_samplesPos, rgData.linprebuf,
					MAX_ORDER - num_samples, num_samples);
			System.arraycopy(right_samples, right_samplesPos, rgData.rinprebuf,
					MAX_ORDER - num_samples, num_samples);
		} else {
			System.arraycopy(left_samples, left_samplesPos + num_samples
					- MAX_ORDER, rgData.linprebuf, 0, MAX_ORDER);
			System.arraycopy(right_samples, right_samplesPos + num_samples
					- MAX_ORDER, rgData.rinprebuf, 0, MAX_ORDER);
		}

		return GAIN_ANALYSIS_OK;
	}

	private float analyzeResult(final int[] Array, final int len) {
		int i;

		int elems = 0;
		for (i = 0; i < len; i++)
			elems += Array[i];
		if (elems == 0)
			return GAIN_NOT_ENOUGH_SAMPLES;

		int upper = (int) Math.ceil(elems * (1. - RMS_PERCENTILE));
		for (i = len; i-- > 0;) {
			if ((upper -= Array[i]) <= 0)
				break;
		}

		return (float) ((float) PINK_REF - (float) i / (float) STEPS_per_dB);
	}

	public final float GetTitleGain(final ReplayGain rgData) {
		float retval = analyzeResult(rgData.A, rgData.A.length);

		for (int i = 0; i < rgData.A.length; i++) {
			rgData.B[i] += rgData.A[i];
			rgData.A[i] = 0;
		}

		for (int i = 0; i < MAX_ORDER; i++)
			rgData.linprebuf[i] = rgData.lstepbuf[i] = rgData.loutbuf[i] = rgData.rinprebuf[i] = rgData.rstepbuf[i] = rgData.routbuf[i] = 0.f;

		rgData.totsamp = 0;
		rgData.lsum = rgData.rsum = 0.;
		return retval;
	}

}