/*

  * Copyright (c) 2002-2014, Mairie de Paris

  * All rights reserved.

  *

  * Redistribution and use in source and binary forms, with or without

  * modification, are permitted provided that the following conditions

  * are met:

  *

  *  1. Redistributions of source code must retain the above copyright notice

  *     and the following disclaimer.

  *

  *  2. Redistributions in binary form must reproduce the above copyright notice

  *     and the following disclaimer in the documentation and/or other materials

  *     provided with the distribution.

  *

  *  3. Neither the name of 'Mairie de Paris' nor 'Lutece' nor the names of its

  *     contributors may be used to endorse or promote products derived from

  *     this software without specific prior written permission.

  *

  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE

  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

  * POSSIBILITY OF SUCH DAMAGE.

  *

  * License 1.0

  */

 package fr.paris.lutece.plugins.captcha.modules.jcaptcha.service.sound.filter;

 import fr.paris.lutece.plugins.captcha.modules.jcaptcha.service.sound.LuteceWordToSound;

 /**

  *

  */

 public class EchoFilter extends SoundFilter

 {

     private short[] _delayBuffer;

     private int _delayBufferPos;

     private float _decay;

     /**

      * Creates an EchoFilter with the specified number of delay samples and the

      * specified decay rate.

      * <p>

      * The number of delay samples specifies how long before the echo is

      * initially heard. For a 1 second echo with mono, 44100Hz sound, use 44100

      * delay samples.

      * <p>

      * The decay value is how much the echo has decayed from the source. A decay

      * value of .5 means the echo heard is half as loud as the source.

      *

      * @param echoDelay the echoDelay

      * @param decay the decay

      */

     public EchoFilter( float echoDelay, float decay )

     {

         int numSampleDelay = ( Math.round( LuteceWordToSound.getSoundsSampleRate( ) * ( echoDelay / 1000 ) ) +

             1 );

         _delayBuffer = new short[numSampleDelay];

         _decay = decay / 100;

     }

     /**

      * Gets the remaining size, in bytes, of samples that this filter can echo

      * after the sound is done playing. Ensures that the sound will have decayed

      * to below 1% of maximum volume (amplitude).

      *

      * @return the Remaining Size

      */

     public int getRemainingSize(  )

     {

         float finalDecay = 0.01f;

         // derived from Math.pow(decay,x) <= finalDecay

         int numRemainingBuffers = (int) Math.ceil( Math.log( finalDecay ) / Math.log( _decay ) );

         int bufferSize = _delayBuffer.length;

         return bufferSize * numRemainingBuffers;

     }

     /**

      * Clears this EchoFilter's internal delay buffer.

      */

     public void reset(  )

     {

         for ( int i = 0; i < _delayBuffer.length; i++ )

         {

             _delayBuffer[i] = 0;

         }

         _delayBufferPos = 0;

     }

     /**

      * Filters the sound samples to add an echo. The samples played are added to

      * the sound in the delay buffer multipied by the decay rate. The result is

      * then stored in the delay buffer, so multiple echoes are heard.

      *

      * @param samples the samples

      * @param offset the offset

      * @param length the length

      * @param sampleSizeInBits the sample size in bits

      */

     public void filter( byte[] samples, int offset, int length, int sampleSizeInBits )

     {

         if ( sampleSizeInBits == SAMPLE_SIZE_8_BIT )

         {

             for ( int i = offset; i < ( offset + length ); i++ )

             {

                 // update the sample

                 short oldSample = get8bitSample( samples, i );

                 short newSample = (short) ( oldSample + ( _decay * _delayBuffer[_delayBufferPos] ) );

                 set8bitSample( samples, i, newSample );

                 // update the delay buffer

                 _delayBuffer[_delayBufferPos] = newSample;

                 _delayBufferPos++;

                 if ( _delayBufferPos == _delayBuffer.length )

                 {

                     _delayBufferPos = 0;

                 }

             }

         }

         else if ( sampleSizeInBits == SAMPLE_SIZE_16_BIT )

         {

             for ( int i = offset; i < ( offset + length ); i += 2 )

             {

                 // update the sample

                 short oldSample = get16bitSample( samples, i );

                 short newSample = (short) ( oldSample + ( _decay * _delayBuffer[_delayBufferPos] ) );

                 set16bitSample( samples, i, newSample );

                 // update the delay buffer

                 _delayBuffer[_delayBufferPos] = newSample;

                 _delayBufferPos++;

                 if ( _delayBufferPos == _delayBuffer.length )

                 {

                     _delayBufferPos = 0;

                 }

             }

         }

     }

 }