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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 
     18 package android.media.videoeditor;
     19 
     20 import java.io.File;
     21 import java.io.FileInputStream;
     22 import java.io.IOException;
     23 
     24 /**
     25  * Class which describes the waveform data of an audio track. The gain values
     26  * represent the average gain for an audio frame. For audio codecs which do not
     27  * operate on a per frame bases (eg. ALAW, ULAW) a reasonable audio frame
     28  * duration will be assumed (eg. 50ms).
     29  * {@hide}
     30  */
     31 public class WaveformData {
     32     /*
     33      *  Instance variables
     34      */
     35     private final int mFrameDurationMs;
     36     private final int mFramesCount;
     37     private final short[] mGains;
     38 
     39     /*
     40      * This constructor shall not be used
     41      */
     42     @SuppressWarnings("unused")
     43     private WaveformData() throws IOException {
     44         mFrameDurationMs = 0;
     45         mFramesCount = 0;
     46         mGains = null;
     47     }
     48 
     49     /*
     50      * Constructor
     51      *
     52      * @param audioWaveformFilename The name of the audio waveform file
     53      *
     54      * The file format is as following:
     55      * <ul>
     56      *  <li>first 4 bytes provide the number of samples for each value, as
     57      *  big-endian signed</li>
     58      *  <li>4 following bytes is the total number of values in the file, as
     59      *  big-endian signed</li>
     60      *  <li>then, all values follow as bytes</li>
     61      * </ul>
     62      *
     63      * @throws IOException on failure of file input stream operations
     64      * @throws IllegalArgumentException if audioWaveformFilename is null
     65      */
     66     WaveformData(String audioWaveformFilename) throws IOException {
     67 
     68         if (audioWaveformFilename == null) {
     69             throw new IllegalArgumentException("WaveformData : filename is null");
     70         }
     71 
     72         FileInputStream audioGraphFileReadHandle = null;
     73 
     74         try {
     75             final File audioGraphFileContext = new File(audioWaveformFilename);
     76 
     77             audioGraphFileReadHandle = new FileInputStream(audioGraphFileContext);
     78             /*
     79              * Read frame duration
     80              */
     81             final byte tempFrameDuration[] = new byte[4];
     82 
     83             audioGraphFileReadHandle.read(tempFrameDuration, 0, 4);
     84 
     85             int tempFrameDurationMs = 0;
     86             int tempFramesCounter = 0;
     87             for (int i = 0; i < 4; i++) {
     88                 tempFrameDurationMs = (tempFrameDurationMs << 8);
     89                 tempFrameDurationMs = (tempFrameDurationMs | (tempFrameDuration[i] & 0xff));
     90             }
     91             mFrameDurationMs = tempFrameDurationMs;
     92 
     93             /*
     94              * Read count
     95              */
     96             final byte tempFramesCount[] = new byte[4];
     97 
     98             audioGraphFileReadHandle.read(tempFramesCount, 0, 4);
     99             for (int i = 0; i < 4; i++) {
    100                 tempFramesCounter = (tempFramesCounter << 8);
    101                 tempFramesCounter = (tempFramesCounter | (tempFramesCount[i] & 0xff));
    102             }
    103             mFramesCount = tempFramesCounter;
    104 
    105             /*
    106              *  Capture the graph values
    107              */
    108             mGains = new short[mFramesCount];
    109 
    110             for (int i = 0; i < mFramesCount; i++) {
    111                 mGains[i] = (short)audioGraphFileReadHandle.read();
    112             }
    113         } finally {
    114             if (audioGraphFileReadHandle != null) {
    115                 audioGraphFileReadHandle.close();
    116             }
    117         }
    118     }
    119 
    120     /**
    121      * @return The duration of a frame in milliseconds
    122      */
    123     public int getFrameDuration() {
    124         return mFrameDurationMs;
    125     }
    126 
    127     /**
    128      * @return The number of frames within the waveform data
    129      */
    130     public int getFramesCount() {
    131         return mFramesCount;
    132     }
    133 
    134     /**
    135      * @return The array of frame gains. The size of the array is the frames
    136      *         count. The values of the frame gains range from 0 to 255.
    137      */
    138     public short[] getFrameGains() {
    139         return mGains;
    140     }
    141 }
    142