PCM Waveファイル - ステレオからモノラル

Question

私はステレオであるオーディオファイルを持っています。他のすべてのバイト（ヘッダーの後）をスキップする場合にモノに変換していますか？ 16ビットの署名付きPCM形式でエンコードされています。私はjavax.sound.sampledが利用可能です。ここで

は動作しませんでした、私が試したコードです：

WaveFileWriter wfw = new WaveFileWriter(); 
AudioFormat format = new AudioFormat(Encoding.PCM_SIGNED, 44100, 16, 2, 2, 44100, false); 
AudioFormat monoFormat = new AudioFormat(Encoding.PCM_SIGNED, 44100, 16, 1, 2, 44100, false); 

byte[] audioData = dataout.toByteArray(); 
int length = audioData.length; 
ByteArrayInputStream bais = new ByteArrayInputStream(audioData); 

AudioInputStream stereoStream = new AudioInputStream(bais,format,length); 
AudioInputStream monoStream = new AudioInputStream(stereoStream,format,length/2); 

wfw.write(monoStream, Type.WAVE, new File(Environment. 
       getExternalStorageDirectory().getAbsolutePath()+"/stegDroid/un-ogged.wav")); 

このコードは、PCMデータに変換するJorbisを使用して.oggファイルを読み込んだ後に使用されます。唯一の問題は結果がステレオでモノラルである必要があるため、別の解決策があればそれを聞いて嬉しいです！

Answer 1

私はステレオのオーディオファイルを持っています。 モノラルに変換していますか 他のすべてのバイトをスキップしています（ ヘッダーの後）？

ほとんど - あなたは他のすべてのサンプル、ないバイトをスキップしたいです。あなたの場合は、各サンプルのサイズが16ビット= 2バイトであるように見えます。したがって、2バイトをスキップし、2バイトをスキップし、2バイトを取るなどしたいと考えています。

AudioInputStream monoStream = new AudioInputStream(stereoStream,format,length/2); 

wfw.write(monoStream, Type.WAVE, new File(Environment.getExternalStorageDirectory().getAbsolutePath()+"/stegDroid/un-ogged.wav")); 

あなただけの代わりに、他のすべてのサンプルを書き出すファイルの最初の半分を書き出すようにこれが見えます。また、単一のチャンネルを指定するには、WAVヘッダーを修正する必要があります（monoFormat参照）。

Answer 2

このコードを見てください。私がwavファイルのバイトを混乱させる必要があるとき、それは私を助けました。

 

package GlobalUtilities; 

import java.applet.Applet; 
import java.applet.AudioClip; 
import java.net.URISyntaxException; 
import java.util.logging.Level; 
import java.util.logging.Logger; 
import java.io.*; 
import java.io.File; 
import java.net.MalformedURLException; 
import java.net.URL; 
import javax.sound.sampled.*; 

/** 
* This class handles the reading, writing, and playing of wav files. It is 
* also capable of converting the file to its raw byte [] form. 
* 
* based on code by Evan Merz modified by Dan Vargo 
* @author dvargo 
*/ 
public class Wav { 
    /* 
    WAV File Specification 
    FROM http://ccrma.stanford.edu/courses/422/projects/WaveFormat/ 
    The canonical WAVE format starts with the RIFF header: 
    0   4 ChunkID   Contains the letters "RIFF" in ASCII form 
    (0x52494646 big-endian form). 
    4   4 ChunkSize  36 + SubChunk2Size, or more precisely: 
    4 + (8 + SubChunk1Size) + (8 + SubChunk2Size) 
    This is the size of the rest of the chunk 
    following this number. This is the size of the 
    entire file in bytes minus 8 bytes for the 
    two fields not included in this count: 
    ChunkID and ChunkSize. 
    8   4 Format   Contains the letters "WAVE" 
    (0x57415645 big-endian form). 

    The "WAVE" format consists of two subchunks: "fmt " and "data": 
    The "fmt " subchunk describes the sound data's format: 
    12  4 Subchunk1ID  Contains the letters "fmt " 
    (0x666d7420 big-endian form). 
    16  4 Subchunk1Size 16 for PCM. This is the size of the 
    rest of the Subchunk which follows this number. 
    20  2 AudioFormat  PCM = 1 (i.e. Linear quantization) 
    Values other than 1 indicate some 
    form of compression. 
    22  2 NumChannels  Mono = 1, Stereo = 2, etc. 
    24  4 SampleRate  8000, 44100, etc. 
    28  4 ByteRate   == SampleRate * NumChannels * BitsPerSample/8 
    32  2 BlockAlign  == NumChannels * BitsPerSample/8 
    The number of bytes for one sample including 
    all channels. I wonder what happens when 
    this number isn't an integer? 
    34  2 BitsPerSample 8 bits = 8, 16 bits = 16, etc. 

    The "data" subchunk contains the size of the data and the actual sound: 
    36  4 Subchunk2ID  Contains the letters "data" 
    (0x64617461 big-endian form). 
    40  4 Subchunk2Size == NumSamples * NumChannels * BitsPerSample/8 
    This is the number of bytes in the data. 
    You can also think of this as the size 
    of the read of the subchunk following this 
    number. 
    44  * Data    The actual sound data. 


    The thing that makes reading wav files tricky is that java has no unsigned types. This means that the 
    binary data can't just be read and cast appropriately. Also, we have to use larger types 
    than are normally necessary. 

    In many languages including java, an integer is represented by 4 bytes. The issue here is 
    that in most languages, integers can be signed or unsigned, and in wav files the integers 
    are unsigned. So, to make sure that we can store the proper values, we have to use longs 
    to hold integers, and integers to hold shorts. 

    Then, we have to convert back when we want to save our wav data. 

    It's complicated, but ultimately, it just results in a few extra functions at the bottom of 
    this file. Once you understand the issue, there is no reason to pay any more attention 
    to it. 

    ALSO: 

    This code won't read ALL wav files. This does not use to full specification. It just uses 
    a trimmed down version that most wav files adhere to. 

    */ 

    ByteArrayOutputStream byteArrayOutputStream; 
    AudioFormat audioFormat; 
    TargetDataLine targetDataLine; 
    AudioInputStream audioInputStream; 
    SourceDataLine sourceDataLine; 
    float frequency = 8000.0F; //8000,11025,16000,22050,44100 
    int samplesize = 16; 
    private String myPath; 
    private long myChunkSize; 
    private long mySubChunk1Size; 
    private int myFormat; 
    private long myChannels; 
    private long mySampleRate; 
    private long myByteRate; 
    private int myBlockAlign; 
    private int myBitsPerSample; 
    private long myDataSize; 
    // I made this public so that you can toss whatever you want in here 
    // maybe a recorded buffer, maybe just whatever you want 
    public byte[] myData; 



    public Wav() 
    { 
     myPath = ""; 
    } 

    // constructor takes a wav path 
    public Wav(String tmpPath) { 
     myPath = tmpPath; 
    } 


    // get/set for the Path property 
    public String getPath() 
    { 
     return myPath; 
    } 

    public void setPath(String newPath) 
    { 
     myPath = newPath; 
    } 

    // read a wav file into this class 
    public boolean read() { 
     DataInputStream inFile = null; 
     myData = null; 
     byte[] tmpLong = new byte[4]; 
     byte[] tmpInt = new byte[2]; 

     try { 
      inFile = new DataInputStream(new FileInputStream(myPath)); 

      //System.out.println("Reading wav file...\n"); // for debugging only 

      String chunkID = "" + (char) inFile.readByte() + (char) inFile.readByte() + (char) inFile.readByte() + (char) inFile.readByte(); 

      inFile.read(tmpLong); // read the ChunkSize 
      myChunkSize = byteArrayToLong(tmpLong); 

      String format = "" + (char) inFile.readByte() + (char) inFile.readByte() + (char) inFile.readByte() + (char) inFile.readByte(); 

      // print what we've read so far 
      //System.out.println("chunkID:" + chunkID + " chunk1Size:" + myChunkSize + " format:" + format); // for debugging only 



      String subChunk1ID = "" + (char) inFile.readByte() + (char) inFile.readByte() + (char) inFile.readByte() + (char) inFile.readByte(); 

      inFile.read(tmpLong); // read the SubChunk1Size 
      mySubChunk1Size = byteArrayToLong(tmpLong); 

      inFile.read(tmpInt); // read the audio format. This should be 1 for PCM 
      myFormat = byteArrayToInt(tmpInt); 

      inFile.read(tmpInt); // read the # of channels (1 or 2) 
      myChannels = byteArrayToInt(tmpInt); 

      inFile.read(tmpLong); // read the samplerate 
      mySampleRate = byteArrayToLong(tmpLong); 

      inFile.read(tmpLong); // read the byterate 
      myByteRate = byteArrayToLong(tmpLong); 

      inFile.read(tmpInt); // read the blockalign 
      myBlockAlign = byteArrayToInt(tmpInt); 

      inFile.read(tmpInt); // read the bitspersample 
      myBitsPerSample = byteArrayToInt(tmpInt); 

      // print what we've read so far 
      //System.out.println("SubChunk1ID:" + subChunk1ID + " SubChunk1Size:" + mySubChunk1Size + " AudioFormat:" + myFormat + " Channels:" + myChannels + " SampleRate:" + mySampleRate); 


      // read the data chunk header - reading this IS necessary, because not all wav files will have the data chunk here - for now, we're just assuming that the data chunk is here 
      String dataChunkID = "" + (char) inFile.readByte() + (char) inFile.readByte() + (char) inFile.readByte() + (char) inFile.readByte(); 

      inFile.read(tmpLong); // read the size of the data 
      myDataSize = byteArrayToLong(tmpLong); 


      // read the data chunk 
      myData = new byte[(int) myDataSize]; 
      inFile.read(myData); 

      // close the input stream 
      inFile.close(); 
     } catch (Exception e) { 
      return false; 
     } 

     return true; // this should probably be something more descriptive 
    } 

    // write out the wav file 
    public boolean save() { 
     try { 
      DataOutputStream outFile = new DataOutputStream(new FileOutputStream(myPath + "temp")); 

      // write the wav file per the wav file format 
      outFile.writeBytes("RIFF");     // 00 - RIFF 
      outFile.write(intToByteArray((int) myChunkSize), 0, 4);  // 04 - how big is the rest of this file? 
      outFile.writeBytes("WAVE");     // 08 - WAVE 
      outFile.writeBytes("fmt ");     // 12 - fmt 
      outFile.write(intToByteArray((int) mySubChunk1Size), 0, 4); // 16 - size of this chunk 
      outFile.write(shortToByteArray((short) myFormat), 0, 2);  // 20 - what is the audio format? 1 for PCM = Pulse Code Modulation 
      outFile.write(shortToByteArray((short) myChannels), 0, 2); // 22 - mono or stereo? 1 or 2? (or 5 or ???) 
      outFile.write(intToByteArray((int) mySampleRate), 0, 4);  // 24 - samples per second (numbers per second) 
      outFile.write(intToByteArray((int) myByteRate), 0, 4);  // 28 - bytes per second 
      outFile.write(shortToByteArray((short) myBlockAlign), 0, 2); // 32 - # of bytes in one sample, for all channels 
      outFile.write(shortToByteArray((short) myBitsPerSample), 0, 2); // 34 - how many bits in a sample(number)? usually 16 or 24 
      outFile.writeBytes("data");     // 36 - data 
      outFile.write(intToByteArray((int) myDataSize), 0, 4);  // 40 - how big is this data chunk 
      outFile.write(myData);      // 44 - the actual data itself - just a long string of numbers 
     } catch (Exception e) { 
      System.out.println(e.getMessage()); 
      return false; 
     } 

     return true; 
    } 

    // return a printable summary of the wav file 
    public String getSummary() { 
     //String newline = System.getProperty("line.separator"); 
     String newline = "
"; 
     String summary = "Format: " + myFormat + newline + "Channels: " + myChannels + newline + "SampleRate: " + mySampleRate + newline + "ByteRate: " + myByteRate + newline + "BlockAlign: " + myBlockAlign + newline + "BitsPerSample: " + myBitsPerSample + newline + "DataSize: " + myDataSize + ""; 
     return summary; 
    } 

    public byte[] getBytes() { 
     read(); 
     return myData; 
    } 



    /** 
    * Plays back audio stored in the byte array using an audio format given by 
    * freq, sample rate, ect. 
    * @param data The byte array to play 
    */ 
    public void playAudio(byte[] data) { 
     try { 
      byte audioData[] = data; 
      //Get an input stream on the byte array containing the data 
      InputStream byteArrayInputStream = new ByteArrayInputStream(audioData); 
      AudioFormat audioFormat = getAudioFormat(); 
      audioInputStream = new AudioInputStream(byteArrayInputStream, audioFormat, audioData.length/audioFormat.getFrameSize()); 
      DataLine.Info dataLineInfo = new DataLine.Info(SourceDataLine.class, audioFormat); 
      sourceDataLine = (SourceDataLine) AudioSystem.getLine(dataLineInfo); 
      sourceDataLine.open(audioFormat); 
      sourceDataLine.start(); 

      //Create a thread to play back the data and start it running. It will run \ 
      //until all the data has been played back. 
      Thread playThread = new Thread(new PlayThread()); 
      playThread.start(); 
     } catch (Exception e) { 
      System.out.println(e); 
     } 
    } 

    /** 
    * This method creates and returns an AudioFormat object for a given set 
    * of format parameters. If these parameters don't work well for 
    * you, try some of the other allowable parameter values, which 
    * are shown in comments following the declarations. 
    * @return 
    */ 
    private AudioFormat getAudioFormat() { 
     float sampleRate = frequency; 
     //8000,11025,16000,22050,44100 
     int sampleSizeInBits = samplesize; 
     //8,16 
     int channels = 1; 
     //1,2 
     boolean signed = true; 
     //true,false 
     boolean bigEndian = false; 
     //true,false 
     //return new AudioFormat(AudioFormat.Encoding.PCM_SIGNED, 8000.0f, 8, 1, 1, 
     //8000.0f, false); 

     return new AudioFormat(sampleRate, sampleSizeInBits, channels, signed, bigEndian); 
    } 

    public void playWav(String filePath) { 
     try { 
      AudioClip clip = (AudioClip) Applet.newAudioClip(new File(filePath).toURI().toURL()); 
      clip.play(); 
     } catch (Exception e) { 
      Logger.getLogger(Wav.class.getName()).log(Level.SEVERE, null, e); 
     } 

    } 

// =========================== 
// CONVERT BYTES TO JAVA TYPES 
// =========================== 
    // these two routines convert a byte array to a unsigned short 
    public static int byteArrayToInt(byte[] b) { 
     int start = 0; 
     int low = b[start] & 0xff; 
     int high = b[start + 1] & 0xff; 
     return (int) (high > 8) & 0x000000FF); 
     b[2] = (byte) ((i >> 16) & 0x000000FF); 
     b[3] = (byte) ((i >> 24) & 0x000000FF); 
     return b; 
    } 

    // convert a short to a byte array 
    public static byte[] shortToByteArray(short data) { 
     return new byte[]{(byte) (data & 0xff), (byte) ((data >>> 8) & 0xff)}; 
    } 

    /** 
    * Inner class to play back the data that was saved 
    */ 
    class PlayThread extends Thread { 

     byte tempBuffer[] = new byte[10000]; 

     public void run() { 
      try { 
       int cnt; 
       //Keep looping until the input 
       // read method returns -1 for 
       // empty stream. 
       while ((cnt = audioInputStream.read(tempBuffer, 0, tempBuffer.length)) != -1) { 
        if (cnt > 0) { 
         //Write data to the internal 
         // buffer of the data line 
         // where it will be delivered 
         // to the speaker. 
         sourceDataLine.write(tempBuffer, 0, cnt); 
        } 
       } 
       //Block and wait for internal 
       // buffer of the data line to 
       // empty. 
       sourceDataLine.drain(); 
       sourceDataLine.close(); 
      } catch (Exception e) { 
       System.out.println(e); 
       System.exit(0); 
      } 
     } 
    } 
}