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ResampleInputStream.javaAPI DocAndroid 1.5 API4565Wed May 06 22:42:00 BST 2009android.media

ResampleInputStream

public final class ResampleInputStream extends InputStream
ResampleInputStream
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Fields Summary
private static final String
TAG
private InputStream
mInputStream
private final int
mRateIn
private final int
mRateOut
private byte[]
mBuf
private int
mBufCount
private static final int
mFirLength
private final byte[]
mOneByte
Constructors Summary
public ResampleInputStream(InputStream inputStream, int rateIn, int rateOut)
Create a new ResampleInputStream, which converts the sample rate

param
inputStream InputStream containing 16 bit PCM.
param
rateIn the input sample rate.
param
rateOut the output sample rate. This only handles rateIn == rateOut / 2 for the moment.

    
                                                
           
        // only support 2:1 at the moment
        if (rateIn != 2 * rateOut) throw new IllegalArgumentException("only support 2:1 at the moment");
        rateIn = 2;
        rateOut = 1;

        mInputStream = inputStream;
        mRateIn = rateIn;
        mRateOut = rateOut;
Methods Summary
public voidclose()

        try {
            if (mInputStream != null) mInputStream.close();
        } finally {
            mInputStream = null;
        }
protected voidfinalize()

        if (mInputStream != null) {
            close();
            throw new IllegalStateException("someone forgot to close ResampleInputStream");
        }
private static native voidfir21(byte[] in, int inOffset, byte[] out, int outOffset, int npoints)

public intread()
        int rtn = read(mOneByte, 0, 1);
        return rtn == 1 ? (0xff & mOneByte[0]) : -1;
    
public intread(byte[] b)
        return read(b, 0, b.length);
    
public intread(byte[] b, int offset, int length)
        if (mInputStream == null) throw new IllegalStateException("not open");

        // ensure that mBuf is big enough to cover requested 'length'
        int nIn = ((length / 2) * mRateIn / mRateOut + mFirLength) * 2;
        if (mBuf == null) {
            mBuf = new byte[nIn];
        } else if (nIn > mBuf.length) {
            byte[] bf = new byte[nIn];
            System.arraycopy(mBuf, 0, bf, 0, mBufCount);
            mBuf = bf;
        }
        
        // read until we have enough data for at least one output sample
        while (true) {
            int len = ((mBufCount / 2 - mFirLength) * mRateOut / mRateIn) * 2;
            if (len > 0) {
                length = len < length ? len : (length / 2) * 2;
                break;
            }
            // TODO: should mBuf.length below be nIn instead?
            int n = mInputStream.read(mBuf, mBufCount, mBuf.length - mBufCount);
            if (n == -1) return -1;
            mBufCount += n;
        }

        // resample input data
        fir21(mBuf, 0, b, offset, length / 2);
        
        // move any unused bytes to front of mBuf
        int nFwd = length * mRateIn / mRateOut;
        mBufCount -= nFwd;
        if (mBufCount > 0) System.arraycopy(mBuf, nFwd, mBuf, 0, mBufCount);
        
        return length;