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Android example source code file (ResampleInputStream.java)

This example Android source code file (ResampleInputStream.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Android by Example" TM.

Java - Android tags/keywords

android, illegalargumentexception, illegalstateexception, inputstream, io, ioexception, override, resampleinputstream, string, tag, throwable, util, utilities, utils

The ResampleInputStream.java Android example source code

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.media;

import android.util.Config;
import android.util.Log;

import java.io.InputStream;
import java.io.IOException;


/**
 * ResampleInputStream
 * @hide
 */
public final class ResampleInputStream extends InputStream
{    
    static {
        System.loadLibrary("media_jni");
    }
    
    private final static String TAG = "ResampleInputStream";
    
    // pcm input stream
    private InputStream mInputStream;

    // sample rates, assumed to be normalized
    private final int mRateIn;
    private final int mRateOut;
    
    // input pcm data
    private byte[] mBuf;
    private int mBufCount;
    
    // length of 2:1 fir
    private static final int mFirLength = 29;
    
    // helper for bytewise read()
    private final byte[] mOneByte = new byte[1];
    
    /**
     * 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.
     */
    public ResampleInputStream(InputStream inputStream, int rateIn, int rateOut) {
        // 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;
    }

    @Override
    public int read() throws IOException {
        int rtn = read(mOneByte, 0, 1);
        return rtn == 1 ? (0xff & mOneByte[0]) : -1;
    }
    
    @Override
    public int read(byte[] b) throws IOException {
        return read(b, 0, b.length);
    }

    @Override
    public int read(byte[] b, int offset, int length) throws IOException {
        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;
    }

/*
    @Override
    public int available() throws IOException {
        int nsamples = (mIn - mOut + mInputStream.available()) / 2;
        return ((nsamples - mFirLength) * mRateOut / mRateIn) * 2;
    }
*/

    @Override
    public void close() throws IOException {
        try {
            if (mInputStream != null) mInputStream.close();
        } finally {
            mInputStream = null;
        }
    }

    @Override
    protected void finalize() throws Throwable {
        if (mInputStream != null) {
            close();
            throw new IllegalStateException("someone forgot to close ResampleInputStream");
        }
    }

    //
    // fir filter code JNI interface
    //
    private static native void fir21(byte[] in, int inOffset,
            byte[] out, int outOffset, int npoints);

}

Other Android examples (source code examples)

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