151 lines
4.4 KiB
Java
151 lines
4.4 KiB
Java
/*
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* Copyright (C) 2008 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.media;
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import java.io.InputStream;
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import java.io.IOException;
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/**
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* ResampleInputStream
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* @hide
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*/
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public final class ResampleInputStream extends InputStream
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{
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static {
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System.loadLibrary("media_jni");
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}
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private final static String TAG = "ResampleInputStream";
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// pcm input stream
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private InputStream mInputStream;
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// sample rates, assumed to be normalized
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private final int mRateIn;
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private final int mRateOut;
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// input pcm data
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private byte[] mBuf;
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private int mBufCount;
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// length of 2:1 fir
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private static final int mFirLength = 29;
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// helper for bytewise read()
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private final byte[] mOneByte = new byte[1];
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/**
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* Create a new ResampleInputStream, which converts the sample rate
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* @param inputStream InputStream containing 16 bit PCM.
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* @param rateIn the input sample rate.
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* @param rateOut the output sample rate.
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* This only handles rateIn == rateOut / 2 for the moment.
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*/
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public ResampleInputStream(InputStream inputStream, int rateIn, int rateOut) {
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// only support 2:1 at the moment
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if (rateIn != 2 * rateOut) throw new IllegalArgumentException("only support 2:1 at the moment");
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rateIn = 2;
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rateOut = 1;
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mInputStream = inputStream;
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mRateIn = rateIn;
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mRateOut = rateOut;
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}
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@Override
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public int read() throws IOException {
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int rtn = read(mOneByte, 0, 1);
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return rtn == 1 ? (0xff & mOneByte[0]) : -1;
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}
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@Override
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public int read(byte[] b) throws IOException {
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return read(b, 0, b.length);
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}
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@Override
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public int read(byte[] b, int offset, int length) throws IOException {
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if (mInputStream == null) throw new IllegalStateException("not open");
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// ensure that mBuf is big enough to cover requested 'length'
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int nIn = ((length / 2) * mRateIn / mRateOut + mFirLength) * 2;
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if (mBuf == null) {
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mBuf = new byte[nIn];
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} else if (nIn > mBuf.length) {
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byte[] bf = new byte[nIn];
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System.arraycopy(mBuf, 0, bf, 0, mBufCount);
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mBuf = bf;
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}
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// read until we have enough data for at least one output sample
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while (true) {
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int len = ((mBufCount / 2 - mFirLength) * mRateOut / mRateIn) * 2;
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if (len > 0) {
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length = len < length ? len : (length / 2) * 2;
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break;
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}
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// TODO: should mBuf.length below be nIn instead?
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int n = mInputStream.read(mBuf, mBufCount, mBuf.length - mBufCount);
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if (n == -1) return -1;
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mBufCount += n;
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}
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// resample input data
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fir21(mBuf, 0, b, offset, length / 2);
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// move any unused bytes to front of mBuf
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int nFwd = length * mRateIn / mRateOut;
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mBufCount -= nFwd;
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if (mBufCount > 0) System.arraycopy(mBuf, nFwd, mBuf, 0, mBufCount);
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return length;
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}
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/*
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@Override
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public int available() throws IOException {
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int nsamples = (mIn - mOut + mInputStream.available()) / 2;
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return ((nsamples - mFirLength) * mRateOut / mRateIn) * 2;
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}
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*/
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@Override
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public void close() throws IOException {
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try {
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if (mInputStream != null) mInputStream.close();
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} finally {
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mInputStream = null;
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}
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}
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@Override
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protected void finalize() throws Throwable {
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if (mInputStream != null) {
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close();
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throw new IllegalStateException("someone forgot to close ResampleInputStream");
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}
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}
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//
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// fir filter code JNI interface
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//
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private static native void fir21(byte[] in, int inOffset,
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byte[] out, int outOffset, int npoints);
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}
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