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/*
* 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 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);
}
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