| /* |
| * 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); |
| |
| } |