core/java/android/speech/srec/MicrophoneInputStream.java

/*---------------------------------------------------------------------------*
 *  MicrophoneInputStream.java                                               *
 *                                                                           *
 *  Copyright 2007 Nuance Communciations, Inc.                               *
 *                                                                           *
 *  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.speech.srec;

import java.io.IOException;
import java.io.InputStream;
import java.lang.IllegalStateException;


/**
 * PCM input stream from the microphone, 16 bits per sample.
 */
public final class MicrophoneInputStream extends InputStream {
    static {
        System.loadLibrary("srec_jni");
    }
    
    private final static String TAG = "MicrophoneInputStream";
    private long mAudioRecord = 0;
    private byte[] mOneByte = new byte[1];
    
    /**
     * MicrophoneInputStream constructor.
     * @param sampleRate sample rate of the microphone, typically 11025 or 8000.
     * @param fifoDepth depth of the real time fifo, measured in sampleRate clock ticks.
     * This determines how long an application may delay before losing data.
     */
    public MicrophoneInputStream(int sampleRate, int fifoDepth) throws IOException {
        mAudioRecord = AudioRecordNew(sampleRate, fifoDepth);
        if (mAudioRecord == 0) throw new IOException("AudioRecord constructor failed - busy?");
        int status = AudioRecordStart(mAudioRecord);
        if (status != 0) {
            close();
            throw new IOException("AudioRecord start failed: " + status);
        }
    }

    @Override
    public int read() throws IOException {
        if (mAudioRecord == 0) throw new IllegalStateException("not open");
        int rtn = AudioRecordRead(mAudioRecord, mOneByte, 0, 1);
        return rtn == 1 ? ((int)mOneByte[0] & 0xff) : -1;
    }

    @Override
    public int read(byte[] b) throws IOException {
        if (mAudioRecord == 0) throw new IllegalStateException("not open");
        return AudioRecordRead(mAudioRecord, b, 0, b.length);
    }
    
    @Override
    public int read(byte[] b, int offset, int length) throws IOException {
        if (mAudioRecord == 0) throw new IllegalStateException("not open");
        // TODO: should we force all reads to be a multiple of the sample size?
        return AudioRecordRead(mAudioRecord, b, offset, length);
    }
    
    /**
     * Closes this stream.
     */
    @Override
    public void close() throws IOException {
        if (mAudioRecord != 0) {
            try {
                AudioRecordStop(mAudioRecord);
            } finally {
                try {
                    AudioRecordDelete(mAudioRecord);
                } finally {
                    mAudioRecord = 0;
                }
            }
        }
    }
    
    @Override
    protected void finalize() throws Throwable {
        if (mAudioRecord != 0) {
            close();
            throw new IOException("someone forgot to close MicrophoneInputStream");
        }
    }
    
    //
    // AudioRecord JNI interface
    //
    private static native long AudioRecordNew(int sampleRate, int fifoDepth);
    private static native int AudioRecordStart(long audioRecord);
    private static native int AudioRecordRead(long audioRecord, byte[] b, int offset, int length) throws IOException;
    private static native void AudioRecordStop(long audioRecord) throws IOException;
    private static native void AudioRecordDelete(long audioRecord) throws IOException;
}