1/*
2 * Copyright (C) 2006 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.speechrecorder;
18
19import java.io.IOException;
20import java.io.InputStream;
21
22import android.media.AudioRecord;
23
24import static android.media.AudioFormat.CHANNEL_IN_MONO;
25import static android.media.AudioFormat.ENCODING_PCM_16BIT;
26import static android.media.MediaRecorder.AudioSource.VOICE_RECOGNITION;
27
28/**
29 * Provides an InputStream like API over {@code android.media.AudioRecord}.
30 *
31 * <b>Not thread safe.</b>
32 */
33public final class MicrophoneInputStream extends InputStream {
34
35    private final int mSampleRate;
36    private final int mBufferSize;
37    private final AudioRecord mAudioRecord;
38
39    private boolean mRecording;
40
41    public MicrophoneInputStream(int sampleRate) throws IOException {
42        mSampleRate = sampleRate;
43        mBufferSize = AudioRecord.getMinBufferSize(sampleRate,
44            CHANNEL_IN_MONO, ENCODING_PCM_16BIT);
45        mAudioRecord = createAudioRecord();
46        mRecording = false;
47    }
48
49    private AudioRecord createAudioRecord() throws IOException {
50        AudioRecord ar = new AudioRecord(VOICE_RECOGNITION,
51            mSampleRate, CHANNEL_IN_MONO, ENCODING_PCM_16BIT, mBufferSize);
52
53        if (ar.getState() != AudioRecord.STATE_INITIALIZED) {
54            ar.release();
55            throw new IOException("Unable to create AudioRecord");
56        }
57
58        return ar;
59    }
60
61    private void maybeStartRecording() throws IOException {
62        if (mRecording) {
63            return;
64        }
65
66        mAudioRecord.startRecording();
67
68        int recordingState = mAudioRecord.getRecordingState();
69        if (recordingState != AudioRecord.RECORDSTATE_RECORDING) {
70            throw new IOException("Unexpected recordingState: " + recordingState);
71        }
72        mRecording = true;
73    }
74
75    @Override
76    public int read() throws IOException {
77        throw new UnsupportedOperationException("Single byte read.");
78    }
79
80    @Override
81    public int read(byte[] b, int offset, int length) throws IOException {
82        maybeStartRecording();
83
84        final int ret = mAudioRecord.read(b, offset, length);
85        if (ret == AudioRecord.ERROR_INVALID_OPERATION ||
86                ret == AudioRecord.ERROR_BAD_VALUE) {
87            throw new IOException("AudioRecord.read returned: " + ret);
88        }
89
90        return ret;
91    }
92
93    @Override
94    public void close() throws IOException {
95        mAudioRecord.stop();
96        mAudioRecord.release();
97    }
98}
99