SynthesisCallback.java revision e22b69a7de0349b99d3107349d1d3aa72d62c841 
1/*
2 * Copyright (C) 2011 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
5 * use this file except in compliance with the License. You may obtain a copy of
6 * 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, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations under
14 * the License.
15 */
16package android.speech.tts;
17
18/**
19 * A callback to return speech data synthesized by a text to speech engine.
20 *
21 * The engine can provide streaming audio by calling
22 * {@link #start}, then {@link #audioAvailable} until all audio has been provided, then finally
23 * {@link #done}.
24 *
25 * Alternatively, the engine can provide all the audio at once, by using
26 * {@link #completeAudioAvailable}.
27 *
28 * {@link #error} can be called at any stage in the synthesis process to
29 * indicate that an error has occured, but if the call is made after a call
30 * to {@link #done} or {@link #completeAudioAvailable} it might be discarded.
31 */
32public interface SynthesisCallback {
33    /**
34     * @return the maximum number of bytes that the TTS engine can pass in a single call of
35     *         {@link #audioAvailable}. This does not apply to {@link #completeAudioAvailable}.
36     *         Calls to {@link #audioAvailable} with data lengths larger than this
37     *         value will not succeed.
38     */
39    public int getMaxBufferSize();
40
41    /**
42     * The service should call this when it starts to synthesize audio for this
43     * request.
44     *
45     * This method should only be called on the synthesis thread,
46     * while in {@link TextToSpeechService#onSynthesizeText}.
47     *
48     * @param sampleRateInHz Sample rate in HZ of the generated audio.
49     * @param audioFormat Audio format of the generated audio. Must be one of
50     *         the ENCODING_ constants defined in {@link android.media.AudioFormat}.
51     * @param channelCount The number of channels. Must be {@code 1} or {@code 2}.
52     * @return {@link TextToSpeech#SUCCESS} or {@link TextToSpeech#ERROR}.
53     */
54    public int start(int sampleRateInHz, int audioFormat, int channelCount);
55
56    /**
57     * The service should call this method when synthesized audio is ready for consumption.
58     *
59     * This method should only be called on the synthesis thread,
60     * while in {@link TextToSpeechService#onSynthesizeText}.
61     *
62     * @param buffer The generated audio data. This method will not hold on to {@code buffer},
63     *         so the caller is free to modify it after this method returns.
64     * @param offset The offset into {@code buffer} where the audio data starts.
65     * @param length The number of bytes of audio data in {@code buffer}. This must be
66     *         less than or equal to the return value of {@link #getMaxBufferSize}.
67     * @return {@link TextToSpeech#SUCCESS} or {@link TextToSpeech#ERROR}.
68     */
69    public int audioAvailable(byte[] buffer, int offset, int length);
70
71    /**
72     * The service can call this method instead of using {@link #start}, {@link #audioAvailable}
73     * and {@link #done} if all the audio data is available in a single buffer.
74     *
75     * @param sampleRateInHz Sample rate in HZ of the generated audio.
76     * @param audioFormat Audio format of the generated audio. Must be one of
77     *         the ENCODING_ constants defined in {@link android.media.AudioFormat}.
78     * @param channelCount The number of channels. Must be {@code 1} or {@code 2}.
79     * @param buffer The generated audio data. This method will not hold on to {@code buffer},
80     *         so the caller is free to modify it after this method returns.
81     * @param offset The offset into {@code buffer} where the audio data starts.
82     * @param length The number of bytes of audio data in {@code buffer}.
83     * @return {@link TextToSpeech#SUCCESS} or {@link TextToSpeech#ERROR}.
84     */
85    public int completeAudioAvailable(int sampleRateInHz, int audioFormat,
86            int channelCount, byte[] buffer, int offset, int length);
87
88    /**
89     * The service should call this method when all the synthesized audio for a request has
90     * been passed to {@link #audioAvailable}.
91     *
92     * This method should only be called on the synthesis thread,
93     * while in {@link TextToSpeechService#onSynthesizeText}.
94     *
95     * @return {@link TextToSpeech#SUCCESS} or {@link TextToSpeech#ERROR}.
96     */
97    public int done();
98
99    /**
100     * The service should call this method if the speech synthesis fails.
101     *
102     * This method should only be called on the synthesis thread,
103     * while in {@link TextToSpeechService#onSynthesizeText}.
104     */
105    public void error();
106
107}