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 * {@link #error} can be called at any stage in the synthesis process to
26 * indicate that an error has occurred, but if the call is made after a call
27 * to {@link #done}, it might be discarded.
28 *
29 * {@link #done} must be called at the end of synthesis, regardless of errors.
30 *
31 * All methods can be only called on the synthesis thread.
32 */
33public interface SynthesisCallback {
34    /**
35     * @return the maximum number of bytes that the TTS engine can pass in a single call of
36     *         {@link #audioAvailable}. Calls to {@link #audioAvailable} with data lengths
37     *         larger than this 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}, {@link TextToSpeech#ERROR} or
53     *          {@link TextToSpeech#STOPPED}.
54     */
55    public int start(int sampleRateInHz, int audioFormat, int channelCount);
56
57    /**
58     * The service should call this method when synthesized audio is ready for consumption.
59     *
60     * This method should only be called on the synthesis thread,
61     * while in {@link TextToSpeechService#onSynthesizeText}.
62     *
63     * @param buffer The generated audio data. This method will not hold on to {@code buffer},
64     *         so the caller is free to modify it after this method returns.
65     * @param offset The offset into {@code buffer} where the audio data starts.
66     * @param length The number of bytes of audio data in {@code buffer}. This must be
67     *         less than or equal to the return value of {@link #getMaxBufferSize}.
68     * @return {@link TextToSpeech#SUCCESS}, {@link TextToSpeech#ERROR} or
69     *          {@link TextToSpeech#STOPPED}.
70     */
71    public int audioAvailable(byte[] buffer, int offset, int length);
72
73    /**
74     * The service should call this method when all the synthesized audio for a request has
75     * been passed to {@link #audioAvailable}.
76     *
77     * This method should only be called on the synthesis thread,
78     * while in {@link TextToSpeechService#onSynthesizeText}.
79     *
80     * This method has to be called if {@link #start} and/or {@link #error} was called.
81     *
82     * @return {@link TextToSpeech#SUCCESS}, {@link TextToSpeech#ERROR} or
83     *          {@link TextToSpeech#STOPPED}.
84     */
85    public int done();
86
87    /**
88     * The service should call this method if the speech synthesis fails.
89     *
90     * This method should only be called on the synthesis thread,
91     * while in {@link TextToSpeechService#onSynthesizeText}.
92     */
93    public void error();
94
95
96    /**
97     * The service should call this method if the speech synthesis fails.
98     *
99     * This method should only be called on the synthesis thread,
100     * while in {@link TextToSpeechService#onSynthesizeText}.
101     *
102     * @param errorCode Error code to pass to the client. One of the ERROR_ values from
103     *      {@link TextToSpeech}
104     */
105    public void error(int errorCode);
106
107    /**
108     * Check if {@link #start} was called or not.
109     *
110     * This method should only be called on the synthesis thread,
111     * while in {@link TextToSpeechService#onSynthesizeText}.
112     *
113     * Useful for checking if a fallback from network request is possible.
114     */
115    public boolean hasStarted();
116
117    /**
118     * Check if {@link #done} was called or not.
119     *
120     * This method should only be called on the synthesis thread,
121     * while in {@link TextToSpeechService#onSynthesizeText}.
122     *
123     * Useful for checking if a fallback from network request is possible.
124     */
125    public boolean hasFinished();
126}
127