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 */ 16 package 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 */ 33 public 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