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 * 26 * {@link #error} can be called at any stage in the synthesis process to 27 * indicate that an error has occurred, but if the call is made after a call 28 * to {@link #done}, it might be discarded. 29 */ 30 public interface SynthesisCallback { 31 /** 32 * @return the maximum number of bytes that the TTS engine can pass in a single call of 33 * {@link #audioAvailable}. Calls to {@link #audioAvailable} with data lengths 34 * larger than this value will not succeed. 35 */ getMaxBufferSize()36 public int getMaxBufferSize(); 37 38 /** 39 * The service should call this when it starts to synthesize audio for this 40 * request. 41 * 42 * This method should only be called on the synthesis thread, 43 * while in {@link TextToSpeechService#onSynthesizeText}. 44 * 45 * @param sampleRateInHz Sample rate in HZ of the generated audio. 46 * @param audioFormat Audio format of the generated audio. Must be one of 47 * the ENCODING_ constants defined in {@link android.media.AudioFormat}. 48 * @param channelCount The number of channels. Must be {@code 1} or {@code 2}. 49 * @return {@link TextToSpeech#SUCCESS} or {@link TextToSpeech#ERROR}. 50 */ start(int sampleRateInHz, int audioFormat, int channelCount)51 public int start(int sampleRateInHz, int audioFormat, int channelCount); 52 53 /** 54 * The service should call this method when synthesized audio is ready for consumption. 55 * 56 * This method should only be called on the synthesis thread, 57 * while in {@link TextToSpeechService#onSynthesizeText}. 58 * 59 * @param buffer The generated audio data. This method will not hold on to {@code buffer}, 60 * so the caller is free to modify it after this method returns. 61 * @param offset The offset into {@code buffer} where the audio data starts. 62 * @param length The number of bytes of audio data in {@code buffer}. This must be 63 * less than or equal to the return value of {@link #getMaxBufferSize}. 64 * @return {@link TextToSpeech#SUCCESS} or {@link TextToSpeech#ERROR}. 65 */ audioAvailable(byte[] buffer, int offset, int length)66 public int audioAvailable(byte[] buffer, int offset, int length); 67 68 /** 69 * The service should call this method when all the synthesized audio for a request has 70 * been passed to {@link #audioAvailable}. 71 * 72 * This method should only be called on the synthesis thread, 73 * while in {@link TextToSpeechService#onSynthesizeText}. 74 * 75 * @return {@link TextToSpeech#SUCCESS} or {@link TextToSpeech#ERROR}. 76 */ done()77 public int done(); 78 79 /** 80 * The service should call this method if the speech synthesis fails. 81 * 82 * This method should only be called on the synthesis thread, 83 * while in {@link TextToSpeechService#onSynthesizeText}. 84 */ error()85 public void error(); 86 87 }