// Copyright 2016 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

syntax = "proto3";

package google.cloud.speech.v1beta1;

import "google/api/annotations.proto";
import "google/longrunning/operations.proto";
import "google/rpc/status.proto";

option java_multiple_files = true;
option java_outer_classname = "SpeechProto";
option java_package = "com.google.cloud.speech.v1beta1";


// Service that implements Google Cloud Speech API.
service Speech {
  // Perform synchronous speech-recognition: receive results after all audio
  // has been sent and processed.
  rpc SyncRecognize(SyncRecognizeRequest) returns (SyncRecognizeResponse) {
    option (google.api.http) = { post: "/v1beta1/speech:syncrecognize" body: "*" };
  }

  // Perform asynchronous speech-recognition: receive results via the
  // google.longrunning.Operations interface. `Operation.response` returns
  // `AsyncRecognizeResponse`.
  rpc AsyncRecognize(AsyncRecognizeRequest) returns (google.longrunning.Operation) {
    option (google.api.http) = { post: "/v1beta1/speech:asyncrecognize" body: "*" };
  }

  // Perform bidirectional streaming speech-recognition: receive results while
  // sending audio. This method is only available via the gRPC API (not REST).
  rpc StreamingRecognize(stream StreamingRecognizeRequest) returns (stream StreamingRecognizeResponse);
}

// `SyncRecognizeRequest` is the top-level message sent by the client for
// the `SyncRecognize` method.
message SyncRecognizeRequest {
  // [Required] The `config` message provides information to the recognizer
  // that specifies how to process the request.
  RecognitionConfig config = 1;

  // [Required] The audio data to be recognized.
  RecognitionAudio audio = 2;
}

// `AsyncRecognizeRequest` is the top-level message sent by the client for
// the `AsyncRecognize` method.
message AsyncRecognizeRequest {
  // [Required] The `config` message provides information to the recognizer
  // that specifies how to process the request.
  RecognitionConfig config = 1;

  // [Required] The audio data to be recognized.
  RecognitionAudio audio = 2;
}

// `StreamingRecognizeRequest` is the top-level message sent by the client for
// the `StreamingRecognize`. Multiple `StreamingRecognizeRequest` messages are
// sent. The first message must contain a `streaming_config` message and must
// not contain `audio` data. All subsequent messages must contain `audio` data
// and must not contain a `streaming_config` message.
message StreamingRecognizeRequest {
  oneof streaming_request {
    // The `streaming_config` message provides information to the recognizer
    // that specifies how to process the request.
    //
    // The first `StreamingRecognizeRequest` message must contain a
    // `streaming_config`  message.
    StreamingRecognitionConfig streaming_config = 1;

    // The audio data to be recognized. Sequential chunks of audio data are sent
    // in sequential `StreamingRecognizeRequest` messages. The first
    // `StreamingRecognizeRequest` message must not contain `audio_content` data
    // and all subsequent `StreamingRecognizeRequest` messages must contain
    // `audio_content` data. The audio bytes must be encoded as specified in
    // `RecognitionConfig`. Note: as with all bytes fields, protobuffers use a
    // pure binary representation (not base64).
    bytes audio_content = 2;
  }
}

// The `StreamingRecognitionConfig` message provides information to the
// recognizer that specifies how to process the request.
message StreamingRecognitionConfig {
  // [Required] The `config` message provides information to the recognizer
  // that specifies how to process the request.
  RecognitionConfig config = 1;

  // [Optional] If `false` or omitted, the recognizer will perform continuous
  // recognition (continuing to process audio even if the user pauses speaking)
  // until the client closes the output stream (gRPC API) or when the maximum
  // time limit has been reached. Multiple `SpeechRecognitionResult`s with the
  // `is_final` flag set to `true` may be returned.
  //
  // If `true`, the recognizer will detect a single spoken utterance. When it
  // detects that the user has paused or stopped speaking, it will return an
  // `END_OF_UTTERANCE` event and cease recognition. It will return no more than
  // one `SpeechRecognitionResult` with the `is_final` flag set to `true`.
  bool single_utterance = 2;

  // [Optional] If `true`, interim results (tentative hypotheses) may be
  // returned as they become available (these interim results are indicated with
  // the `is_final=false` flag).
  // If `false` or omitted, only `is_final=true` result(s) are returned.
  bool interim_results = 3;
}

// The `RecognitionConfig` message provides information to the recognizer
// that specifies how to process the request.
message RecognitionConfig {
  // Audio encoding of the data sent in the audio message. All encodings support
  // only 1 channel (mono) audio. Only `FLAC` includes a header that describes
  // the bytes of audio that follow the header. The other encodings are raw
  // audio bytes with no header.
  //
  // For best results, the audio source should be captured and transmitted using
  // a lossless encoding (`FLAC` or `LINEAR16`). Recognition accuracy may be
  // reduced if lossy codecs (such as AMR, AMR_WB and MULAW) are used to capture
  // or transmit the audio, particularly if background noise is present.
  enum AudioEncoding {
    // Not specified. Will return result [google.rpc.Code.INVALID_ARGUMENT][google.rpc.Code.INVALID_ARGUMENT].
    ENCODING_UNSPECIFIED = 0;

    // Uncompressed 16-bit signed little-endian samples.
    // This is the only encoding that may be used by `AsyncRecognize`.
    LINEAR16 = 1;

    // This is the recommended encoding for `SyncRecognize` and
    // `StreamingRecognize` because it uses lossless compression; therefore
    // recognition accuracy is not compromised by a lossy codec.
    //
    // The stream FLAC (Free Lossless Audio Codec) encoding is specified at:
    // http://flac.sourceforge.net/documentation.html.
    // Only 16-bit samples are supported.
    // Not all fields in STREAMINFO are supported.
    FLAC = 2;

    // 8-bit samples that compand 14-bit audio samples using G.711 PCMU/mu-law.
    MULAW = 3;

    // Adaptive Multi-Rate Narrowband codec. `sample_rate` must be 8000 Hz.
    AMR = 4;

    // Adaptive Multi-Rate Wideband codec. `sample_rate` must be 16000 Hz.
    AMR_WB = 5;
  }

  // [Required] Encoding of audio data sent in all `RecognitionAudio` messages.
  AudioEncoding encoding = 1;

  // [Required] Sample rate in Hertz of the audio data sent in all
  // `RecognitionAudio` messages. Valid values are: 8000-48000.
  // 16000 is optimal. For best results, set the sampling rate of the audio
  // source to 16000 Hz. If that's not possible, use the native sample rate of
  // the audio source (instead of re-sampling).
  int32 sample_rate = 2;

  // [Optional] The language of the supplied audio as a BCP-47 language tag.
  // Example: "en-GB"  https://www.rfc-editor.org/rfc/bcp/bcp47.txt
  // If omitted, defaults to "en-US". See
  // [Language Support](/speech/docs/best-practices#language_support) for
  // a list of the currently supported language codes.
  string language_code = 3;

  // [Optional] Maximum number of recognition hypotheses to be returned.
  // Specifically, the maximum number of `SpeechRecognitionAlternative` messages
  // within each `SpeechRecognitionResult`.
  // The server may return fewer than `max_alternatives`.
  // Valid values are `0`-`30`. A value of `0` or `1` will return a maximum of
  // `1`. If omitted, defaults to `1`.
  int32 max_alternatives = 4;

  // [Optional] If set to `true`, the server will attempt to filter out
  // profanities, replacing all but the initial character in each filtered word
  // with asterisks, e.g. "f***". If set to `false` or omitted, profanities
  // won't be filtered out.
  bool profanity_filter = 5;

  // [Optional] A means to provide context to assist the speech recognition.
  SpeechContext speech_context = 6;
}

// Provides "hints" to the speech recognizer to favor specific words and phrases
// in the results.
message SpeechContext {
  // [Optional] A list of up to 50 phrases of up to 100 characters each to
  // provide words and phrases "hints" to the speech recognition so that it is
  // more likely to recognize them.
  repeated string phrases = 1;
}

// Contains audio data in the encoding specified in the `RecognitionConfig`.
// Either `content` or `uri` must be supplied. Supplying both or neither
// returns [google.rpc.Code.INVALID_ARGUMENT][google.rpc.Code.INVALID_ARGUMENT].
message RecognitionAudio {
  oneof audio_source {
    // The audio data bytes encoded as specified in
    // `RecognitionConfig`. Note: as with all bytes fields, protobuffers use a
    // pure binary representation, whereas JSON representations use base64.
    bytes content = 1;

    // URI that points to a file that contains audio data bytes as specified in
    // `RecognitionConfig`. Currently, only Google Cloud Storage URIs are
    // supported, which must be specified in the following format:
    // `gs://bucket_name/object_name` (other URI formats return
    // [google.rpc.Code.INVALID_ARGUMENT][google.rpc.Code.INVALID_ARGUMENT]). For more information, see
    // [Request URIs](/storage/docs/reference-uris).
    string uri = 2;
  }
}

// `SyncRecognizeResponse` is the only message returned to the client by
// `SyncRecognize`. It contains the result as zero or more
// sequential `RecognizeResponse` messages.
message SyncRecognizeResponse {
  // [Output-only] Sequential list of transcription results corresponding to
  // sequential portions of audio.
  repeated SpeechRecognitionResult results = 2;
}

// `AsyncRecognizeResponse` is the only message returned to the client by
// `AsyncRecognize`. It contains the result as zero or more
// sequential `RecognizeResponse` messages.
message AsyncRecognizeResponse {
  // [Output-only] Sequential list of transcription results corresponding to
  // sequential portions of audio.
  repeated SpeechRecognitionResult results = 2;
}

// `StreamingRecognizeResponse` is the only message returned to the client by
// `StreamingRecognize`. It contains the result as zero or more
// sequential `RecognizeResponse` messages.
message StreamingRecognizeResponse {
  // Indicates the type of endpointer event.
  enum EndpointerType {
    // No endpointer event specified.
    ENDPOINTER_EVENT_UNSPECIFIED = 0;

    // Speech has been detected in the audio stream.
    START_OF_SPEECH = 1;

    // Speech has ceased to be detected in the audio stream.
    END_OF_SPEECH = 2;

    // The end of the audio stream has been reached. and it is being processed.
    END_OF_AUDIO = 3;

    // This event is only sent when `single_utterance` is `true`. It indicates
    // that the server has detected the end of the user's speech utterance and
    // expects no additional speech. Therefore, the server will not process
    // additional audio. The client should stop sending additional audio data.
    END_OF_UTTERANCE = 4;
  }

  // [Output-only] If set, returns a [google.rpc.Status][] message that
  // specifies the error for the operation.
  google.rpc.Status error = 1;

  // [Output-only] This repeated list contains zero or more results that
  // correspond to consecutive portions of the audio currently being processed.
  // It contains zero or one `is_final=true` result (the newly settled portion),
  // followed by zero or more `is_final=false` results.
  repeated StreamingRecognitionResult results = 2;

  // [Output-only] Indicates the lowest index in the `results` array that has
  // changed. The repeated `SpeechRecognitionResult` results overwrite past
  // results at this index and higher.
  int32 result_index = 3;

  // [Output-only] Indicates the type of endpointer event.
  EndpointerType endpointer_type = 4;
}

// A speech recognition result corresponding to a portion of the audio that is
// currently being processed.
message StreamingRecognitionResult {
  // [Output-only] May contain one or more recognition hypotheses (up to the
  // maximum specified in `max_alternatives`).
  repeated SpeechRecognitionAlternative alternatives = 1;

  // [Output-only] If `false`, this `SpeechRecognitionResult` represents an
  // interim result that may change. If `true`, this is the final time the
  // speech service will return this particular `SpeechRecognitionResult`,
  // the recognizer will not return any further hypotheses for this portion of
  // the transcript and corresponding audio.
  bool is_final = 2;

  // [Output-only] An estimate of the probability that the recognizer will not
  // change its guess about this interim result. Values range from 0.0
  // (completely unstable) to 1.0 (completely stable). Note that this is not the
  // same as `confidence`, which estimates the probability that a recognition
  // result is correct.
  // This field is only provided for interim results (`is_final=false`).
  // The default of 0.0 is a sentinel value indicating stability was not set.
  float stability = 3;
}

// A speech recognition result corresponding to a portion of the audio.
message SpeechRecognitionResult {
  // [Output-only] May contain one or more recognition hypotheses (up to the
  // maximum specified in `max_alternatives`).
  repeated SpeechRecognitionAlternative alternatives = 1;
}

// Alternative hypotheses (a.k.a. n-best list).
message SpeechRecognitionAlternative {
  // [Output-only] Transcript text representing the words that the user spoke.
  string transcript = 1;

  // [Output-only] The confidence estimate between 0.0 and 1.0. A higher number
  // means the system is more confident that the recognition is correct.
  // This field is typically provided only for the top hypothesis, and only for
  // `is_final=true` results.
  // The default of 0.0 is a sentinel value indicating confidence was not set.
  float confidence = 2;
}