*This model was published in HF papers on 2021-04-14 and contributed to Hugging Face Transformers on 2021-09-01.* # Speech Encoder Decoder Models

The [`SpeechEncoderDecoderModel`] can be used to initialize a speech-to-text model with any pretrained speech autoencoding model as the encoder (*e.g.* [Wav2Vec2](wav2vec2), [Hubert](hubert)) and any pretrained autoregressive model as the decoder. The effectiveness of initializing speech-sequence-to-text-sequence models with pretrained checkpoints for speech recognition and speech translation has *e.g.* been shown in [Large-Scale Self- and Semi-Supervised Learning for Speech Translation](https://huggingface.co/papers/2104.06678) by Changhan Wang, Anne Wu, Juan Pino, Alexei Baevski, Michael Auli, Alexis Conneau. An example of how to use a [`SpeechEncoderDecoderModel`] for inference can be seen in [Speech2Text2](speech_to_text_2). ## Randomly initializing `SpeechEncoderDecoderModel` from model configurations [`SpeechEncoderDecoderModel`] can be randomly initialized from an encoder and a decoder config. In the following example, we show how to do this using the default [`Wav2Vec2Model`] configuration for the encoder and the default [`BertForCausalLM`] configuration for the decoder. ```python from transformers import BertConfig, SpeechEncoderDecoderConfig, SpeechEncoderDecoderModel, Wav2Vec2Config config_encoder = Wav2Vec2Config() config_decoder = BertConfig() config = SpeechEncoderDecoderConfig.from_encoder_decoder_configs(config_encoder, config_decoder) model = SpeechEncoderDecoderModel(config=config) ``` ## Initialising `SpeechEncoderDecoderModel` from a pretrained encoder and a pretrained decoder [`SpeechEncoderDecoderModel`] can be initialized from a pretrained encoder checkpoint and a pretrained decoder checkpoint. Note that any pretrained Transformer-based speech model, *e.g.* [Wav2Vec2](wav2vec2), [Hubert](hubert) can serve as the encoder and both pretrained auto-encoding models, *e.g.* BERT, pretrained causal language models, *e.g.* GPT2, as well as the pretrained decoder part of sequence-to-sequence models, *e.g.* decoder of BART, can be used as the decoder. Depending on which architecture you choose as the decoder, the cross-attention layers might be randomly initialized. Initializing [`SpeechEncoderDecoderModel`] from a pretrained encoder and decoder checkpoint requires the model to be fine-tuned on a downstream task, as has been shown in [the *Warm-starting-encoder-decoder blog post*](https://huggingface.co/blog/warm-starting-encoder-decoder). To do so, the `SpeechEncoderDecoderModel` class provides a [`SpeechEncoderDecoderModel.from_encoder_decoder_pretrained`] method. ```python from transformers import SpeechEncoderDecoderModel model = SpeechEncoderDecoderModel.from_encoder_decoder_pretrained( "facebook/hubert-large-ll60k", "google-bert/bert-base-uncased" ) ``` ## Loading an existing `SpeechEncoderDecoderModel` checkpoint and perform inference To load fine-tuned checkpoints of the `SpeechEncoderDecoderModel` class, [`SpeechEncoderDecoderModel`] provides the `from_pretrained(...)` method just like any other model architecture in Transformers. To perform inference, one uses the [`generate`] method, which allows to autoregressively generate text. This method supports various forms of decoding, such as greedy, beam search and multinomial sampling. ```python from transformers import Wav2Vec2Processor, SpeechEncoderDecoderModel from datasets import load_dataset import torch # load a fine-tuned speech translation model and corresponding processor model = SpeechEncoderDecoderModel.from_pretrained("facebook/wav2vec2-xls-r-300m-en-to-15", device_map="auto") processor = Wav2Vec2Processor.from_pretrained("facebook/wav2vec2-xls-r-300m-en-to-15") # let's perform inference on a piece of English speech (which we'll translate to German) ds = load_dataset("hf-internal-testing/librispeech_asr_dummy", "clean", split="validation") input_values = processor(ds[0]["audio"]["array"], return_tensors="pt").to(model.device).input_values # autoregressively generate transcription (uses greedy decoding by default) generated_ids = model.generate(input_values) generated_text = processor.batch_decode(generated_ids, skip_special_tokens=True)[0] print(generated_text) Mr. Quilter ist der Apostel der Mittelschicht und wir freuen uns, sein Evangelium willkommen heißen zu können. ``` ## Training Once the model is created, it can be fine-tuned similar to BART, T5 or any other encoder-decoder model on a dataset of (speech, text) pairs. As you can see, only 2 inputs are required for the model in order to compute a loss: `input_values` (which are the speech inputs) and `labels` (which are the `input_ids` of the encoded target sequence). ```python from datasets import load_dataset from transformers import AutoFeatureExtractor, AutoTokenizer, SpeechEncoderDecoderModel encoder_id = "facebook/wav2vec2-base-960h" # acoustic model encoder decoder_id = "google-bert/bert-base-uncased" # text decoder feature_extractor = AutoFeatureExtractor.from_pretrained(encoder_id) tokenizer = AutoTokenizer.from_pretrained(decoder_id) # Combine pre-trained encoder and pre-trained decoder to form a Seq2Seq model model = SpeechEncoderDecoderModel.from_encoder_decoder_pretrained(encoder_id, decoder_id) model.config.decoder_start_token_id = tokenizer.cls_token_id model.config.pad_token_id = tokenizer.pad_token_id # load an audio input and pre-process (normalise mean/std to 0/1) ds = load_dataset("hf-internal-testing/librispeech_asr_dummy", "clean", split="validation") input_values = feature_extractor(ds[0]["audio"]["array"], return_tensors="pt").to(model.device).input_values # load its corresponding transcription and tokenize to generate labels labels = tokenizer(ds[0]["text"], return_tensors="pt").to(model.device).input_ids # the forward function automatically creates the correct decoder_input_ids loss = model(input_values=input_values, labels=labels).loss loss.backward() ``` ## SpeechEncoderDecoderConfig [[autodoc]] SpeechEncoderDecoderConfig ## SpeechEncoderDecoderModel [[autodoc]] SpeechEncoderDecoderModel - forward - from_encoder_decoder_pretrained