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# Speech2Text

## Overview

The Speech2Text model was proposed in [fairseq S2T: Fast Speech-to-Text Modeling with fairseq](https://arxiv.org/abs/2010.05171) by Changhan Wang, Yun Tang, Xutai Ma, Anne Wu, Dmytro Okhonko, Juan Pino. It's a
transformer-based seq2seq (encoder-decoder) model designed for end-to-end Automatic Speech Recognition (ASR) and Speech
Translation (ST). It uses a convolutional downsampler to reduce the length of speech inputs by 3/4th before they are
fed into the encoder. The model is trained with standard autoregressive cross-entropy loss and generates the
transcripts/translations autoregressively. Speech2Text has been fine-tuned on several datasets for ASR and ST:
[LibriSpeech](http://www.openslr.org/12), [CoVoST 2](https://github.com/facebookresearch/covost), [MuST-C](https://ict.fbk.eu/must-c/).

This model was contributed by [valhalla](https://huggingface.co/valhalla). The original code can be found [here](https://github.com/pytorch/fairseq/tree/master/examples/speech_to_text).


## Inference

Speech2Text is a speech model that accepts a float tensor of log-mel filter-bank features extracted from the speech
signal. It's a transformer-based seq2seq model, so the transcripts/translations are generated autoregressively. The
`generate()` method can be used for inference.

The [`Speech2TextFeatureExtractor`] class is responsible for extracting the log-mel filter-bank
features. The [`Speech2TextProcessor`] wraps [`Speech2TextFeatureExtractor`] and
[`Speech2TextTokenizer`] into a single instance to both extract the input features and decode the
predicted token ids.

The feature extractor depends on `torchaudio` and the tokenizer depends on `sentencepiece` so be sure to
install those packages before running the examples. You could either install those as extra speech dependencies with
`pip install transformers"[speech, sentencepiece]"` or install the packages seperately with `pip install torchaudio sentencepiece`. Also `torchaudio` requires the development version of the [libsndfile](http://www.mega-nerd.com/libsndfile/) package which can be installed via a system package manager. On Ubuntu it can
be installed as follows: `apt install libsndfile1-dev`


- ASR and Speech Translation

```python
>>> import torch
>>> from transformers import Speech2TextProcessor, Speech2TextForConditionalGeneration
>>> from datasets import load_dataset
>>> import soundfile as sf

>>> model = Speech2TextForConditionalGeneration.from_pretrained("facebook/s2t-small-librispeech-asr")
>>> processor = Speech2TextProcessor.from_pretrained("facebook/s2t-small-librispeech-asr")

>>> def map_to_array(batch):
...     speech, _ = sf.read(batch["file"])
...     batch["speech"] = speech
...     return batch

>>> ds = load_dataset("hf-internal-testing/librispeech_asr_dummy", "clean", split="validation")
>>> ds = ds.map(map_to_array)

>>> inputs = processor(ds["speech"][0], sampling_rate=16_000, return_tensors="pt")
>>> generated_ids = model.generate(input_ids=inputs["input_features"], attention_mask=inputs["attention_mask"])

>>> transcription = processor.batch_decode(generated_ids)
```

- Multilingual speech translation

  For multilingual speech translation models, `eos_token_id` is used as the `decoder_start_token_id` and
  the target language id is forced as the first generated token. To force the target language id as the first
  generated token, pass the `forced_bos_token_id` parameter to the `generate()` method. The following
  example shows how to transate English speech to French text using the *facebook/s2t-medium-mustc-multilingual-st*
  checkpoint.

```python
>>> import torch
>>> from transformers import Speech2TextProcessor, Speech2TextForConditionalGeneration
>>> from datasets import load_dataset
>>> import soundfile as sf

>>> model = Speech2TextForConditionalGeneration.from_pretrained("facebook/s2t-medium-mustc-multilingual-st")
>>> processor = Speech2TextProcessor.from_pretrained("facebook/s2t-medium-mustc-multilingual-st")

>>> def map_to_array(batch):
...     speech, _ = sf.read(batch["file"])
...     batch["speech"] = speech
...     return batch

>>> ds = load_dataset("hf-internal-testing/librispeech_asr_dummy", "clean", split="validation")
>>> ds = ds.map(map_to_array)

>>> inputs = processor(ds["speech"][0], sampling_rate=16_000, return_tensors="pt")
>>> generated_ids = model.generate(input_ids=inputs["input_features"], attention_mask=inputs["attention_mask], forced_bos_token_id=processor.tokenizer.lang_code_to_id["fr"])

>>> translation = processor.batch_decode(generated_ids)
```

See the [model hub](https://huggingface.co/models?filter=speech_to_text) to look for Speech2Text checkpoints.


## Speech2TextConfig

[[autodoc]] Speech2TextConfig

## Speech2TextTokenizer

[[autodoc]] Speech2TextTokenizer
    - build_inputs_with_special_tokens
    - get_special_tokens_mask
    - create_token_type_ids_from_sequences
    - save_vocabulary

## Speech2TextFeatureExtractor

[[autodoc]] Speech2TextFeatureExtractor
    - __call__

## Speech2TextProcessor

[[autodoc]] Speech2TextProcessor
    - __call__
    - from_pretrained
    - save_pretrained
    - batch_decode
    - decode
    - as_target_processor

## Speech2TextModel

[[autodoc]] Speech2TextModel
    - forward

## Speech2TextForConditionalGeneration

[[autodoc]] Speech2TextForConditionalGeneration
    - forward
