#!/usr/bin/env python3 from logging import getLogger from typing import Iterator, List, Optional, Union import numpy as np import torch from whisper import Whisper, load_model from whisper.audio import ( HOP_LENGTH, N_FRAMES, SAMPLE_RATE, log_mel_spectrogram, pad_or_trim, ) from whisper.decoding import DecodingOptions, DecodingResult from whisper.tokenizer import get_tokenizer from whisper.utils import exact_div from whisper_streaming.schema import ParsedChunk, WhisperConfig logger = getLogger(__name__) class WhisperStreamingTranscriber: def _set_dtype(self, fp16: bool): self.fp16 = fp16 self.dtype = torch.float16 if fp16 else torch.float32 if self.model.device == torch.device("cpu"): if torch.cuda.is_available(): logger.warning("Performing inference on CPU when CUDA is available") if self.dtype == torch.float16: logger.warning("FP16 is not supported on CPU; using FP32 instead") self.dtype = torch.float32 if self.dtype == torch.float32: self.fp16 = False def __init__(self, *, config: WhisperConfig): self.config: WhisperConfig = config self.model: Whisper = load_model(config.model_name, device=config.device) self.tokenizer = get_tokenizer( self.model.is_multilingual, language=config.language, task="transcribe", ) self._set_dtype(config.fp16) self.timestamp: float = 0.0 self.input_stride = exact_div( N_FRAMES, self.model.dims.n_audio_ctx ) # mel frames per output token: 2 self.time_precision = ( self.input_stride * HOP_LENGTH / SAMPLE_RATE ) # time per output token: 0.02 (seconds) self.buffer_tokens = [] self.buffer_mel = None def _get_decoding_options( self, *, t, prompt, beam_size: Optional[int], patience: float, best_of: Optional[int], ) -> DecodingOptions: return DecodingOptions( task="transcribe", language=None, temperature=t, sample_len=None, best_of=best_of, beam_size=beam_size, patience=patience, length_penalty=None, prompt=prompt, prefix=None, suppress_blank=True, suppress_tokens="-1", without_timestamps=False, max_initial_timestamp=0.0, fp16=self.fp16, ) def _decode_with_fallback( self, *, segment: np.ndarray, ) -> List[DecodingResult]: assert len(self.config.temperatures) >= 1 t = self.config.temperatures[0] _decode_options1: DecodingOptions = self._get_decoding_options( t=t, prompt=self.buffer_tokens, beam_size=self.config.beam_size, patience=0.0, best_of=None, ) results: List[DecodingResult] = self.model.decode(segment, _decode_options1) # type: ignore for t in self.config.temperatures[1:]: needs_fallback = [ self.config.compression_ratio_threshold is not None and result.compression_ratio > self.config.compression_ratio_threshold or self.config.logprob_threshold is not None and result.avg_logprob < self.config.logprob_threshold for result in results ] if any(needs_fallback): _decode_options2: DecodingOptions = self._get_decoding_options( t=t, prompt=self.buffer_tokens, beam_size=None, patience=0.0, best_of=self.config.best_of, ) retries: List[DecodingResult] = self.model.decode( segment[needs_fallback], _decode_options2 # type: ignore ) for retry_index, original_index in enumerate( np.nonzero(needs_fallback)[0] ): results[original_index] = retries[retry_index] return results def _get_chunk( self, *, start: float, end: float, text_tokens: torch.Tensor, result: DecodingResult, ) -> Optional[ParsedChunk]: text = self.tokenizer.decode( [token for token in text_tokens if token < self.tokenizer.eot] # type: ignore ) if len(text.strip()) == 0: # skip empty text output return return ParsedChunk( start=start, end=end, text=text, tokens=result.tokens, temperature=result.temperature, avg_logprob=result.avg_logprob, compression_ratio=result.compression_ratio, no_speech_prob=result.no_speech_prob, ) def _deal_timestamp( self, *, result, segment_duration ) -> Iterator[Union[ParsedChunk, int]]: tokens = torch.tensor(result.tokens) timestamp_tokens: torch.Tensor = tokens.ge(self.tokenizer.timestamp_begin) consecutive = torch.where(timestamp_tokens[:-1] & timestamp_tokens[1:])[0].add_( 1 ) if ( len(consecutive) > 0 ): # if the output contains two consecutive timestamp tokens logger.debug(f"Length of consecutive: {len(consecutive)}") last_slice = 0 for current_slice in consecutive: logger.debug(f" last_slice={last_slice}, current_slice={current_slice}") sliced_tokens = tokens[last_slice:current_slice] start_timestamp_position = ( sliced_tokens[0].item() - self.tokenizer.timestamp_begin ) end_timestamp_position = ( sliced_tokens[-1].item() - self.tokenizer.timestamp_begin ) chunk = self._get_chunk( start=self.timestamp + start_timestamp_position * self.time_precision, end=self.timestamp + end_timestamp_position * self.time_precision, text_tokens=sliced_tokens[1:-1], result=result, ) if chunk is not None: yield chunk last_slice = current_slice last_timestamp_position0: int = ( tokens[last_slice - 1].item() - self.tokenizer.timestamp_begin # type:ignore ) self.buffer_tokens.extend(tokens[: last_slice + 1].tolist()) self.timestamp += last_timestamp_position0 * self.time_precision yield last_timestamp_position0 else: logger.debug("Length of consecutive: 0") duration = segment_duration timestamps = tokens[timestamp_tokens.nonzero().flatten()] if len(timestamps) > 0: # no consecutive timestamps but it has a timestamp; use the last one. # single timestamp at the end means no speech after the last timestamp. last_timestamp_position = ( timestamps[-1].item() - self.tokenizer.timestamp_begin ) duration = last_timestamp_position * self.time_precision chunk = self._get_chunk( start=self.timestamp, end=self.timestamp + duration, text_tokens=tokens, result=result, ) if chunk is not None: yield chunk self.timestamp += duration if result.temperature > 0.5: # do not feed the prompt tokens if a high temperature was used del self.buffer_tokens self.buffer_tokens = [] logger.debug(f"Length of buffer: {len(self.buffer_tokens)}") def transcribe( self, *, segment: np.ndarray, ) -> Iterator[ParsedChunk]: new_mel = log_mel_spectrogram(audio=segment).unsqueeze(0) if self.buffer_mel is None: mel = new_mel else: mel = torch.cat([self.buffer_mel, new_mel], dim=-1) self.buffer_mel = None seek: int = 0 rest_start: Optional[int] = None while seek < mel.shape[-1]: logger.debug( f"seek={seek}, timestamp={self.timestamp}, rest_start={rest_start}" ) segment = ( pad_or_trim(mel[:, :, seek:], N_FRAMES) .to(self.model.device) # type: ignore .to(self.dtype) ) results = self._decode_with_fallback( segment=segment, ) result = results[0] logger.debug( f"Result: temperature={result.temperature}, no_speech_prob={result.no_speech_prob}, " f"avg_logprob={result.avg_logprob}" ) if self.config.no_speech_threshold is not None: if (result.no_speech_prob > self.config.no_speech_threshold) and not ( self.config.logprob_threshold is not None and result.avg_logprob > self.config.logprob_threshold ): seek += segment.shape[-1] rest_start = None continue segment_duration = segment.shape[-1] * HOP_LENGTH / SAMPLE_RATE last_timestamp_position: Optional[int] = None for v in self._deal_timestamp( result=result, segment_duration=segment_duration ): if isinstance(v, int): last_timestamp_position = v else: yield v if last_timestamp_position is None: seek += segment.shape[-1] rest_start = None else: seek += last_timestamp_position rest_start = seek logger.debug(f"Last rest_start={rest_start}") if rest_start is None: return self.buffer_mel = mel[:, :, rest_start:] del mel