Added audio duration after VAD to TranscriptionInfo object (#445)

* Added VAD removed audio duration to TranscriptionInfo object

Along with the duration of the original audio, this commit  adds the seconds of audio removed by the VAD to the returned info obj

* Chaning naming for duration_after_vad

Instead of the property returning the audio duration removed, it now returns the final duration after the vad.
If vad_filter is False or if it doesn't remove any audio, the original duration is returned.

faster_whisper/transcribe.py

@@ -69,6 +69,7 @@ class TranscriptionInfo(NamedTuple):
     language: str
     language_probability: float
     duration: float
+    duration_after_vad: float
     all_language_probs: Optional[List[Tuple[str, float]]]
     transcription_options: TranscriptionOptions
     vad_options: VadOptions
@@ -249,6 +250,7 @@ class WhisperModel:
             audio = decode_audio(audio, sampling_rate=sampling_rate)
 
         duration = audio.shape[0] / sampling_rate
+        duration_after_vad = duration
 
         self.logger.info(
             "Processing audio with duration %s", format_timestamp(duration)
@@ -261,10 +263,11 @@ class WhisperModel:
                 vad_parameters = VadOptions(**vad_parameters)
             speech_chunks = get_speech_timestamps(audio, vad_parameters)
             audio = collect_chunks(audio, speech_chunks)
+            duration_after_vad = audio.shape[0] / sampling_rate
 
             self.logger.info(
                 "VAD filter removed %s of audio",
-                format_timestamp(duration - (audio.shape[0] / sampling_rate)),
+                format_timestamp(duration - duration_after_vad),
             )
 
             if self.logger.isEnabledFor(logging.DEBUG):
@@ -352,6 +355,7 @@ class WhisperModel:
             language=language,
             language_probability=language_probability,
             duration=duration,
+            duration_after_vad=duration_after_vad,
             transcription_options=options,
             vad_options=vad_parameters,
             all_language_probs=all_language_probs,