68 lines
1.8 KiB
Python
68 lines
1.8 KiB
Python
"""We use the PyAV library to decode the audio: https://github.com/PyAV-Org/PyAV
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The advantage of PyAV is that it bundles the FFmpeg libraries so there is no additional
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system dependencies. FFmpeg does not need to be installed on the system.
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However, the API is quite low-level so we need to manipulate audio frames directly.
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"""
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import av
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import io
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import itertools
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import numpy as np
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def decode_audio(input_file, sampling_rate=16000):
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"""Decodes the audio.
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Args:
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input_file: Path to the input file or a file-like object.
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sampling_rate: Resample the audio to this sample rate.
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Returns:
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A float32 Numpy array.
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"""
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resampler = av.audio.resampler.AudioResampler(
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format="s16",
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layout="mono",
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rate=sampling_rate,
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)
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raw_buffer = io.BytesIO()
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dtype = None
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with av.open(input_file) as container:
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frames = container.decode(audio=0)
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frames = _group_frames(frames, 500000)
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frames = _resample_frames(frames, resampler)
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for frame in frames:
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array = frame.to_ndarray()
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dtype = array.dtype
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raw_buffer.write(array)
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audio = np.frombuffer(raw_buffer.getbuffer(), dtype=dtype)
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# Convert s16 back to f32.
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return audio.astype(np.float32) / 32768.0
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def _group_frames(frames, num_samples=None):
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fifo = av.audio.fifo.AudioFifo()
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for frame in frames:
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frame.pts = None # Ignore timestamp check.
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fifo.write(frame)
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if num_samples is not None and fifo.samples >= num_samples:
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yield fifo.read()
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if fifo.samples > 0:
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yield fifo.read()
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def _resample_frames(frames, resampler):
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# Add None to flush the resampler.
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for frame in itertools.chain(frames, [None]):
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yield from resampler.resample(frame)
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