mirror of
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104 lines
4.2 KiB
Python
104 lines
4.2 KiB
Python
import struct
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from .umid_parser import UMIDParser
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from typing import Optional
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class WavBextReader:
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def __init__(self, bext_data, encoding):
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"""
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Read Broadcast-WAV extended metadata.
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:param bext_data: The bytes-like data.
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:param encoding: The encoding to use when decoding the text fields of the
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BEXT metadata scope. According to EBU Rec 3285 this shall be ASCII.
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"""
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packstring = "<256s" + "32s" + "32s" + "10s" + "8s" + "QH" + "64s" + "hhhhh" + "180s"
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rest_starts = struct.calcsize(packstring)
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unpacked = struct.unpack(packstring, bext_data[:rest_starts])
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def sanitize_bytes(b : bytes) -> str:
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# honestly can't remember why I'm stripping nulls this way
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first_null = next((index for index, byte in enumerate(b) if byte == 0), None)
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trimmed = b if first_null is None else b[:first_null]
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decoded = trimmed.decode(encoding)
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return decoded
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#: Description. A free-text field up to 256 characters long.
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self.description : str = sanitize_bytes(unpacked[0])
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#: Originator. Usually the name of the encoding application, sometimes
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#: an artist name.
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self.originator : str = sanitize_bytes(unpacked[1])
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#: A unique identifier for the file, a serial number.
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self.originator_ref : str = sanitize_bytes(unpacked[2])
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#: Date of the recording, in the format YYYY-MM-DD.
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self.originator_date : str = sanitize_bytes(unpacked[3])
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#: Time of the recording, in the format HH:MM:SS.
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self.originator_time : str = sanitize_bytes(unpacked[4])
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#: The sample offset of the start, usually relative
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#: to midnight.
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self.time_reference : int = unpacked[5]
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#: A variable-length text field containing a list of processes and
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#: and conversions performed on the file.
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self.coding_history : str = sanitize_bytes(bext_data[rest_starts:])
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#: BEXT version.
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self.version : int = unpacked[6]
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#: SMPTE 330M UMID of this audio file, 64 bytes are allocated though the UMID
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#: may only be 32 bytes long.
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self.umid : Optional[bytes] = None
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#: EBU R128 Integrated loudness, in LUFS.
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self.loudness_value : Optional[float] = None
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#: EBU R128 Loudness range, in LUFS.
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self.loudness_range : Optional[float] = None
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#: True peak level, in dBFS TP
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self.max_true_peak : Optional[float] = None
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#: EBU R128 Maximum momentary loudness, in LUFS
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self.max_momentary_loudness : Optional[float] = None
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#: EBU R128 Maximum short-term loudness, in LUFS.
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self.max_shortterm_loudness : Optional[float] = None
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if self.version > 0:
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self.umid = unpacked[7]
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if self.version > 1:
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self.loudness_value = unpacked[8] / 100.0
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self.loudness_range = unpacked[9] / 100.0
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self.max_true_peak = unpacked[10] / 100.0
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self.max_momentary_loudness = unpacked[11] / 100.0
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self.max_shortterm_loudness = unpacked[12] / 100.0
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def to_dict(self):
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if self.umid is not None:
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umid_parsed = UMIDParser(self.umid)
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umid_str = umid_parsed.basic_umid_to_str()
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else:
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umid_str = None
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return {'description': self.description,
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'originator': self.originator,
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'originator_ref': self.originator_ref,
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'originator_date': self.originator_date,
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'originator_time': self.originator_time,
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'time_reference': self.time_reference,
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'version': self.version,
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'umid': umid_str,
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'coding_history': self.coding_history,
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'loudness_value': self.loudness_value,
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'loudness_range': self.loudness_range,
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'max_true_peak': self.max_true_peak,
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'max_momentary_loudness': self.max_momentary_loudness,
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'max_shortterm_loudness': self.max_shortterm_loudness
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}
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