39 lines
1.3 KiB
Python
39 lines
1.3 KiB
Python
"""Utilities to help convert mp4s to fmp4s."""
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import io
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def find_box(segment: io.BytesIO, target_type: bytes, box_start: int = 0) -> int:
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"""Find location of first box (or sub_box if box_start provided) of given type."""
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if box_start == 0:
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box_end = segment.seek(0, io.SEEK_END)
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segment.seek(0)
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index = 0
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else:
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segment.seek(box_start)
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box_end = box_start + int.from_bytes(segment.read(4), byteorder="big")
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index = box_start + 8
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while 1:
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if index > box_end - 8: # End of box, not found
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break
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segment.seek(index)
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box_header = segment.read(8)
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if box_header[4:8] == target_type:
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yield index
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segment.seek(index)
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index += int.from_bytes(box_header[0:4], byteorder="big")
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def get_init(segment: io.BytesIO) -> bytes:
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"""Get init section from fragmented mp4."""
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moof_location = next(find_box(segment, b"moof"))
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segment.seek(0)
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return segment.read(moof_location)
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def get_m4s(segment: io.BytesIO, sequence: int) -> bytes:
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"""Get m4s section from fragmented mp4."""
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moof_location = next(find_box(segment, b"moof"))
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mfra_location = next(find_box(segment, b"mfra"))
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segment.seek(moof_location)
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return segment.read(mfra_location - moof_location)
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