mxf.py

import sys import struct # MXF Keys MXF_KEYS = { '\x06\x0e\x2b\x34\x02\x53\x01\x01\x0d\x01\x01\x01\x01\x01\x51\x00' : 'MPEG2VIDEODESCRIPTOR', '\x06\x0e\x2b\x34\x02\x53\x01\x01\x0d\x01\x01\x01\x01\x01\x5a\x00' : 'JPEG2000PICTURESUBDESCRIPTOR', '\x06\x0e\x2b\x34\x02\x53\x01\x01\x0d\x01\x01\x01\x01\x01\x48\x00' : 'WAVEAUDIODESCRIPTOR', '\x06\x0e\x2b\x34\x02\x53\x01\x01\x0d\x01\x01\x01\x01\x01\x37\x00' : 'SOURCEPACKAGE', '\x06\x0e\x2b\x34\x01\x02\x01\x01\x0d\x01\x03\x01\x15\x01\x05\x00' : 'MPEG2ESSENCE', '\x06\x0e\x2b\x34\x01\x02\x01\x01\x0d\x01\x03\x01\x15\x01\x08\x00' : 'JPEG2000ESSENCE', '\x06\x0e\x2b\x34\x01\x02\x01\x01\x0d\x01\x03\x01\x16\x01\x01\x00' : 'WAVESSENCE' } def _as_hex_str(bytes): """ Pretty-prints bytes as hex values separated by dots """ return '.'.join(map(lambda x: '%02X' % ord(x), bytes)) def _decode_ber_length(reader): """ Dynamically works out a BER-encoded length value from a stream.read function. Returns the decoded length and nr of bytes read """ length = struct.unpack('>B', reader(1))[0] # Get the first byte and decode it bytes_read = 1 if length > 127: bytes_read += length - 128 length = int(reader(length - 128).encode('hex'), 16) # Read the bytes and convert return (length, bytes_read) def klvs(stream): """ Generator that iterates through KLVs that are dynamically read from a stream """ klv_key_length = 16 pos = 0 while True: key = stream.read(klv_key_length) if not key: break (length, len_bytes) = _decode_ber_length(stream.read) value = stream.read(length) pos += 4 + len_bytes + length yield (MXF_KEYS.get(key, _as_hex_str(key)), value) def print_klv_keys(mxf_filename): """ Prints out all klv keys found in an mxf file """ with open(mxf_filename, 'rb') as mxf_file: for klv in klvs(mxf_file): print klv[0] def essence_type(mxf_filename): """ Returns 'JPEG2000', 'MPEG2' or 'PCM' depending on the essence type contained within the mxf file """ with open(mxf_filename, 'rb') as mxf_file: for klv in klvs(mxf_file): if klv[0] == 'JPEG2000PICTURESUBDESCRIPTOR': return 'JPEG2000' elif klv[0] == 'MPEG2VIDEODESCRIPTOR': return 'MPEG2' elif klv[0] == 'WAVEAUDIODESCRIPTOR': return 'PCM' if __name__ == '__main__': if len(sys.argv) != 2: print 'USAGE: python mxf.py <mxf file name>' else: # print_klv_keys(sys.argv[1]) print essence_type(sys.argv[1])