Extracts lens Focal Length metadata from Canon C300 MXF files. Put the search dir in "rootdir" variable, where the MXF files are located (can be in subdirs also). Outputs "output.txt" with ShotName / FocalLength range tabulated values on each line.

mxf.py

import sys
import struct
import os

rootdir = "D:/MXF_Day1_Shots"

# MXF Keys
MXF_KEYS = {
    '\x06\x0E\x2B\x34\x02\x43\x01\x01\x0D\x01\x03\x01\x04\x01\x02\x02' : 'FRAME'
}


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 toFocalLength(data):
  return str(data)[:-1] + "." + str(data)[-1:] 

def essence_type(mxf_filename):
    with open(mxf_filename, 'rb') as mxf_file:
        mindata = 100000
        maxdata = 0
        for klv in klvs(mxf_file):
           if klv[0] == "FRAME":
             data = int(klv[1][97:99].encode('hex'), 16)
             if data < mindata:
               mindata = data
             if data > maxdata:
               maxdata = data
  if mindata == maxdata:
          f1.write(file + "\t" + toFocalLength(mindata) + " mm\n")
        else:
          f1.write(file + "\t" + toFocalLength(mindata) + " - " + toFocalLength(maxdata) + " mm\n")
            

f1 = open('output.txt', 'w')
for root, subFolders, files in os.walk(rootdir):
    for file in files:
        if file.endswith(".MXF"):
            print file
       	    essence_type(os.path.join(root, file))
f1.close()