repeat-tbc

#!/usr/bin/python3
# Given a PAL .tbc file, repeat it N times. Trim the end of the part being
# repeating to a multiple of 8 fields to keep the PAL sequence intact.
#
# Usage: repeat-tbc input.tbc output.tbc N

import optparse
import os
import sys

# Parse command-line options
parser = optparse.OptionParser(usage="usage: %prog [options] TBC-IN-FILE TBC-OUT-FILE REPS")
options, args = parser.parse_args(sys.argv[1:])

if len(args) != 3:
    parser.error("wrong number of args")

input_tbc = args[0]
output_tbc = args[1]
reps = int(args[2])

with open(input_tbc, "rb") as fin:
    # Measure the length of the video
    input_len = os.fstat(fin.fileno()).st_size
    field_size = 2 * 313 * 1135
    num_fields = input_len // field_size
    if (input_len % field_size) != 0:
        print("TBC length", input_len, "is not a multiple of field size",
              field_size, file=sys.stderr)
        sys.exit(1)

    # Trim to keep the PAL sequence intact
    dup_fields = (num_fields // 8) * 8
    print("Repeating", dup_fields, "fields of", num_fields, "to give", dup_fields * reps)

    with open(output_tbc, "wb") as fout:
        for i in range(reps):
            fin.seek(0)
            for j in range(dup_fields):
                data = fin.read(field_size)
                fout.write(data)