MPEG 2 Transport Stream + MP2 Video DAR Aspect Detector

mp2aspect.py

# An Display aspect ratio (DAR) detector for MPEG 2 Transport Streams with MP2 Video
 
import array
import logging
import sys
 
class NullHandler(logging.Handler):
    def emit(self, record):
        pass
       
h = NullHandler()
logger = logging.getLogger("mpeg2video")
logger.addHandler(h)
 
aspect_ratio_dict = [ False, "1:1", "4:3", "16:9", "2.21:1" ]
 
class mpeg2video(object):
    file = None
   
    def __init__(self, file_name):
        self.file = open(file_name, "rb")
       
    def get_aspect_ratio(self):
       
        block_size = 1048576
       
        file_header = array.array('B')
        try:
            file_header.fromfile(self.file, block_size)
        except EOFError:
            logger.debug("Could not read full block_size")
            pass
       
        for i in xrange(0,len(file_header)):
           
            if (file_header[i] == 0 and
                file_header[i+1] == 0 and
                file_header[i+2] == 0x01 and
                file_header[i+3] == 0xB3):
           
                logger.debug("Found start code at %s", hex(i))
                start_data = i + 4
           
                aspect_frame_rate_byte = file_header[start_data+3]
                logger.debug("aspect_frame_rate_byte: %s", hex(aspect_frame_rate_byte))
               
                aspect_ratio_id = aspect_frame_rate_byte >> 4
                aspect_ratio = aspect_ratio_dict[aspect_ratio_id]
                return aspect_ratio
           
        logger.warning("No start code or aspect key found")
 
if __name__ == "__main__":
    logging.basicConfig(level=logging.DEBUG)
    m2v = mpeg2video(sys.argv[1])
    print m2v.get_aspect_ratio()