DCT Coefficient in MPEG2 Bitstream ISO/IEC standards

[shaklasah]

Hi,

I am having difficulty parsing MPEG2 video bitstream. I have an encoded MPEG2 video in a binary file and I want to use one of the "Selective Encryption Algorithms" that encrypts only the "DC signs in intra-macroblocks".

Anyone can help me fining DC Coefficients and AC Coefficient in a bitsream. I mean is there a specific header for that like the one the sequence start by of the picture,... etc


Thanks a lot