Control stream (07/11/98)
-------------------------

entry ::= identifier length data_0 data_1 data_2 data_3 data_4

identifier ::= P | G | M
length     ::= 16 bit unsigned integer
data_x     ::= 16 bit signed integer

if (identifier == 'P')
   -1   // data_0
   -1   // ...
   -1   //
   -1   //
   -1   // data_4
endif

if (identifier == 'G')
   Group number
   GQUANT       // quantizer
   -1
   -1
   -1
endif

if (identifier == 'M')
   MBA          // macroblock address (relativ)
   MTYPE == MC  // macroblock with motion compensation?
   QUANT | -1   // quantizer
   HMV   | -1   // reference motion vector (horizontal component)
   VMV   | -1   // reference motion vector (vertical component)
endif