Bidrectionally Coded Pictures

Pictures with bidirectional prediction refer not only to the preceding pictures, they have also the ability to access succeeding pictures. Two movement vectors refer to both an older segment and a segment later following. Only the interpolation between them is encoded. All subsequent steps are identical to the equivalent P-picture coding.

A B-picture must always refer on a P- or a I-picture, references to B-pictures are not permitted. Irregular recursions could arise if two B-pictures point at each other mutually.

 <   ^   >