c_marking() syntax structure shall not contain a memory_management_control_operation command equal to 3 that assigns a long-term frame index to a field (not marked as "reference base picture") of a reference frame or a complementary reference field pair when both of the following conditions are true (when processing the memory_management_control_operation command equal to 3): the other field of the reference frame or complementary reference field pair is marked as "unused for reference", there exists a reference base frame or a complementary reference base field pair (marked as "reference base picture") that is associated with the reference frame or complementary reference field pair, respectively, and in which both fields are marked as "used for reference". When decoding the second field (in decoding order) of a complementary reference field pair, the dec_ref_pic_marking() syntax structure shall not contain a memory_management_control_operation command equal to 6 that assigns a long-term frame index to this field when both of the following conditions are true: there exists a reference base field (marked as "reference base picture") that is associated with the first field of the complementary reference field pair and that is marked as "used for short-term reference" when the memory_management_control_operatione command equal to 6 is processed, - the dec_ref_pic_marking() syntax structure does not contain a memory_management_control_operation command equal to 3 that assigns the same long-term frame index to the first field of the complementary reference field pair. NOTE - The additional constraints specified above (in connection with the constraints specified in clause 7.4.3.3) ensure that after processing all memory_management_control_operation commands of the decoded reference picture marking syntax structure the following applies, with reference entry being a collective term for a non-paired reference field, a reference frame, or a complementary reference field pair (not marked as "reference base picture") and 