ion command (equal to 3 or 6) to assign the same long-term frame index to the other field of the same frame or complementary reference field pair shall be present in the same decoded reference picture marking syntax structure. NOTE 3 - The above requirement must be fulfilled even when the field referred to by the memory_management_control_operation equal to 3 is subsequently marked as "unused for reference" (for example when memory_management_control_operation equal to 2 is present in the same slice header that causes the field to be marked as "unused for reference"). NOTE 4 - The above requirement has the following implications: When a memory_management_control_operation equal to 3 is present that assigns a long-term frame index to a field that is part of a reference frame or complementary reference field pair with both fields marked as "used for short-term reference" (when processing thememory_management_control_operationequal to 3), another memory_management_control_operation equal to 3 must also be present in the same decoded reference picture marking syntax structure that assigns the same long-term frame index to the other field of the reference frame or complementary reference field pair. When the current picture is the second field (in decoding order) of a complementary reference field pair and a operation equal to 3 is present in the decoded reference picture marking syntax structure of the current picture that assigns a long-term frame index to the first field (in decoding order) of the complementary reference field pair, a memory_management_control operation equal to 6 must be present in the same decoded reference picture marking syntax structure that assigns the same long-term frame index to the second field of the complementary reference field pair. When the first field (in decoding order) of a complementary reference field pair included a long_term_reference_flag equal to 1 or a memory_management_control_operation command equal to 6, the decoded reference picture marking syntax structure for the seco