1. A block-constrained (BC)-Trellis coded quantization (TCQ) method comprising: constraining a number of initial states of Trellis paths available for selection, in a Trellis structure having a total of N (N=2 v , here v denotes the number of binary state variables in an encoder finite state machine) states, within 2 k (0≦k≦v) of the total N states, and constraining the number of N states of a last stage within 2 v−k among the total of N states dependent on the initial states of Trellis paths; referring to the initial states of Trellis paths determined under the initial state constraint from a first stage to a stage L-log 2 N (here, L denotes the number of entire stages and N denotes the total number of the states in the Trellis structure), considering Trellis paths in which an allowed state of the last stage is selected among 2 v−k states determined by each initial state under the constraint on the state of a last stage by the constraining in remaining v stages; and obtaining an optimum Trellis path among the considered Trellis paths and transmitting the optimum Trellis path.