An encoding apparatus for encoding frames of an input signal having a speech characteristic or an audio characteristic, the encoding apparatus comprising: a mode selection unit to analyze a characteristic of a current frame of the input signal and to select a first encoding mode for encoding the current frame; a mode buffer to store a second encoding mode for encoding the previous frame with respect to the current frame of the input signal; and a speech encoding unit to encode the current frame of the input signal based on the first encoding mode for the current frame selected by the mode selection unit and the second encoding mode for the previous frame outputted from the mode buffer; an audio encoding unit to encode the current frame of the input signal based on the first encoding mode for the current frame selected by the mode selection unit and the second encoding mode for the previous frame outputted from the mode buffer; an input buffer to output the previous frame of the input signal, and wherein the first encoding mode and the second encoding mode is either a Code Excitation Linear Prediction (CELP) scheme or a Modified Discrete Cosine Transform (MDCT) scheme, wherein the speech encoding unit comprises an encoding initialization unit and a first speech encoder, wherein the encoding initialization unit to determine an initial value used for encoding by the first speech encoder, when the first encoding mode is different from the second encoding mode for the previous frame which is MDCT scheme, wherein the first speech encoder to encode the current frame according to the CELP scheme using previous information for the previous frame, when the first encoding mode is identical to the second encoding mode which is the CELP scheme, wherein the first speech encoder to encode the current frame according to the CELP scheme using the initial value outputted from the encoding initialization unit, when the first encoding mode is different from the second encoding mode which is MDCT scheme, wherein the audio encoding unit comprise a second speech encoder, a second audio encoder, a first audio encoder, wherein the first audio encoder to encode the current frame of the input signal based on MDCT scheme, when the first encoding mode is identical to the second encoding mode for the previous frame as the MDCT scheme, wherein, when the first encoding mode is different from the second encoding mode for the previous frame which is CELP scheme, the second speech encoder encodes current frame of the input signal corresponding to a first 1/2 frame of the current frame based on the CELP scheme and, subsequently, the second audio encoder encodes the entire current frame using the MDCT scheme. a mode selection unit to analyze a characteristic of a current frame of the input signal and to select a first encoding mode for encoding the current frame; a mode buffer to store a second encoding mode for encoding the previous frame with respect to the current frame of the input signal; and a speech encoding unit to encode the current frame of the input signal based on the first encoding mode for the current frame selected by the mode selection unit and the second encoding mode for the previous frame outputted from the mode buffer; an audio encoding unit to encode the current frame of the input signal based on the first encoding mode for the current frame selected by the mode selection unit and the second encoding mode for the previous frame outputted from the mode buffer; an input buffer to output the previous frame of the input signal, and wherein the first encoding mode and the second encoding mode is either a Code Excitation Linear Prediction (CELP) scheme or a Modified Discrete Cosine Transform (MDCT) scheme, wherein the speech encoding unit comprises an encoding initialization unit and a first speech encoder, wherein the encoding initialization unit to determine an initial value used for encoding by the first speech encoder, when the first encoding mode is different from the second encoding mode for the previous frame which is MDCT scheme, wherein the first speech encoder to encode the current frame according to the CELP scheme using previous information for the previous frame, when the first encoding mode is identical to the second encoding mode which is the CELP scheme, wherein the first speech encoder to encode the current frame according to the CELP scheme using the initial value outputted from the encoding initialization unit, when the first encoding mode is different from the second encoding mode which is MDCT scheme, wherein the audio encoding unit comprise a second speech encoder, a second audio encoder, a first audio encoder, wherein the first audio encoder to encode the current frame of the input signal based on MDCT scheme, when the first encoding mode is identical to the second encoding mode for the previous frame as the MDCT scheme, wherein, when the first encoding mode is different from the second encoding mode for the previous frame which is CELP scheme, the second speech encoder encodes current frame of the input signal corresponding to a first 1/2 frame of the current frame based on the CELP scheme and, subsequently, the second audio encoder encodes the entire current frame using the MDCT scheme.