Decoder for decoding an encoded audio signal, the decoder comprising: an adaptive spectrum-time converter for converting successive blocks of spectral values (4', 4") into successive blocks of time values; and an overlap-add-processor for overlapping and adding successive blocks of time values to obtain decoded audio values, wherein the adaptive spectrum-time converter is configured to receive a control information and to switch, in response to the control information, between transform kernels of a first group of transform kernels comprising one or more transform kernels having different symmetries at sides of a kernel, and a second group of transform kernels comprising one or more transform kernels having the same symmetries at sides of a transform kernel, wherein the transform kernel of the first group and the second group is based on the following equation: x i, n = C ∑ k = 0 M − 1 spec i k cs 2 π N n + n 0 k + k 0 wherein the at least one transform kernel of the first group is based on the parameters: cs() = cos() and k 0 = 0.5 or cs() = sin() and k 0 = 0.5, or wherein the at least one transform kernel of the second group is based on the parameters: cs() = cos() and k 0 = 0; or cs() = sin() and k 0 = 1, wherein x i,n is a time domain output, C is a constant parameter, N is a time-window length, spec are spectral values having M values for a block, M is equal to N/2, i is a time block index, k is a spectral index indicating a spectral value, n is a time index indicating a time value in a block i, and n o is a constant parameter being an integer number or zero, and wherein the adaptive spectrum-time converter is configured to apply the transform kernel based on the following table: current frame i → right-side symmetry right-side symmetry previous frame i -1 ↓ even ( symm i = 0) odd ( symm i = 1) right-side symmetry cs(...) = cos(...) cs(...) = sin(...) odd ( symm i -1 = 1) k 0 = 0.0 k 0 = 0.5 right-side symmetry cs(...) = cos(...) cs(...) = sin(...) even ( symm i -1 = 0) k 0 = 0.5 k 0 = 1.0 wherein symm i is the control information for the current frame at index i, and wherein symm i-1 is the control information for the previous frame at index i-1. an adaptive spectrum-time converter for converting successive blocks of spectral values (4', 4") into successive blocks of time values; and an overlap-add-processor for overlapping and adding successive blocks of time values to obtain decoded audio values, wherein the adaptive spectrum-time converter is configured to receive a control information and to switch, in response to the control information, between transform kernels of a first group of transform kernels comprising one or more transform kernels having different symmetries at sides of a kernel, and a second group of transform kernels comprising one or more transform kernels having the same symmetries at sides of a transform kernel, wherein the transform kernel of the first group and the second group is based on the following equation: x i, n = C ∑ k = 0 M − 1 spec i k cs 2 π N n + n 0 k + k 0 wherein the at least one transform kernel of the first group is based on the parameters: cs() = cos() and k 0 = 0.5 or cs() = sin() and k 0 = 0.5, or wherein the at least one transform kernel of the second group is based on the parameters: cs() = cos() and k 0 = 0; or cs() = sin() and k 0 = 1, wherein x i,n is a time domain output, C is a constant parameter, N is a time-window length, spec are spectral values having M values for a block, M is equal to N/2, i is a time block index, k is a spectral index indicating a spectral value, n is a time index indicating a time value in a block i, and n o is a constant parameter being an integer number or zero, and wherein the adaptive spectrum-time converter is configured to apply the transform kernel based on the following table: current frame i → right-side symmetry right-side symmetry previous frame i -1 ↓ even ( symm i = 0) odd ( symm i = 1) right-side symmetry cs(...) = cos(...) cs(...) = sin(...) odd ( symm i -1 = 1) k 0 = 0.0 k 0 = 0.5 right-side symmetry cs(...) = cos(...) cs(...) = sin(...) even ( symm i -1 = 0) k 0 = 0.5 k 0 = 1.0 wherein symm i is the control information for the current frame at index i, and wherein symm i-1 is the control information for the previous frame at index i-1.