Method of decoding an encoded stereo audio signal, the encoded stereo audio signal comprising an encoded first combination signal generated based on a combination rule for combining a first channel audio signal and a second channel audio signal of a stereo audio signal, the encoded first combination signal being a real-valued modified discrete cosine transform, MDCT, representation of a downmix signal generated by mid/side coding as the combination rule, an encoded prediction residual signal being an MDCT representation, and bitstream data comprising a complex prediction coefficient and a prediction direction indicator, comprising: decoding the encoded first combination signal to obtain a decoded first combination signal being a decoded downmix signal, and decoding the encoded prediction residual signal to obtain a decoded residual signal; and calculating a decoded stereo audio signal having a decoded first channel signal being a left channel signal of the decoded stereo audio signal, and a decoded second channel signal being a right channel signal of the decoded stereo audio signal using the decoded residual signal, the complex prediction coefficient, the decoded first combination signal, and the prediction direction indicator indicating a prediction direction from a mid signal to a side signal or from a side signal to a mid signal, wherein the prediction direction indicator is a bit in the bitstream data, wherein the calculating comprises: generating a complex downmix signal from the decoded first combination signal, multiplying (1160b,c) the complex downmix signal and the complex prediction coefficient to obtain a result, adding (1161a,b) the result and the decoded residual signal to obtain an inversely predicted signal, and performing an inverse mid/side coding, wherein, in a first state of the prediction direction indicator, the decoded downmix signal represents the mid signal of the inverse mid/side coding and the inversely predicted signal represents the side signal of the inverse mid/side coding, and wherein, in a second state of the prediction direction indicator, the decoded downmix signal represents the side signal of the inverse mid/side coding and the inversely predicted signal represents the mid signal of the inverse mid/side coding, and performing an inverse MDCT, IMDCT, to a result of the inverse mid/side coding to obtain the left channel signal of the decoded stereo audio signal and the right channel signal of the decoded stereo audio signal. decoding the encoded first combination signal to obtain a decoded first combination signal being a decoded downmix signal, and decoding the encoded prediction residual signal to obtain a decoded residual signal; and calculating a decoded stereo audio signal having a decoded first channel signal being a left channel signal of the decoded stereo audio signal, and a decoded second channel signal being a right channel signal of the decoded stereo audio signal using the decoded residual signal, the complex prediction coefficient, the decoded first combination signal, and the prediction direction indicator indicating a prediction direction from a mid signal to a side signal or from a side signal to a mid signal, wherein the prediction direction indicator is a bit in the bitstream data, wherein the calculating comprises: generating a complex downmix signal from the decoded first combination signal, multiplying (1160b,c) the complex downmix signal and the complex prediction coefficient to obtain a result, adding (1161a,b) the result and the decoded residual signal to obtain an inversely predicted signal, and performing an inverse mid/side coding, wherein, in a first state of the prediction direction indicator, the decoded downmix signal represents the mid signal of the inverse mid/side coding and the inversely predicted signal represents the side signal of the inverse mid/side coding, and wherein, in a second state of the prediction direction indicator, the decoded downmix signal represents the side signal of the inverse mid/side coding and the inversely predicted signal represents the mid signal of the inverse mid/side coding, and performing an inverse MDCT, IMDCT, to a result of the inverse mid/side coding to obtain the left channel signal of the decoded stereo audio signal and the right channel signal of the decoded stereo audio signal. generating a complex downmix signal from the decoded first combination signal, multiplying (1160b,c) the complex downmix signal and the complex prediction coefficient to obtain a result, adding (1161a,b) the result and the decoded residual signal to obtain an inversely predicted signal, and performing an inverse mid/side coding, wherein, in a first state of the prediction direction indicator, the decoded downmix signal represents the mid signal of the inverse mid/side coding and the inversely predicted signal represents the side signal of the inverse mid/side coding, and wherein, in a second state of the prediction direction indicator, the decoded downmix signal represents the side signal of the inverse mid/side coding and the inversely predicted signal represents the mid signal of the inverse mid/side coding, and performing an inverse MDCT, IMDCT, to a result of the inverse mid/side coding to obtain the left channel signal of the decoded stereo audio signal and the right channel signal of the decoded stereo audio signal.