A device for decoding an audio signal, the device comprising: a receiver configured to receive bitstream parameters corresponding to at least an encoded mid signal; and a decoder configured to: generate a synthesized mid signal based on the bitstream parameters; determine whether the bitstream parameters correspond to an encoded side signal; generate a synthesized side signal from the bitstream parameters independently of the synthesized mid signal in response to determining that the bitstream parameters correspond to an encoded side signal, or generate the synthesized side signal based on the synthesized mid signal in response to determining that the bitstream parameters do not correspond to an encoded side signal; generate an upmix parameter having a first value in response to determining that the bitstream parameters correspond to an encoded side signal, or having a second value in response to determining that the bitstream parameters do not correspond to an encoded side signal, wherein the first value is based on a received downmix parameter and the second value is based at least in part on a default parameter value; and use the upmix parameter to perform upmix processing to generate a first audio output signal and a second audio output signal from the synthesized mid signal and the synthesized side signal. a receiver configured to receive bitstream parameters corresponding to at least an encoded mid signal; and a decoder configured to: generate a synthesized mid signal based on the bitstream parameters; determine whether the bitstream parameters correspond to an encoded side signal; generate a synthesized side signal from the bitstream parameters independently of the synthesized mid signal in response to determining that the bitstream parameters correspond to an encoded side signal, or generate the synthesized side signal based on the synthesized mid signal in response to determining that the bitstream parameters do not correspond to an encoded side signal; generate an upmix parameter having a first value in response to determining that the bitstream parameters correspond to an encoded side signal, or having a second value in response to determining that the bitstream parameters do not correspond to an encoded side signal, wherein the first value is based on a received downmix parameter and the second value is based at least in part on a default parameter value; and use the upmix parameter to perform upmix processing to generate a first audio output signal and a second audio output signal from the synthesized mid signal and the synthesized side signal. generate a synthesized mid signal based on the bitstream parameters; determine whether the bitstream parameters correspond to an encoded side signal; generate a synthesized side signal from the bitstream parameters independently of the synthesized mid signal in response to determining that the bitstream parameters correspond to an encoded side signal, or generate the synthesized side signal based on the synthesized mid signal in response to determining that the bitstream parameters do not correspond to an encoded side signal; generate an upmix parameter having a first value in response to determining that the bitstream parameters correspond to an encoded side signal, or having a second value in response to determining that the bitstream parameters do not correspond to an encoded side signal, wherein the first value is based on a received downmix parameter and the second value is based at least in part on a default parameter value; and use the upmix parameter to perform upmix processing to generate a first audio output signal and a second audio output signal from the synthesized mid signal and the synthesized side signal.