Parametric stereo upmix apparatus, a parametric stereo decoder, a parametric stereo downmix apparatus, a parametric stereo encoder
A parametric stereo upmix method for generating a left signal and a right signal from a mono downmix signal based on spatial parameters includes predicting a difference signal comprising a difference between the left signal and the right signal based on the mono downmix signal scaled with a prediction coefficient. The prediction coefficient is derived from the spatial parameters. The method further includes deriving the left signal and the right signal based on a sum and a difference of the mono downmix signal and said difference signal.
1. A method, comprising:
splitting an input bitstream into a mono bitstream and a parameter bitstream;
extracting a prediction residual bitstream from the input bitstream;
decoding the mono bitstream into a mono downmix signal;
decoding a prediction residual signal from the prediction residual bitstream;
decoding the parameter bitstream into spatial parameters;
scaling the mono downmix signal with a prediction coefficient to produce a scaled mono downmix signal, wherein the prediction coefficient is derived from the spatial parameters;
predicting a difference signal, wherein the difference signal comprises a difference between a left signal and a right signal, wherein the predicting is based on the scaled mono downmix signal;
forming the left signal based on a sum of: the mono downmix signal, the difference signal, and the prediction residual signal; and
forming the right signal based on difference between: (1) the mono downmix signal, and (2) a sum of the difference signal and the prediction residual signal.
2. The method of claim 1 , wherein the prediction coefficient (α) is a function of the spatial parameters as:
α
=
iid
-
1
-
j
·
2
·
sin
(
ipd
)
·
icc
·
iid
iid
+
1
+
2
·
cos
(
ipd
)
·
icc
·
iid
wherein iid, ipd, and icc are the spatial parameters,
wherein iid is an interchannel intensity difference,
wherein ipd is an interchannel phase difference,
wherein icc is an interchannel coherence.
3. The method of claim 1 , further comprising enhancing the difference signal,
wherein the enhancing comprises adding a scaled decorrelated mono downmix signal to the difference signal,
wherein the scaled decorrelated mono downmix signal is formed by scaling a decorrelated mono downmix signal by a scaling factor (β),
wherein the scaling factor is:
β
=
iid
+
1
-
2
·
cos
(
ipd
)
·
icc
·
iid
iid
+
1
+
2
·
cos
(
ipd
)
·
icc
·
iid
-
|
α
|
2
wherein α is the prediction coefficient,
wherein idd is an interchannel intensity difference,
wherein ipd is an interchannel phase difference, and
wherein icc is an interchannel coherence.
4. The method of claim 1 , wherein the prediction residual signal has zero correlation with the mono downmix signal.
5. The method of claim 1 , further comprising enhancing the difference signal,
wherein the enhancing comprises adding a scaled decorrelated mono downmix signal to the difference signal,
wherein the scaled decorrelated mono downmix signal is formed by scaling a decorrelated mono downmix signal by a scaling factor,
wherein the scaling factor compensates for a prediction energy loss.
6. The method of claim 1 , wherein the prediction coefficient is based on waveform matching the downmix signal onto the difference signal.