Advanced stereo coding based on a combination of adaptively selectable left/right or mid/side stereo coding and of parametric stereo coding

1. An encoder system encoding a stereo signal to a bitstream signal, the encoder system comprising:

a downmix stage generating a downmix signal and a residual signal based on the stereo signal;

a parameter determining stage coupled to the downmix stage and determining one or more parametric stereo parameters;

a perceptual encoder coupled downstream to the downmix stage, wherein the perceptual encoder selects

encoding based on a sum of the downmix signal and the residual signal and based on a difference of the downmix signal and the residual signal, or

encoding based on the downmix signal and based on the residual signal in a frequency-variant or frequency-invariant manner.

2. The encoder system of claim 1 , wherein the perceptual encoder comprises:

a transformation stage performing a transform based on the downmix signal and the residual signal, thereby generating a pseudo left/right stereo signal; and

an encoder encoding the pseudo left/right stereo signal, wherein the encoder selects

left/right perceptual encoding or

mid/side perceptual encoding

in a frequency-variant or frequency-invariant manner.

3. The encoder system of claim 2 , wherein the encoder decides between

left/right encoding or

mid/side encoding

in a frequency-variant or frequency-invariant manner based on the pseudo stereo signal.

4. The encoder system of claim 2 , wherein the encoder performs a left/right to mid/side transform based on the pseudo stereo signal.

5. The encoder system of claim 1 , wherein the perceptual encoder comprises

a transformation stage performing a sum and difference transform based on the downmix signal and the residual signal to generate a pseudo left/right stereo signal for one or more or all used frequency bands.

6. The encoder system of claim 5 , wherein

the perceptual encoder comprises a processor deciding between L/R perceptual encoding and M/S perceptual encoding in a frequency-variant or frequency-invariant manner;

encoding based on the downmix signal and residual signal is selected when the processor decides M/S perceptual decoding, and

encoding based on the sum and difference is selected when the processor decides L/R perceptual decoding.

7. The encoder system of claim 1 , wherein the encoder system selects in a frequency-variant or frequency-invariant manner between

parametric stereo encoding the stereo signal to the bitstream signal or

left/right encoding the stereo signal to the bitstream signal.

8. An encoder system encoding a stereo signal to a bitstream signal, the encoder system comprising:

a downmix stage generating a downmix signal and a residual signal based on the stereo signal;

a parameter determining stage coupled to the downmix stage, and determining one or more parametric stereo parameters;

a transform stage coupled to the downmix stage, and performing a transform based on the downmix signal and the residual signal, thereby generating a pseudo left/right stereo signal; and

a perceptual stereo encoder coupled to the downmix stage and encoding the pseudo left/right stereo signal, wherein the perceptual stereo encoder is configured to select

left/right perceptual encoding or

mid/side perceptual encoding

in a frequency-variant or frequency-invariant manner.

9. A decoder system decoding a bitstream signal including one or more parametric stereo parameters to a stereo signal, the decoder system comprising:

a perceptual decoder decoding based on the bitstream signal, wherein the perceptual decoder generating by decoding a first signal and a second signal and outputting a downmix signal and a residual signal, wherein the perceptual decoder selects the downmix signal and the residual signal

based on a sum of the first signal and of the second signal and based on a difference of the first signal and of the second signal or

based on the first signal and based on the second signal

in a frequency-variant or frequency-invariant manner; and

an upmixer coupled to the perceptual decoder, and generating the stereo signal based on the downmix signal and the residual signal, with the upmix operation of the upmixer being dependent on the one or more parametric stereo parameters.

10. The decoder system of claim 9 , wherein the perceptual decoder comprises:

a stereo decoder decoding based on the bitstream signal, the stereo decoder generating a pseudo stereo signal, wherein the stereo decoder selectively performs

left/right perceptual decoding or

mid/side perceptual decoding

in a frequency-variant or frequency-invariant manner; and

a transform stage performing a transform based on the pseudo stereo signal, thereby generating the downmix signal and the residual signal.

11. The decoder system of claim 10 , wherein the perceptual decoder performs a mid/side to left/right transform based on a decoded pseudo mid/side signal.

12. The decoder system of claim 9 , wherein the perceptual decoder comprises:

a transformation stage performing a sum and difference transform based on the first signal and the second signal for one or more or all used frequency bands.

13. The decoder system of claim 12 , wherein

the perceptual decoder comprises a selector selecting between L/R perceptual decoding and M/S perceptual decoding in a frequency-variant or frequency-invariant manner;

the downmix signal and the residual signal is selected to be based on the sum of the first signal and of the second signal and based on the difference of the first signal and of the second signal when the selector selects L/R perceptual decoding, and

the downmix signal and the residual signal is selected to be based on the first signal and based on the second signal when the selector selects M/S perceptual decoding.

14. The decoder system of claim 9 , wherein the decoder system switches in a frequency-variant or frequency-invariant manner between

parametric stereo decoding the bitstream signal to the stereo signal or

left/right decoding the bitstream signal to the stereo signal.

15. The decoder system of claim 9 , wherein the parametric stereo parameters comprise

a frequency-variant or a frequency-invariant parameter indicating a an inter-channel intensity difference, and

a frequency-variant or a frequency-invariant parameter indicating an inter-channel cross-correlation.

16. A decoder system decoding a bitstream signal including one or more parametric stereo parameters to a stereo signal, the decoder system comprising:

a perceptual stereo decoder decoding based on the bitstream signal, the decoder generating a pseudo stereo signal, wherein the decoder selectively performs

left/right perceptual decoding or

mid/side perceptual decoding

in a frequency-variant or frequency-invariant manner;

a left/right to mid/side transformation stage performing a left/right to mid/side transform based on the pseudo stereo signal, thereby generating a downmix signal and a residual signal; and

an upmixer coupled to the perceptual stereo decoder, and generating the stereo signal based on the downmix signal and the residual signal, with the upmix operation of the upmixer being dependent on the one or more parametric stereo parameters.

17. A method for encoding a stereo signal to a bitstream signal, the method comprising:

generating a downmix signal and a residual signal based on the stereo signal;

determining one or more parametric stereo parameters;

perceptual encoding downstream of generating the downmix signal and the residual signal, wherein

encoding based on a sum of the downmix signal and the residual signal and based on a difference of the downmix signal and the residual signal or

encoding based on the downmix signal and based on the residual signal

is selectable in a frequency-variant or frequency-invariant manner;

wherein the method is performed by one or more microprocessor-based components.

18. A method for encoding a stereo signal to a bitstream signal, the method comprising:

generating a downmix signal and a residual signal based on the stereo signal;

determining one or more parametric stereo parameters;

generating a pseudo left/right stereo signal by performing a transform based on the downmix signal and the residual signal; and

performing perceptual stereo encoding of the pseudo left/right stereo signal, wherein

left/right perceptual encoding or

mid/side perceptual encoding

is selectable in a frequency-variant or frequency-invariant manner;

wherein the method is performed by one or more microprocessor-based components.

19. A method for decoding a bitstream signal including one or more parametric stereo parameters to a stereo signal, the method comprising:

perceptual decoding based on the bitstream signal, wherein a first signal and a second signal is generated by decoding and a downmix signal and a residual signal is output after perceptual decoding, the downmix signal and the residual signal being selectively

based on the sum of the first signal and of the second signal and based on the difference of the first signal and of the second signal or

based on the first signal and based on the second signal

in a frequency-variant or frequency-invariant manner; and

generating the stereo signal based on the downmix signal and the residual signal by an upmix operation, with the upmix operation being dependent on the one or more parametric stereo parameters;

wherein the method is performed by one or more microprocessor-based components.

20. A method for decoding a bitstream signal including one or more parametric stereo parameters to a stereo signal, the method comprising:

performing perceptual stereo decoding based on the bitstream signal to generate a pseudo stereo signal, wherein

left/right perceptual decoding or

mid/side perceptual decoding

is selectable in a frequency-variant or frequency-invariant manner;

generating a downmix signal and a residual signal by performing a transform based on the pseudo stereo signal; and

generating the stereo signal based on the downmix signal and the residual signal by an upmix operation, with the upmix operation being dependent on the one or more parametric stereo parameters;

wherein the method is performed by one or more microprocessor-based components.