Transition from a transform coding/decoding to a predictive coding/decoding

1. A decoding method for decoding a digital audio signal, comprising the following acts performed by a decoding device:

receiving the digital audio signal;

decoding according to an inverse transform decoding of a previous frame of samples of the digital signal, received and coded according to a transform coding;

decoding according to a predictive decoding of a current frame of samples of the digital signal, received and coded according to a predictive coding, wherein the predictive decoding of the current frame is a transition predictive decoding which does not use any adaptive dictionary arising from the previous frame;

reinitializing at least one state of the predictive decoding to a predetermined default value; and

an overlap-add act, which combines a signal segment synthesized by the predictive decoding of the current frame and a signal segment synthesized by inverse transform decoding, corresponding to a stored segment of the decoding of the previous frame.

2. The decoding method as claimed in claim 1 , wherein the inverse transform decoding has a smaller processing delay than that of the predictive decoding and wherein a first segment of the current frame decoded by the predictive decoding is replaced with a segment arising from the inverse transform decoding of the previous frame, wherein a size of the segment arising from the inverse transform decoding of the previous frame corresponds to a delay shift between the predictive decoding and the inverse transform decoding, and wherein the segment arising from the inverse transform decoding of the previous frame is stored in memory during the decoding of the previous frame.

3. The decoding method as claimed in claim 1 , wherein the signal segment synthesized by inverse transform decoding is corrected before the overlap-add act by application of an inverse window compensating a window previously applied to the signal segment synthesized by inverse transform decoding.

4. The decoding method as claimed in claim 1 , wherein the signal segment synthesized by inverse transform decoding is resampled beforehand at a sampling frequency corresponding to the synthesized signal segment of the current frame.

5. The decoding method as claimed in claim 1 , wherein a state of the predictive decoding is in a list of the following states:

a state memory for a filter for resampling at an internal frequency of the predictive decoding;

state memories for pre-emphasis/de-emphasis filters;

coefficients of a linear prediction filter;

a state memory of a synthesis filter;

a memory of an adaptive dictionary;

a state memory of a low-frequency post-filter;

a quantization memory for fixed dictionary gain.

6. The decoding method as claimed in claim 5 , wherein a calculation of coefficients of a linear prediction filter for the predictive decoding of the current frame is performed by decoding coefficients of a unique filter and by allotting identical coefficients to an end-of-frame linear prediction filter, a middle-of-frame linear prediction filter and a start-of-frame linear prediction filter.

7. The decoding method as claimed in claim 5 , further comprising calculation of coefficients of a linear prediction filter for the predictive decoding of the current frame, which comprises the following acts:

determination of decoded values of coefficients of a middle-of-frame filter by using decoded values of coefficients of an end-of-frame filter and predetermined reinitialization values of coefficients of a start-of-frame filter;

replacement of the predetermined reinitialization values of coefficients of the start-of-frame filter by the determined decoded values of the coefficients of the middle-of-frame filter;

determination of coefficients of a linear prediction filter for the predictive decoding of the current frame by using the determined decoded values of the coefficients of the end-of-frame filter, the middle-of-frame filter and the start-of-frame filter.

8. The decoding method as claimed in claim 5 , wherein coefficients of a start-of-frame linear prediction filter are reinitialized to predetermined values corresponding to average values of long-term prediction filter coefficients and wherein linear prediction coefficients of a linear prediction filter for the predictive decoding of the current frame are determined by using the predetermined values and decoded values of coefficients of an end-of-frame filter.

9. A method for coding a digital audio signal, comprising the following acts performed by a coding device:

coding a previous frame of samples of the digital signal according to a transform coding;

reception of a current frame of samples of the digital signal to be coded according to a predictive coding, wherein the predictive coding of the current frame is a transition predictive coding which does not use any adaptive dictionary arising from the previous frame; and

reinitializing at least one state of the predictive coding to a predetermined default value.

10. The coding method as claimed in claim 9 , wherein coefficients of a linear prediction filter form part of at least one state of the predictive coding and calculation of coefficients of a linear prediction filter for the predictive coding of the current frame is performed by determination of values of coefficients of a single prediction filter, either of middle or of end of frame prediction filter and of allotting of identical values for coefficients of the start-of-frame prediction filter and end-or middle-of-frame prediction filter.

11. The coding method as claimed in claim 10 , wherein at least one state of the predictive coding is coded in a direct manner.

12. The coding method as claimed in claim 9 , wherein coefficients of a linear prediction filter form part of at least one state of the predictive coding and calculation of coefficients of a linear prediction filter for predictive coding of the current frame comprises the following acts:

determination of coded values of coefficients of a middle-of-frame filter by using coded values of coefficients of an end-of-frame filter and predetermined reinitialization values of coefficients of a start-of-frame filter;

replacement of the predetermined reinitialization values of coefficients of the start-of-frame filter by the determined coded values of the coefficients of the middle-of-frame filter;

determination of the coefficients of the linear prediction filter for the predictive coding of the current frame by using the determined coded values of the coefficients of the end-of-frame filter, the middle-of-frame filter and the start-of-frame filter.

13. The coding method as claimed in claim 9 , wherein coefficients of a linear prediction filter form part of at least one state of the predictive coding, coefficients of a start-of-frame linear prediction filter are reinitialized to predetermined values corresponding to average values of long-term prediction filter coefficients and wherein linear prediction coefficients of a linear prediction filter for predictive coding of the current frame are determined by using the predetermined values and coded values of coefficients of an end-of-frame filter.

14. A digital audio signal decoder, comprising:

a processor; and

a non-transitory computer-readable medium comprising instructions stored thereon, which when executed by the processor configure the digital audio signal decoder to perform acts comprising:

an inverse transform decoding a previous frame of samples of the digital signal, received and coded according to a transform coding;

predictive decoding a current frame of samples of the digital signal, received and coded according to a predictive coding, wherein the predictive decoding of the current frame is a transition predictive decoding which does not use any adaptive dictionary arising from the previous frame;

reinitializing at least one state of the predictive decoding by a predetermined default value; and

performing an overlap-add which combines a signal segment synthesized by predictive decoding of the current frame and a signal segment synthesized by inverse transform decoding, corresponding to a stored segment of the decoding of the previous frame.

15. A digital audio signal coder, comprising:

a processor; and

a non-transitory computer-readable medium comprising instructions stored thereon, which when executed by the processor configure the digital audio signal coder to perform acts comprising:

transform coding a previous frame of samples of the digital signal;

predictive coding a current frame of samples of the digital signal, wherein the predictive coding of the current frame is a transition predictive coding which does not use any adaptive dictionary arising from the previous frame; and

reinitializing at least one state of the predictive coding by a predetermined default value.

16. A non-transitory computer-readable medium comprising a computer program stored thereon having instructions for execution of a decoding method when the instructions are executed by a processor of a decoding device, wherein the instructions configure the decoding device to perform acts of:

receiving a digital audio signal;

decoding according to an inverse transform decoding of a previous frame of samples of the digital audio signal, received and coded according to a transform coding;

decoding according to a predictive decoding of a current frame of samples of the digital signal, received and coded according to a predictive coding, wherein the predictive decoding of the current frame is a transition predictive decoding which does not use any adaptive dictionary arising from the previous frame;

reinitializing at least one state of the predictive decoding to a predetermined default value; and

an overlap-add act, which combines a signal segment synthesized by the predictive decoding of the current frame and a signal segment synthesized by inverse transform decoding, corresponding to a stored segment of the decoding of the previous frame.