Claims

1. An apparatus (70, 300) for decoding audio signal information (12, 12', 12") associated to an audio signal divided in a sequence of frames, comprising:

a bitstream reader (71 , 320) configured to read encoded audio signal information (12, 12', 12", 310) having:

an encoded representation (16a, 17a, 18a, 310) of the audio signal (1 1 ) for a first frame (16, 16', 16") and a second frame (17, 17', 17");

a first pitch information (16b) for the first frame (16, 16', 16") and a first control data item (16c) having a first value; and

a second pitch information (17b) for the second frame (17, 17', 17") and a second control data item (17c) having a second value being different from the first value; and

a controller (72) configured to control a long term post filter, LTPF, (73, 376) to:

filter a decoded representation (71 a, 372) of the audio signal in the second frame (17, 17', 17") using the second pitch information (17b) when the second control data item (17c) has the second value; and

deactivate the LTPF (73, 376) for the first frame (16, 16', 16") when the first control data item (16c) has the first value.

2. The apparatus of claim 1 , wherein:

the bitstream reader (71 , 320) is configured to read a third frame (18"), the third frame (18") having a control data item (18e) indicating the presence or absence of the first pitch information (16b) and/or the second pitch information (17b).

3 The apparatus of claim 2, wherein:

the third frame (18") has a format which lacks the first pitch information (16b), the first control data item (16c), the second pitch information (17b), and the second control data item (17c).

4. The apparatus of claim 2 or 3, wherein:

the third control data item (18e) is encoded in one single bit having a value which distinguishes the third frame (18") from the first and second frame (16", 17").

5. The apparatus of any of the preceding claims, wherein:

in the encoded audio signal information, for the first frame (16"), one single bit is reserved for the first control data item (16c) and a fixed data field (16b) is reserved for the first pitch information.

6. The apparatus of any of the preceding claims, wherein:

in the encoded audio signal information, for the second frame (17"), one single bit is reserved for the second control data item (17c) and a fixed data field (17b) is reserved for the second pitch information.

7. The apparatus of any of the preceding claims, wherein:

the first control data item (16c) and the second control data item (17c) are encoded in the same portion or data field in the encoded audio signal information.

8. The apparatus of any of the preceding claims, wherein:

the encoded audio signal information comprises one first signalling bit encoding the third control data item (18e); and,

in case of a value of the third control data item (18e) indicating the presence of the first pitch information (16b) and/or the second pitch information (17b), a second signalling bit encoding the first control data item (16c) and the second control data item (17c).

9. The apparatus of any of the preceding claims, further comprising:

a concealment unit (75, 380) configured to use the first and/or second pitch information (16b, 17b) to conceal a subsequent non-properly decoded audio frame.

10. The apparatus of claim 9, the concealment unit (75, 380) being configured to:

in case of determination of decoding of an invalid frame (S102), check whether pitch information relating a previously correctly decoded frame is stored (S107),

so as to conceal an invalidly decoded frame with a frame obtained using the stored pitch information (S108).

1 1 An apparatus (10, 10') for encoding audio signals (1 1 ), comprising:

a pitch estimator (13) configured to obtain pitch information (13a) associated to a pitch of an audio signal (1 1 );

a signal analyzer (14) configured to obtain harmonicity information (14a, 24a, 24c) associated to the harmonicity of the audio signal (1 1 ); and

a bitstream former (15) configured to prepare encoded audio signal information (12") encoding frames (16", 17", 18") so as to include in the bitstream:

an encoded representation (16a, 17a, 18a) of the audio signal (1 1 ) for a first frame (16"), a second frame (17"), and a third frame (18");

a first pitch information (16b) for the first frame (16") and a first control data item (16c) having a first value;

a second pitch information (17b) for the second frame (17") and a second control data item (17c) having a second value being different from the first value; and

a third control data item (18e) for the first, second and third frame,

wherein the first value (16c) and the second value (17c) depend on a second criteria (600) associated to the harmonicity information (14a, 24a, 24c), and

the first value (16c) indicates a non-fulfilment of the second criteria (600) for the harmonicity of the audio signal (1 1 ) in the first frame (16"), and

the second value (17c) indicates a fulfilment of the second criteria (600) for the harmonicity of the audio signal (1 1 ) in the second frame (17"),

wherein the second criteria (600) comprise at least a condition (S63) which is fulfilled when at least one second harmonicity measurement (24a") is greater than at least one second threshold,

the third control data item (18e) being encoded in one single bit having a value which distinguishes the third frame (18") from the first and second frame (16", 17"), the third frame (18") being encoded in case of non-fulfilment of a first criteria (S61 ) and the first and second frames (16", 17") being encoded in case of fulfilment of the first criteria (S61 ), wherein the first criteria (S61 ) comprise at least a condition which is fulfilled when at least one first harmonicity measurement (24a') is greater than at least one first threshold,

wherein, in the bitstream, for the first frame (16"), one single bit is reserved for the first control data item (16c) and a fixed data field (16b) is reserved for the first pitch information,

wherein, in the bitstream, for the second frame (17"), one single bit is reserved for the second control data item (17c) and a fixed data field (17b) is reserved for the second pitch information, and

wherein, in the bitstream, for the third frame (18"), no bit is reserved for the fixed data field and/or for the first and second control item.

12. The apparatus of claim 11 , wherein the second criteria (600) comprise at least an additional condition which is fulfilled when at least one harmonicity measurement of the previous frame is greater than the at least one additional threshold.

13. The apparatus of any of claims 1 1 or 12, wherein the first and second harmonicity measurements are obtained at different sampling rates.

14. The apparatus of any of claims 1 1 -13, wherein:

the pitch information (13a) comprises a pitch lag information or a processed version thereof.

15. The apparatus of any of claims 1 1 -14, wherein:

the harmonicity information (14a, 24a, 24a', 24a", 24c) comprises at least one of an autocorrelation value and/or a normalized autocorrelation value and/or a processed version thereof.

16. A method (100) for decoding audio signal information associated to an audio signal divided in a sequence of frames, comprising:

reading (S101 ) an encoded audio signal information (12") comprising:

an encoded representation (16a, 17a) of the audio signal (1 1 ) for a first frame (16") and a second frame (17");

a first pitch information (16b) for the first frame (16") and a first control data item (16c) having a first value;

a second pitch information (17b) for the second frame (17") and a second control data item (17c) having a second value being different from the first value,

at the determination that the first control data item (16c) has the first value, using the first pitch information (16b) for a long term post filter, LTPF, and

at the determination of the second value of the second control data item (17c), deactivating the LTPF.

17. The method of claim 16, further comprising:

at the determination that the first or second control data item (16c, 17c) has the first or second value, using the first or second pitch information (16c, 17b) for an error concealment function.

18. A method (60) for encoding audio signal information associated to a signal divided into frames, comprising:

obtaining (S60) measurements (24a, 24a', 24a") from the audio signal;

verifying (S63, S610-S612) the fulfilment of a second criteria (600), the second criteria (600) being based on the measurements (24a, 24a', 24a") and comprising at least one condition which is fulfilled when at least one second harmonicity measurement (24a') is greater than a second threshold;

forming (S64) an encoded audio signal information (12, 12', 12") having frames

(16", 17", 18") including:

an encoded representation (16a, 17a) of the audio signal (1 1 ) for a first frame (16") and a second frame (17") and a third frame (18");

a first pitch information (16b) for the first frame (16") and a first control data item (16c) having a first value and a third control data item (18e);

a second pitch information (17b) for the second frame (17") and a second control data item (17c) having a second value being different from the first value and a third control data item (18e),

wherein the first value (16c) and the second value (17c) depend on the second criteria (600), and the first value (16c) indicates a non-fulfilment of the second criteria (600) on the basis of a harmonicity of the audio signal (1 1) in the first frame (16"), and the second value (17c) indicates a fulfilment of the second criteria (600) on the basis of a harmonicity of the audio signal (11 ) in the second frame (17"),

the third control data item (18e) being one single bit having a value which distinguishes the third frame (18") from the first and second frames (16", 17") in association to the fulfilment of first criteria (S61 ), so as to identify the third frame (18") when the third control data item (18e) indicates the non-fulfilment of the first criteria (S61 ), on the basis of at least one condition which is fulfilled when at least one first harmonicity measurement (24a') is higher than at least one first threshold,

wherein the encoded audio signal information is formed so that, for the first frame (16"), one single bit is reserved for the first control data item (16c) and a fixed data field for the first pitch information (16b), and

wherein the encoded audio signal information is formed so that, for the second frame (17"), one single bit is reserved for the second control data item (17c) and a fixed data field for the second pitch information (17b), and

wherein the encoded audio signal information is formed so that, for the third frame (18"), no bit is reserved for the fixed data field and no bit is reserved for the first control data item (16c) and the second control data item (17c).

19. A method comprising:

encoding an audio signal (1 1 ) according to claim 16 or 17;

transmitting the encoded audio signal information (12, 12', 12") to a decoder or storing the encoded audio signal information;

decoding the audio signal information (12, 12', 12") according to claim 18.

20. A non-transitory memory unit storing instructions which, when executed by a processor, perform a method according to any of claims 16-19.