Pulse encoding and decoding method and pulse codec

• US 8,959,018 B2
• Filed: 01/08/2014
• Issued: 02/17/2015
• Est. Priority Date: 06/24/2010
• Status: Active Grant

• Current Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Original Assignee: Huawei Technologies Co., Ltd. (Huawei Investment & Holding Co., Ltd.)
• Inventors: Ma, Fuwei, Zhang, Dejun
• Primary Examiner(s): BAKER, MATTHEW H
• Application Number:
  US14/150,498
• Publication Number:
  US 20140122066A1
• Time in Patent Office: 405 Days
• Field of Search: 704/219
• US Class Current: 704/219
• CPC Class Codes: G10L 19/00 Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis in musical instruments G10H
• CPC Class Codes: G10L 19/002 Dynamic bit allocation for perceptual audio coders G10L19/032
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: G10L 19/107 Sparse pulse excitation, e.g. by using algebraic codebook
• CPC Class Codes: G10L 19/12 the excitation function being a code excitation, e.g. in code excited linear prediction [CELP] vocoders
• CPC Class Codes: G10L 19/24 Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding

Abstract

In a pulse encoding and decoding method and a pulse codec, more than two tracks are jointly encoded, so that free codebook space in the situation of single track encoding can be combined during joint encoding to become code bits that may be saved. Furthermore, a pulse that is on each track and required to be encoded is combined according to positions, and the number of positions having pulses, distribution of the positions that have pulses on the track, and the number of pulses on each position that has a pulse are encoded separately, so as to avoid separate encoding performed on multiple pulses of a same position, thereby further saving code bits.

Claims

1. A pulse audio encoding method performed by a pulse encoder which is implemented by hardware, comprising:

obtaining algebraic codebook pulses that are on T tracks and to be encoded, wherein T is an integer greater than or equal to 2;

separately collecting, according to positions, statistics about at least one pulse that is on each track and to be encoded, to obtain the number N_t of positions that have at least one pulse on each track, distribution of the positions that have at least one pulse on each track, and the number of pulses on each position that has at least one pulse, wherein the subscript t represents a t^th track, and tε

[0, T−

1];

according to a {N₀, N₁, . . . , N_T-1} combination of the number of positions that have at least one pulse on the T tracks, determining a first index I1, wherein the first index I1 corresponds to all possible distribution situations of positions that have at least one pulse and are on each track;

determining a second index I2_t of each track separately according to distribution of positions that have at least one pulse and are on each track, wherein the second index indicates, among all possible distribution situations corresponding to the first index I1, a distribution situation which corresponds to distribution of current positions having at least one pulse on a corresponding track;

determining a third index I3_t of each track separately according to the number of pulses on each position that has at least one pulse and is on each track; and

generating a code index Ind, wherein the code index comprises information of the first index, the second index of each track and the third index of each track.

2. The audio encoding method according to claim 1, further comprises:

obtaining, according to a positive or negative feature of a pulse symbol of each position that has at least one pulse and is on each track, pulse symbol information of each position that has at least one pulse and is on each track; and

the code index Ind further comprises information of a symbol index which corresponds to each position that has at least one pulse and is on each track, and the symbol index indicates pulse symbol information which is of a position that has at least one pulse and corresponds to the symbol index.

3. The audio encoding method according to claim 1, wherein:

the first index corresponds to one {N₀, N₁, . . . , N_T-1} combination, or,

the first index corresponds to at least two {N₀, N₁, . . . , N_T-1} combinations, wherein for a track with at least two N_t values corresponding to the first index, an additional index corresponding to the number of current positions that have at least one pulse and are on the track with at least two N_t values is further determined, the additional index corresponds to all possible distribution situations of positions that have at least one pulse and are on the track with at least two N_t values, wherein the number of positions having at least one pulse in the track with at least two N_t values is represented by the additional index, and the code index further comprises information of the additional index.

4. The audio encoding method according to claim 3, wherein the code index Ind is generated by adopting the following manner:

5. The audio encoding method according to claim 1, wherein after generating the code index, the method further comprises:

comparing the code index Ind with an adjustment threshold THR, wherein

THR≦

2^Bmax−

I_max(T),

I_max(T) represents an upper limit value of Ind, and Bmax represents an upper limit value of the number of bits used for encoding the code index; and

when Ind is smaller than THR, code bits, the number of which is a first number, are adopted to encode Ind;

otherwise, code bits, the number of which is a second number, are adopted to encode Ind plus an offset value THR₀, wherein THR≦

THR₀≦

2^Bmax−

I_max(T), the first number is smaller than the second number, the second number is smaller than or equal to Bmax, and the first number and the second number are both positive integers.

6. The audio encoding method according to claim 5, wherein correspondence between the first index and a {N₀, N₁, . . . , N_T-1} combination is determined by adopting the following manner:

collecting statistics about a probability of occurrence of the {N₀, N₁, . . . , N_T-1} combination, to make a first index corresponding to a combination of a higher probability of occurrence be smaller.

7. The audio encoding method according to claim 1, wherein determining a third index I3_t of each track separately according to the number of pulses on each position that has the pulses and is on each track comprises:

for the t^th track, situations that N_t positions having pulses have pulses are mapped to situations that N_t positions have −

N_t pulses, wherein represents the total number of pulses to be encoded on the t^th track; and

according to set order, all possible distribution situations of −

N_t pulses on N_t positions are arrayed, and an arrayed serial number is used as the third index I3_t indicating the number of pulses on a position that has at least one pulse.

8. The audio encoding method according to claim 7, wherein a calculation formula of the third index I3_t of each track is:

9. The audio encoding method according to claim 1, wherein a calculation formula of the second index I2_t of each track is:

10. A pulse audio decoding method performed by a pulse decoder which is implemented by hardware, comprising:

obtaining an algebraic codebook code index Ind, extracting a first index from the code index, and determining, according to the first index, a {N₀, N₁, . . . , N_T-1} combination of the number of positions that have at least one pulse on T tracks, wherein the subscript t of N_t represents a t^th track, tε

[0, T−

1], and T is an integer greater than or equal to 2;

extracting a second index I2_t of the t^th track and a third index I3_t of the t^th track from the code index;

according to the second index, determining distribution of positions that have at least one pulses on the t^th track under the number of positions having at least one pulse on the t^th track, N_t which is determined according to the first index;

according to the third index, determining the number of pulses on each position that has at least one pulse on the t^th track; and

according to distribution of the positions that have at least one pulse on the t^th track and the number of pulses on each position that has at least one pulse, reconstructing a pulse sequence on the t^th track.

11. The audio decoding method according to claim 10, wherein extracting the first index from the code index comprises:

judging a value range to which the code index belongs among several set independent value ranges, and determining the first index according to a starting value corresponding to the value range to which the code index belongs.

12. The audio decoding method according to claim 10, wherein:

the first index corresponds to one {N₀, N₁, . . . , N_T-1} combination, or,

the first index corresponds to at least two {N₀, N₁, . . . , N_T-1} combinations;

for a track with at least two N_t values corresponding to the first index, an additional index corresponding to the number of current positions that have at least one pulse and are on the track with at least two N_t values is further extracted, and the additional index corresponds to all possible distribution situations of positions that have at least one pulse and are on the track with at least two N_t values, wherein the number of positions having at least one pulse in the track with at least two N_t values is represented by the additional index.

13. The audio decoding method according to claim 10, wherein obtaining the code index Ind comprises:

extracting code bits, the number of which is a first number, from an encoded code stream;

when a decoded value of the code bits, the number of which is the first number, is smaller than an adjustment threshold THR, using the decoded value of the code bits as a code index Ind;

otherwise, increasing the number of extracted code bits to a second number, and using a value obtained by subtracting an offset value THR₀ from a decoded value of code bits, the number of which is the second number, as a code index Ind.

14. A pulse audio encoder implemented by hardware comprising:

a pulse statistics unit, configured to obtain algebraic codebook pulses that are on T tracks and to be encoded, wherein T is an integer greater than or equal to 2; and

separately collect, according to positions, statistics about at least one pulse that is on each track and to be encoded, to obtain the number N_t of positions that have at least one pulse on each track, distribution of the positions that have at least one pulse on each track, and the number of pulses on each position that has at least one pulse, wherein the subscript t represents a t^th track, and tε

[0, T−

1];

an index calculation unit, wherein the index calculation unit comprises;

a first index unit, configured to, according to a {N₀, N₁, . . . , N_T-1} combination of the number of positions that have at least one pulse on the T tracks, determine a first index I1, wherein the first index I1 corresponds to all possible distribution situations of positions that have at least one pulse and are on each track;

a second index unit, configured to output a second index I2_t of each track separately according to distribution of positions that have at least one pulses and are on each track, wherein the second index indicates, among all possible distribution situations corresponding to the first index, a distribution situation which corresponds to distribution of current positions having at least one pulse on a corresponding track; and

a third index unit, configured to output a third index I3_t of each track separately according to the number of pulses on each position that has at least one pulse and is on the track; and

an index combination unit, configured to combine information of the first index I1, the second index of each track and the third index of each track to generate a code index Ind.

15. The audio encoder according to claim 14, wherein the first index corresponds to at least two {N₀, N₁, . . . , N_T-1} combinations,

the index calculation unit further comprises an additional index unit, configured to, for a track with at least two N_t values corresponding to the first index, determine an additional index corresponding to the number of current positions that have at least one pulse and are on the track with at least two N_t values, wherein the additional index corresponds to all possible distribution situations of positions that have at least one pulse and are on the track with at least two N_t values, wherein the number of positions having at least one pulse in the track with at least two N_t values is represented by the additional index;

and

the index combination unit further combines information of the additional index into the code index.

16. The audio encoder according to claim 14, further comprising a code bit adjustment unit, configured to compare the code index Ind with an adjustment threshold THR after the index combination unit generates the code index, wherein

THR≦

2^Bmax−

I_max(T),

I_max(T) represents an upper limit value of Ind, and Bmax represents an upper limit value of the number of bits used for encoding the code index; and

when Ind is smaller than THR, code bits, the number of which is a first number, are adopted to encode Ind;

otherwise, code bits, the number of which is a second number, are adopted to encode Ind plus an offset value THR₀, wherein THR≦

THR₀≦

2^Bmax−

I_max(T), the first number is smaller than the second number, the second number is smaller than or equal to Bmax, and the first number and the second number are both positive integers.

17. A pulse audio decoder implemented by hardware executing comprising:

a first extraction unit, configured to obtain an algebraic codebook code index Ind, extract a first index from the code index, and determine, according to the first index, a {N₀, N₁, . . . , N_T-1} combination of the number of positions that have at least one pulse on T tracks, wherein the subscript t of N_t represents a t^th track, tε

[0, T−

1], and T is an integer greater than or equal to 2;

a second extraction unit, configured to extract a second index I2_t of each track and a third index I3_t of each track from the code index;

a first decoding unit, configured to, according to the second index, determine distribution of the positions that have at least one pulse on the t^th track under the number of positions having at least one pulses on the t^th track, N_t which is determined according to the first index;

a second decoding unit, configured to, according to the third index, determine the number of pulses on each position that has at least one pulse on the t^th track; and

a pulse reconstruction unit, configured to, according to distribution of the positions that have at least one pulse on the t^th track and the number of pulses on each position that has at least one pulse, reconstruct a pulse sequence on the t^th track.

18. The audio decoder according to claim 17, wherein the first index corresponds to at least two {N₀, N₁, . . . , N_T-1} combinations, and the decoder further comprises:

an additional extraction unit, configured to, for a track with at least two N_t values corresponding to the first index, extract an additional index corresponding to the number of current positions that have at least one pulse and are on the track with at least two N_t values, wherein the additional index corresponds to all possible distribution situations of positions that have at least one pulse and are on the track with at least two N_t values, wherein the number of positions having at least one pulse is represented by the additional index; and

the second extraction unit extracts the second index I2_t of the track and the third index I3_t of the track according to the number of current positions that have at least one pulse and are on a corresponding track, wherein the number of current positions that have at least one pulse and are on a corresponding track is determined by the additional index extracted by the additional extraction unit.

19. The audio decoder according to claim 17, further comprising a decoding bit adjustment unit, configured to extract code bits, the number of which is a first number, from an encoded code stream;

when a decoded value of the code bits, the number of which is the first number, is smaller than an adjustment threshold THR, use the decoded value of the code bits as a code index Ind for output;

otherwise, increase the number of extracted code bits to a second number, and use a value obtained by subtracting an offset value THR₀ from a decoded value of code bits, the number of which is the second number, as a code index Ind for output.