ARBITRARY AVERAGE DATA RATES FOR VARIABLE RATE CODERS

• US 20070171931A1
• Filed: 01/22/2007
• Published: 07/26/2007
• Est. Priority Date: 01/20/2006
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Manjunath, Sharath, Kandhadai, Ananthapadmanabhan
• Granted Patent: US 8,032,369 B2
• Time in Patent Office: Days
• US Class Current: 370/435
• CPC Class Codes: G10L 19/22 Mode decision, i.e. based on audio signal content versus external parameters
• 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

Methods and apparatus are provided for achieving an arbitrary average data rate for a variable rate coder. One method includes selecting a set (e.g., a pair) of initial composite rates surrounding the arbitrary average data rate. A reallocation fraction is then calculated based on the initial composite rates. The reallocation fraction is used to reassign a number of frames from one component rate of an initial composite rate to another in order to achieve the arbitrary average data rate. Such a method may be configured such that selecting an initial composite rate on one side of (e.g., less than) the arbitrary average data rate implicitly selects the initial composite rate on the other side of the arbitrary average data rate.

Claims

1. A method for achieving an arbitrary average data rate for a variable rate coder, comprising:

selecting a first composite rate less than the arbitrary average data rate;

selecting a second composite rate greater than the arbitrary average data rate;

calculating a reallocation fraction based on the first and second composite rates; and

based on the reallocation fraction, reassigning a plurality of frames assigned to a first component rate of the first composite rate to a second component rate of the first composite rate, wherein the second component rate is different than the first component rate.

2. The method of claim 1, wherein said reassigning comprises:

using the reallocation fraction to calculate a reallocation number;

identifying a subset of frames assigned to the first component rate, wherein the size of the subset corresponds to the reallocation number; and

encoding the audio contents of the subset of frames at the second component rate.

3. The method of claim 2, wherein said identifying the subset of frames is performed deterministically.

4. The method of claim 2, wherein said identifying the subset of frames comprises:

obtaining a value of a random variable;

for a frame assigned to the first component rate, evaluating a relation between the obtained value and a threshold based on the reallocation fraction;

according to a result of said evaluating, identifying the frame assigned to the first component rate as a member of the subset.

5. The method of claim 1, wherein the reallocation fraction is calculated according to the expression:

f=(r_T−

r_i)/(r_j−

r_i),

wherein r_T is the arbitrary average rate, r_i is the first initial rate, r_j is the second initial rate, and r_i<

r_T<

r_j.

6. The method according to claim 1, wherein said method comprises:

encoding the plurality of reassigned frames;

calculating an average rate of a sequence of encoded frames that includes the plurality of reassigned frames; and

calculating a second value for the reallocation fraction based on the first and second composite rates, the arbitrary average data rate, and the calculated average rate.

7. A computer program product comprising computer-readable medium comprising:

code for causing at least one computer to select a first composite rate less than the arbitrary average data rate;

code for causing at least one computer to select a second composite rate greater than the arbitrary average data rate;

code for causing at least one computer to calculate a reallocation fraction based on the first and second composite rates; and

code for causing at least one computer to reassign, based on the reallocation fraction, a plurality of frames assigned to a first component rate of the first composite rate to a second component rate of the first composite rate, wherein the second component rate is different than the first component rate.

8. An apparatus for achieving an arbitrary average data rate for a variable rate coder, said apparatus comprising:

a rate selector configured to select a first composite rate less than the arbitrary average data rate and a second composite rate greater than the arbitrary average data rate;

a calculator configured to calculate a reallocation fraction based on the first and second composite rates; and

a frame reassignment module configured to reassign, based on the reallocation fraction, a plurality of frames assigned to a first component rate of the first composite rate to a second component rate of the first composite rate, wherein the second component rate is different than the first component rate.

9. The apparatus according to claim 8, wherein said apparatus comprises circuitry configured to transmit encoded frames to a network for cellular radio-frequency communications.

10. A method for achieving an arbitrary capacity for a network, comprising:

determining a capacity operating point for the network;

setting an arbitrary average data rate for a set of devices accessing the network, the arbitrary average data rate being set in accordance with the capacity operating point;

selecting first and second initial composite rates surrounding the arbitrary average data rate;

based on the selected initial composite rates, calculating a reallocation fraction;

instructing at least one of the set of devices to reassign, based on the reallocation fraction, a plurality of frames assigned to a first component rate of the first composite rate to a second component rate of the first composite rate, wherein the second component rate is different than the first component rate.

11. A method for encoding frames according to a target rate, said method comprising:

selecting a composite rate from among a set of composite rates, wherein each of the set of composite rates includes a first allocation of frames to a first component rate of the selected composite rate and a second allocation of frames to a second component rate of the selected composite rate;

based on the target rate and the selected composite rate, calculating a reallocation fraction;

based on the reallocation fraction and the first allocation of the selected composite rate, reallocating a plurality of frames from the first component rate of the selected composite rate to the second component rate of the selected composite rate.

12. The method according to claim 11, wherein said calculating a reallocation fraction is based on a second composite rate, and

wherein one among the selected composite rate and the second composite rate is greater than the target rate and the other among the selected composite rate and the second composite rate is less than the target rate.

13. The method according to claim 11, wherein said calculating a reallocation fraction is based on an average rate over a plurality of past frames.

14. The method according to claim 11, wherein said selecting a composite rate is based on the target rate.

15. The method according to claim 11, wherein the selected composite rate includes a rate pattern, and wherein said reallocating a plurality of frames includes altering at least one instance of the rate pattern.

16. The method according to claim 11, wherein said method comprises:

encoding the plurality of reallocated frames;

calculating an average rate of a sequence of encoded frames that includes the plurality of reallocated frames; and

calculating a second value for the reallocation fraction based on the first and second composite rates, the target rate, and the calculated average rate.

17. A computer program product comprising computer-readable medium comprising:

code for causing at least one computer to select a composite rate from among a set of composite rates, wherein each of the set of composite rates includes a first allocation of frames to a first component rate of the selected composite rate and a second allocation of frames to a second component rate of the selected composite rate;

code for causing at least one computer to calculate a reallocation fraction based on the target rate and the selected composite rate;

code for causing at least one computer to reallocate, based on the reallocation fraction and the first allocation of the selected composite rate, frames from the first component rate of the selected composite rate to the second component rate of the selected composite rate.

18. An apparatus for encoding frames according to a target rate, said apparatus comprising:

a rate selector configured to select a composite rate from among a set of composite rates, wherein each of the set of composite rates includes a first allocation of frames to a first component rate of the selected composite rate and a second allocation of frames to a second component rate of the selected composite rate;

a calculator configured to calculate a reallocation fraction based on the target rate and the selected composite rate; and

a frame reassignment module configured to reassign, based on the reallocation fraction and the first allocation of the selected composite rate, frames from the first component rate of the selected composite rate to the second component rate of the selected composite rate.

19. The apparatus according to claim 18, wherein said rate selector is configured to select the composite rate based on the target rate.

20. The apparatus according to claim 18, wherein said apparatus comprises a capacity operating point tuner including said rate selector and said calculator.

21. The apparatus according to claim 18, wherein the selected composite rate includes a rate pattern, and

wherein said frame reassignment module is a pattern modifier configured to reassign frames by altering at least one instance of the rate pattern.

22. The apparatus according to claim 18, wherein said frame reassignment module includes a modulo counter,

wherein the frame reassignment module is configured to change a count of the modulo counter using a value based on the reallocation fraction, and

wherein, for each of a plurality of frames, the frame reassignment module is configured to decide whether to reassign the frame based on a rollover of the modulo counter.

23. The apparatus according to claim 18, wherein said apparatus comprises:

a speech encoder configured to encode the reassigned frames at the second component rate; and

circuitry configured to transmit the encoded frames to a network for cellular radio-frequency communications.