Quality and rate control strategy for digital audio

A computer-readable medium encoded with computer-executable instructions for causing a computer programmed thereby to perform a method of controlling quality and bitrate in an audio encoder, the method comprising:

• determining one or more target quality parameters, a first target quality parameter of the one or more target quality parameters indicating an acceptable audio quality;
• determining plural target bitrate parameters, a first target bitrate parameter of the plural target bitrate parameters indicating a minimum acceptable number of bits produced, and a second target bitrate parameter of the plural target bitrate parameters indicating a maximum acceptable number of bits produced;
• compressing audio information, wherein quantization of the audio information is based at least in part upon the first target quality parameter, the first target bitrate parameter, and the second target bitrate parameter.

In an audio encoder, a computer-implemented method comprising:

• computing a value of a control parameter for a block of spectral audio information, wherein the control parameter is based at least in part upon one or more complexity estimate noise measures;
• and
• quantizing the block, wherein the value of the control parameter at least in part regulates the quantizing.

An audio encoder comprising:

• means for computing a value of a control parameter for audio information, wherein the control parameter is based at least in part upon one or more reliability measures for complexity estimates;
• and
• a quantizer for quantizing the audio information, wherein the value of the control parameter at least in part regulates the quantizer.

A computer-readable medium encoded with computer-executable instructions for causing a computer programmed thereby to perform a method comprising:

• adjusting quantization of a block of frequency coefficients for audio information in a quality control quantization loop until satisfaction of one or more quality criteria;
• and
• following and outside the quality control quantization loop, adjusting the quantization of the block in a bitrate control quantization loop until satisfaction of one or more bitrate criteria.

A computer-readable medium encoded with computer-executable instructions for causing a computer programmed thereby to perform a method comprising:

• selecting a quantization level within a range of quantization levels, wherein the selecting accounts for non-monotonicity of quality measure as a function of quantization level within the range;
• and
• quantizing audio information by the quantization level.

In an audio encoder, a computer-implemented method comprising:

• determining a first bit count associated with a first quantization level;
• determining a second bit count associated with a second quantization level;
• determining a third quantization level within a quantization level range based upon location of a target bitrate on a trajectory of bit count as a function of quantization level, wherein the first and second quantization levels define endpoints of the quantization level range, wherein the first and second bit counts define endpoints of the trajectory, and wherein the function relates bit count in proportion to inverse logarithm of quantization level.

In an audio encoder, a computer-implemented method comprising:

• determining a first quality measure associated with a first quantization level;
• determining a second quality measure associated with a second quantization level;
• determining a third quantization level within a quantization level range based upon location of a target quality on a trajectory of quality measure as a function of quantization level, wherein the first and second quantization levels define endpoints of the quantization level range, wherein the first and second quality measures define endpoints of the trajectory, and wherein the function relates logarithm of quality measure in proportion to inverse logarithm of quantization level.

In an audio encoder, a computer-implemented method comprising:

• in a quality control quantization loop iteration, selecting a first uniform, scalar quantization step size using a first set of rules and quantizing audio information using the first uniform, scalar quantization step size;
• and
• in a bit-count control quantization loop iteration, selecting a second uniform, scalar quantization step size using a second set of rules and quantizing the audio information using the second uniform, scalar quantization step size, wherein the second set of rules is different than the first set of rules.

A computer-readable medium encoded with computer-executable instructions for causing a computer programmed thereby to perform a method comprising:

• computing a value of a control parameter for a block of audio information;
• and
• filtering the value as part of a sequence of previously computed values of the control parameter, wherein the filtered value of the control parameter is for regulating at least in part quantization of the block of audio information.

A computer-readable medium encoded with computer-executable instructions for causing a computer programmed thereby to perform a method comprising:

• comparing a desired buffer fullness level to a current buffer fullness level;
• correcting bias in a model by adjusting a value of a control parameter for a block of audio information based at least in part upon a result of the comparing, wherein the adjusted value of the control parameter is for regulating at least in part quantization of a subsequent block of audio information.

An audio encoder comprising:

• a virtual buffer for storing bits for one or more blocks of frequency coefficients, the virtual buffer having a current fullness level and a desired fullness level;
• and
• means for correcting model bias by adjusting a value of a control parameter based at least in part upon a result of comparing the desired fullness level to the current fullness level, wherein the adjusted value is for regulating at least in part subsequent quantization.