Encoding method, encoder, program and recording medium

An encoding method for a sample string derived from an input audio signal in a given interval, the encoding method obtaining a gain code corresponding to gain obtained by a gain update loop processing step of obtaining gain by loop processing, and an integer signal code obtained by encoding a string of integer value samples obtained by dividing each sample in the sample string by the gain;

• wherein the gain update loop processing step comprises:
• a lower limit gain setting step of, when the number of bits or estimated number of bits in a code obtained by encoding a string of integer value samples obtained by dividing each sample in the sample string by gain before an update is greater than a predetermined number B of allocated bits, setting the gain before the update as a lower limit gain gmin and setting the number of bits or estimated number of bits as the number cL of consumed-bits-with-lower-limit-setting;
• an upper limit gain setting step of, when the number of bits or estimated number of bits in a code obtained by encoding a string of integer value samples obtained by dividing each sample in the sample string by gain before an update is smaller than the predetermined number B of allocated bits, setting the gain before the update as an upper limit gain gmax and setting the number of bits or estimated number of bits as the number cU of consumed-bits-at-upper-limit-setting;
• and
• a gain update step of setting a weighted mean of the upper limit gain and the lower limit gain as an updated gain, where a weight based on at least the predetermined number B of allocated bits, the number cL of consumed-bits-at-lower-limit-setting and the number cU of consumed-bits-at-upper-limit-setting is assigned to at least one of the upper limit gain gmax and the lower limit gain gmin.

An encoding method for a sample string derived from an input audio signal in a given interval, the encoding method comprising:

• a quantization step of quantizing a value obtained by diving each sample in the sample string by gain to obtain a quantized normalized sample string;
• a variable-length encoding step of encoding the quantized normalized sample string by variable-length encoding to obtain a sample string code;
• a gain expansion update step of setting a value greater than the gain as new gain;
• a gain reduction update step of setting a value smaller than the gain as new gain;
• and
• a determination step of, when the number of updates of the gain is equal to a predetermined number of updates, outputting the gain and the sample string code, when the number of updates of the gain is less than the predetermined number of updates and the number of consumed bits which is the number of bits in the sample string code is greater than a predetermined number of allocated bits, causing the gain expansion update step to be performed, and when the number of updates of the gain is less than the predetermined number of updates and the number of the consumed bits is smaller than the predetermined number of allocated bits, causing the gain reduction update step to be performed;
• wherein the gain expansion update step comprises:
• a lower limit gain setting step of, when the number of the consumed bits is greater than the predetermined number of allocated bits, setting a value of gain corresponding to the number of the consumed bits as a lower limit of gain;
• and
• a gain expansion step of, when the number of the consumed bits is greater than the predetermined number of allocated bits and an upper limit of the gain has not been set, updating a value of the gain so that the greater a value of A−T, the greater amount by which the value of the gain before the update increases to a value of updated gain, and causing the quantization step to be performed, where the value of A−T represents the number A of some or all of the samples in the quantized normalized sample string minus the number T of quantized normalized samples corresponding to a truncated sample string code left after removing a truncation code corresponding to amount by which the number of the consumed bits exceeds the predetermined number of allocated bits from the sample string code;
• and
• the gain reduction update step comprises:
• an upper limit gain setting step of, when the number of the consumed bits is smaller than the predetermined number of allocated bits, setting a value of gain corresponding to the number of the consumed bits as an upper limit of gain;
• and
• a gain reduction step of, when the number of the consumed bits is smaller than the predetermined number of allocated bits and a lower limit of the gain has not been set, updating the value of the gain so that the greater the predetermined number of allocated bits minus the number of the consumed bits, the greater amount by which the value of the gain before the update decreases to an updated value, and causing the quantization step to be performed.

An encoding method for a sample string derived from an input audio signal in a given interval, the encoding method comprising:

• a quantization step of quantizing a value obtained by dividing each sample in the sample string by gain to obtain a quantized normalized sample string;
• a gain expansion update step of setting a value greater than the gain as new gain;
• a gain reduction update step of setting a value smaller than the gain as new gain;
• a variable-length encoding step of encoding the quantized normalized sample string by variable-length encoding to obtain a sample string code;
• and
• a determination step of, when the number of updates of the gain is equal to a predetermined number of updates, causing the variable-length encoding step to be performed, when the number of updates of the gain is less than the predetermined number of updates and the number of consumed bits which is an estimated number of bits in a code corresponding to the quantized normalized sample string is greater than a predetermined number of allocated bits, causing the gain expansion update step to be performed, and when the number of updates of the gain is less than the predetermined number of updates and the number of the consumed bits is smaller than the predetermined number of allocated bits, causing the gain reduction update step to be performed;
• wherein the gain expansion update step comprises:
• a lower limit gain setting step of, when the number of the consumed bits is greater than the predetermined number of allocated bits, setting a value of gain corresponding to the number of the consumed bits as a lower limit of gain;
• and
• a gain expansion step of, when the number of the consumed bits is greater than the predetermined number of allocated bits and an upper limit of the gain has not been set, updating a value of the gain so that the greater a value of A−T, the greater amount by which the value of the gain before the update increases to an updated value, and causing the quantization step to be performed, where the value of A−T represents the number A of some or all of the samples in the quantized normalized sample string minus the number T of samples left after removing quantized normalized samples from the quantized normalized sample string, the quantized normalized samples directed to truncation code corresponding to amount by which the number of the consumed bits exceeds the predetermined number of allocated bits;
• and
• the gain reduction update step comprises:
• an upper limit gain setting step of, when the number of the consumed bits is smaller than the predetermined number of allocated bits, setting a value of gain corresponding to the number of the consumed bits as an upper limit of gain;
• and
• a gain reduction step of, when the number of the consumed bits is smaller than the predetermined number of allocated bits and a lower limit of the gain has not been set, updating the value of the gain so that the greater the predetermined number of allocated bits minus the number of the consumed bits, the greater amount by which the value of the gain before the update decreases to an updated value, and causing the quantization step to be performed.

An encoding method for a sample string derived from an input audio signal in a given interval, the encoding method comprising:

• a quantization step of quantizing a value obtained by dividing each sample in the sample string by gain to obtain a quantized normalized sample string;
• a variable-length encoding step of encoding the quantized normalized sample string by variable-length encoding to obtain a sample string code;
• a gain expansion update step of setting a value greater than the gain as new gain;
• a gain reduction update step of setting a value smaller than the gain as new gain;
• and
• a determination step of, when the number of updates of the gain is equal to a predetermined number of updates, outputting the gain and the sample string code, when the number of updates of the gain is less than the predetermined number of updates and the number of consumed bits which is the number of bits in the sample string code is greater than a predetermined number of allocated bits, causing the gain expansion update step to be performed, and when the number of updates of the gain is less than the predetermined number of updates and the number of the consumed bits is less than the predetermined number of allocated bits, causing the gain reduction update step to be performed;
• wherein the gain expansion update step comprises:
• a lower limit gain setting step of, when the number of the consumed bits is greater than the predetermined number of allocated bits, setting a value of gain corresponding to the number of the consumed bits as a lower limit of gain;
• and
• a gain expansion step of, when the number of the consumed bits is greater than the predetermined number of allocated bits and an upper limit of the gain has not been set, updating a value of the gain so that the greater the number of the consumed bits minus the predetermined number of allocated bits, the greater amount by which the value of the gain before the update increases to an updated value, and causing the quantization step to be performed;
• and
• the gain reduction update step comprises:
• an upper limit gain setting step of, when the number of the consumed bits is smaller than the predetermined number of allocated bits, setting a value of gain corresponding to the number of the consumed bits as an upper limit of gain;
• and
• a gain reduction step of, when the number of the consumed bits is smaller than the predetermined number of allocated bits and a lower limit of the gain has not been set, updating the value of the gain so that the greater the predetermined number of allocated bits minus the number of the consumed bits, the greater amount by which the value of the gain before the update decreases to an updated value, and causing the quantization step to be performed.

An encoding method for a sample string derived from an input audio signal in a given interval, the encoding method comprising:

• a quantization step of quantizing a value obtained by dividing each sample in the sample string by gain to obtain a quantized normalized sample string;
• a gain expansion update step of setting a value greater than the gain as new gain;
• a gain reduction update step of setting a value smaller than the gain as new gain;
• and
• a determination step of, when the number of updates of the gain is equal to a predetermined number of updates, causing a variable-length encoding step to be performed, when the number of updates of the gain is less than the predetermined number of updates and the number of consumed bits which is an estimated number of bits in a code corresponding to the quantized normalized sample string is greater than a predetermined number of allocated bits, causing the gain expansion update step to be performed, and when the number of updates of the gain is less than the predetermined number of updates and the number of the consumed bits is smaller than the predetermined number of allocated bits, causing the gain reduction update step to be performed;
• wherein the gain expansion update step comprises:
• a lower limit gain setting step of when the number of the consumed bits is greater than the predetermined number of allocated bits, setting a value of gain corresponding to the number of the consumed bits as a lower limit of gain;
• and
• a gain expansion step of, when the number of the consumed bits is greater than the predetermined number of allocated bits and an upper limit of the gain has not been set, updating the value of gain so that the greater the number of the consumed bits minus the predetermined number of allocated bits, the greater amount by which a value of the gain before the update decreases to an updated value, and causing the quantization step to be performed;
• the gain reduction update step comprises:
• an upper limit gain setting step of, when the number of the consumed bits is smaller than the predetermined number of allocated bits, setting a value of gain corresponding to the number of the consumed bits as an upper limit of gain;
• a gain reduction step of, when the number of the consumed bits is smaller than the predetermined number of allocated bits and a lower limit of the gain has not been set, updating the value of the gain so that the greater the predetermined number of allocated bits minus the number of the consumed bits, the greater amount by which the value of the gain before the update increases to an updated value;
• and
• a variable-length encoding step of encoding the quantized normalized sample string by variable-length encoding to obtain a sample string code.

An encoder encoding a sample string derived from an input audio signal in a given interval, the encoder obtaining a gain code corresponding to gain obtained by a gain update loop processor obtaining gain by loop processing, and an integer signal code obtained by encoding a string of integer value samples obtained by dividing each sample in the sample string by the gain;

• wherein the gain update loop processor comprises:
• a lower limit gain setter that, when the number of bits or estimated number of bits in a code obtained by encoding a string of integer value samples obtained by dividing each sample in the sample string by gain before an update is greater than the predetermined number B of allocated bits, sets the gain before the update as a lower limit gain gmin and sets the number of bits or estimated number of bits as the number cL of consumed bits with lower limit setting;
• an upper limit gain setter that, when the number of bits or estimated number of bits in a code obtained by encoding a string of integer value samples obtained by dividing each sample in the sample string by gain before an update is smaller than the predetermined number B of allocated bits, sets the gain before the update as an upper limit gain gmax and setting the number of bits or estimated number of bits as the number cU of consumed-bits with-upper-limit-setting;
• and
• a gain updater setting a weighted mean of the upper limit gain and the lower limit gain as an updated gain, where a weight based on at least the predetermined number B of allocated bits, the number cL of consumed-bits-at-lower-limit-setting and the number cU of consumed-bits-at-upper-limit-setting is assigned to at least one of the upper limit gain gmax and the lower limit gain gmin.

An encoder encoding a sample string derived from an input audio signal in a given interval, the encoder comprising:

• a quantizer quantizing a value obtained by dividing each sample in the sample string by gain to obtain a quantized normalized sample string;
• a variable-length encoder encoding the quantized normalized sample string by variable-length encoding to obtain a sample string code;
• a gain expansion updater setting a value greater than the gain as new gain;
• a gain reduction updater setting a value smaller than the gain as new gain;
• and
• a determiner that, when the number of updates of the gain is equal to a predetermined number of updates, outputs the gain and the sample string code, when the number of updates of the gain is less than the predetermined number of updates and the number of consumed bits which is the number of bits in the sample string is greater than a predetermined number of allocated bits, causes the gain expansion updater to perform processing, and when the number of updates of the gain is less than the predetermined number of updates and the number of the consumed bits is smaller than the predetermined number of allocated bits, causes the gain reduction updater to perform processing;
• wherein the gain expansion updater comprises:
• a lower limit gain setter that, when the number of the consumed bits is greater than the predetermined number of allocated bits, sets a value of gain corresponding to the number of the consumed bits as a lower limit of gain;
• and
• a gain expander that, when the number of the consumed bits is greater than the predetermined number of allocated bits and an upper limit of the gain has not been set, updates a value of the gain so that the greater a value of A−T, the greater amount by which the value of the gain before the update increases to an updated gain, and causes the quantizer to perform processing, where the value of A−T represents the number A of some or all of the samples in the quantized normalized sample string minus the number T of quantized normalized samples corresponding to a truncated sample string code left after removing a truncation code corresponding to amount by which the number of the consumed bits exceeds the predetermined number of allocated bits from the sample string code;
• and
• the gain reduction updater comprises:
• an upper limit gain setter that, when the number of the consumed bits is smaller than the predetermined number of allocated bits, sets a value of gain corresponding to the number of the consumed bits as an upper limit of gain;
• and
• a gain reducer that, when the number of the consumed bits is smaller than the predetermined number of allocated bits and a lower limit of the gain has not been set, updates the value of the gain so that the greater the predetermined number of allocated bits minus the number of the consumed bits, the greater amount by which the value of the gain before the update decreases to an updated value, and causes the quantizer to perform processing.

An encoder encoding a sample string derived from an input audio signal in a given interval, the encoder comprising:

• a quantizer quantizing a value obtained by dividing each sample in the sample string by gain to obtain a quantized normalized sample string;
• a gain expansion updater setting a value greater than the gain as new gain;
• a gain reduction updater setting a value smaller than the gain as new gain;
• a variable-length encoder encoding the quantized normalized sample string by variable-length encoding to obtain a sample string code;
• and
• a determiner that, when the number of updates of the gain is equal to a predetermined number of updates, causes the variable-length encoder to perform processing, when the number of updates of the gain is less than the predetermined number of updates and the number of consumed bits which is an estimated number of bits in a code corresponding to the quantized normalized sample string is greater than a predetermined number of allocated bits, causes the gain expansion updater to perform processing, and when the number of updates of the gain is less than the predetermined number of updates and the number of the consumed bits is smaller than the predetermined number of allocated bits, causes the gain reduction updater to perform processing;
• wherein the gain expansion updater comprises:
• a lower limit gain setter that, when the number of the consumed bits is greater than the predetermined number of allocated bits, sets a value of gain corresponding to the number of the consumed bits as a lower limit of gain;
• and
• a gain expander that, when the number of the consumed bits is greater than the predetermined number of allocated bits and an upper limit of the gain has not been set, updates a value of the gain so that the greater a value of A−T, the greater amount by which the value of the gain before the update increases to an updated value, and causes the quantizer to perform processing, where the value of A−T represents the number A of some or all of the samples in the quantized normalized sample string minus the number T of samples left after removing quantized normalized samples from the quantized normalized sample string, the quantized normalized samples directed to truncation code corresponding to amount by which the number of the consumed bits exceeds the predetermined number of allocated bits;
• and
• the gain reduction updater comprises:
• an upper limit gain setter that, when the number of the consumed bits is smaller than the predetermined number of allocated bits, sets a value of gain corresponding to the number of the consumed bits as an upper limit of gain;
• and
• a gain reducer that, when the number of the consumed bits is smaller than the predetermined number of allocated bits and a lower limit of the gain has not been set, updates the value of the gain so that the greater the predetermined number of allocated bits minus the number of the consumed bits, the greater amount by which the value of the gain before the update decreases to an updated value, and causes the quantizer to perform processing.

An encoder encoding a sample string derived from an input audio signal in a given interval, the encoder comprising:

• a quantizer quantizing a value obtained by dividing each sample in the sample string by gain to obtain a quantized normalized sample string;
• a variable-length encoder encoding the quantized normalized sample string by variable-length encoding to obtain a sample string code;
• a gain expansion updater setting a value greater than the gain as new gain;
• a gain reduction updater setting a value smaller than the gain as new gain;
• and
• a determiner that, when the number of updates of the gain is equal to a predetermined number of updates, outputs the gain and the sample string code, when the number of updates of the gain is less than the predetermined number of updates and the number of consumed bits which is the number of bits in the sample string code is greater than a predetermined number of allocated bits, causes the gain expansion updater to perform processing, and when the number of updates of the gain is less than the predetermined number of updates and the number of the consumed bits is less than the predetermined number of allocated bits, causes the gain reduction updater to perform processing;
• wherein the gain expansion updater comprises:
• a lower limit gain setter that, when the number of the consumed bits is greater than the predetermined number of allocated bits, sets a value of gain corresponding to the number of the consumed bits as a lower limit of gain;
• and
• a gain expander that, when the number of the consumed bits is greater than the predetermined number of allocated bits and an upper limit of the gain has not been set, updates a value of the gain so that the greater the number of the consumed bits minus the predetermined number of allocated bits, the greater amount by which the value of the gain before the update increases to an updated value, and causes the quantizer to perform processing;
• and
• the gain reduction updater comprises:
• an upper limit gain setter that, when the number of the consumed bits is smaller than the predetermined number of allocated bits, sets a value of gain corresponding to the number of the consumed bits as an upper limit of gain;
• and
• a gain reducer that, when the number of the consumed bits is smaller than the predetermined number of allocated bits and a lower limit of the gain has not been set, updates the value of the gain so that the greater the predetermined number of allocated bits minus the number of the consumed bits, the greater amount by which the value of the gain before the update decreases to an updated value, and causes the quantizer to perform processing.

An encoder encoding a sample string derived from an input audio signal in a given interval, the encoder comprising:

• a quantizer quantizing a value obtained by dividing each sample in the sample string by gain to obtain a quantized normalized sample string;
• a gain expansion updater setting a value greater than the gain as new gain;
• a gain reduction updater setting a value smaller than the gain as new gain;
• and
• a determiner that, when the number of updates of the gain is equal to a predetermined number of updates, causes a variable-length encoder to perform processing, when the number of updates of the gain is less than the predetermined number of updates and the number of consumed bits which is an estimated number of bits in a code corresponding to the quantized normalized sample string is greater than a predetermined number of allocated bits, causes the gain expansion updater to perform processing, and when the number of updates of the gain is less than the predetermined number of updates and the number of the consumed bits is smaller than the predetermined number of allocated bits, causes the gain reduction updater to perform processing;
• wherein the gain expansion updater comprises:
• a lower limit gain setter that, when the number of the consumed bits is greater than the predetermined number of allocated bits, sets a value of gain corresponding to the number of the consumed bits as a lower limit of gain;
• and
• a gain expander that, when the number of the consumed bits is greater than the predetermined number of allocated bits and an upper limit of the gain has not been set, updates a value of the gain so that the greater the number of the consumed bits minus the predetermined number of allocated bits, the greater amount by which the value of the gain before the update increases to an updated value, and causes the quantizer to perform processing;
• and
• the gain reduction updater comprises:
• an upper limit gain setter that, when the number of the consumed bits is smaller than the predetermined number of allocated bits, sets a value of gain corresponding to the number of the consumed bits as an upper limit of gain;
• a gain reducer that, when the number of the consumed bits is smaller than the predetermined number of allocated bits and a lower limit of the gain has not been set, updates the value of the gain so that the greater the predetermined number of allocated bits minus the number of the consumed bits, the greater amount by which the value of the gain before the update decreases to an updated value;
• and
• a variable-length encoder encoding the quantized normalized sample string by variable-length encoding to obtain a sample string code.