Audio transcoding method and apparatus comprising performing entropy decoding and entropy coding to obtain a second audio stream with a lower bitrate

1 . An audio transcoding method, performed by a computer device, the method comprising:

performing entropy decoding on a first audio stream with a first bitrate, to obtain an audio feature parameter and an excitation signal of the first audio stream without a complete parameter extraction process, the excitation signal being a quantized audio signal;

obtaining a time-domain audio signal corresponding to the excitation signal based on the audio feature parameter and the excitation signal;

determining a first candidate quantization parameter based on a target transcoding bitrate through at least one iteration process;

simulating a re-quantization process of the excitation signal and the audio feature parameter based on the first candidate quantization parameter to obtain a first signal corresponding to the excitation signal and a first parameter corresponding to the audio feature parameter, wherein simulating the re-quantization process comprises:

respectively simulating a discrete cosine transform process of the excitation signal and a discrete cosine transform process of the audio feature parameter, to obtain a second signal corresponding to the excitation signal and a second parameter corresponding to the audio feature parameter; and

performing rounding after the second signal and the second parameter are respectively divided by the first candidate quantization parameter;

simulating an entropy coding process of the first signal and the first parameter, to obtain an analog audio stream;

identifying the first candidate quantization parameter as a first quantization parameter only in response to the analog audio stream meeting a first target condition and at least one of the time-domain audio signal and a first signal as an intermediate output of the simulation process, the target transcoding bitrate and a bitrate of the analog audio stream, or a number of completed iterations meeting a second target condition, the first quantization parameter being used for adjusting the first bitrate of the first audio stream to the target transcoding bitrate;

re-quantizing the excitation signal and the audio feature parameter based on the time-domain audio signal and the first quantization parameter, to obtain a target excitation signal and a target audio feature parameter; and

performing entropy coding only on the target audio feature parameter and the target excitation signal, to obtain a second audio stream with a second bitrate, the second bitrate being lower than the first bitrate.

2 . The method according to claim 1 , wherein analog audio stream meeting the first target condition comprises:

the bitrate of the analog audio stream is less than or equal to the target transcoding bitrate; or

an audio stream quality parameter of the analog audio stream is greater than or equal to a quality parameter threshold.

3 . The method according to claim 1 , wherein at least one of the time-domain audio signal and the first signal, the target transcoding bitrate and the bitrate of the analog audio stream, or the number of completed iterations meets the second target condition comprises:

a similarity between the time-domain audio signal and the first signal is greater than or equal to a similarity threshold;

a difference between the target transcoding bitrate and the bitrate of the analog audio stream is less than or equal to a difference threshold; and

the number of completed iterations is equal to a threshold number.

4 . The method according to claim 1 , further comprising:

using a second candidate quantization parameter determined based on the target transcoding bitrate as an input of a next iteration process in response to the analog audio stream not meeting the first target condition, or the time-domain audio signal and the first signal, the target transcoding bitrate and the bitrate of the analog audio stream, and the number of completed iterations not meeting the second target condition.

5 . The method according to claim 1 , wherein performing entropy decoding on the first audio stream with the first bitrate, to obtain the audio feature parameter and the excitation signal of the first audio stream comprises:

obtaining appearance probabilities of a plurality of coding units in the first audio stream;

decoding the first audio stream based on the appearance probabilities, to obtain a plurality of decoding units respectively corresponding to the plurality of coding units; and

combining the plurality of decoding units, to obtain the audio feature parameter and the excitation signal of the first audio stream.

6 . The method according to claim 1 , wherein performing entropy coding on the target audio feature parameter and the target excitation signal, to obtain the second audio stream with the second bitrate comprises:

obtaining appearance probabilities of a plurality of coding units in the target audio feature parameter and the target excitation signal; and

coding the plurality of coding units based on the appearance probabilities, to obtain the second audio stream.

7 . The method according to claim 1 , further comprising:

performing forward error correction coding on a subsequently received audio stream based on the second audio stream.

8 . An audio transcoder, comprising a memory for storing instructions and a processor for executing the instructions to:

perform entropy decoding on a first audio stream with a first bitrate, to obtain an audio feature parameter and an excitation signal of the first audio stream without a complete parameter extraction process, the excitation signal being a quantized audio signal;

obtain a time-domain audio signal corresponding to the excitation signal based on the audio feature parameter and the excitation signal;

determine a first candidate quantization parameter based on a target transcoding bitrate through at least one iteration process;

simulate a re-quantization process of the excitation signal and the audio feature parameter based on the first candidate quantization parameter to obtain a first signal corresponding to the excitation signal and a first parameter corresponding to the audio feature parameter, wherein the processor is configured to simulate the re-quantization process by:

respectively simulating a discrete cosine transform process of the excitation signal and a discrete cosine transform process of the audio feature parameter, to obtain a second signal corresponding to the excitation signal and a second parameter corresponding to the audio feature parameter; and

performing rounding after the second signal and the second parameter are respectively divided by the first candidate quantization parameter;

simulate an entropy coding process of the first signal and the first parameter, to obtain an analog audio stream;

identify the first candidate quantization parameter as a first quantization parameter only in response to the analog audio stream meeting a first target condition and at least one of the time-domain audio signal and a first signal as an intermediate output of the simulation process, the target transcoding bitrate and a bitrate of the analog audio stream, or a number of completed iterations meeting a second target condition, the first quantization parameter being used for adjusting the first bitrate of the first audio stream to the target transcoding bitrate;

re-quantize the excitation signal and the audio feature parameter based on the time-domain audio signal and the first quantization parameter, to obtain a target excitation signal and a target audio feature parameter; and

perform entropy coding only on the target audio feature parameter and the target excitation signal, to obtain a second audio stream with a second bitrate, the second bitrate being lower than the first bitrate.

9 . The audio transcoder of claim 8 , wherein the analog audio stream meeting the first target condition comprises:

the bitrate of the analog audio stream is less than or equal to the target transcoding bitrate; or

an audio stream quality parameter of the analog audio stream is greater than or equal to a quality parameter threshold.

10 . The audio transcoder of claim 8 , wherein at least one of the time-domain audio signal and the first signal, the target transcoding bitrate and the bitrate of the analog audio stream, or the number of completed iterations meets the second target condition comprises:

a similarity between the time-domain audio signal and the first signal is greater than or equal to a similarity threshold;

a difference between the target transcoding bitrate and the bitrate of the analog audio stream is less than or equal to a difference threshold; and

the number of completed iterations is equal to a threshold number.

11 . The audio transcoder of claim 8 , wherein the processor is further configured to execute the instructions to:

use a second candidate quantization parameter determined based on the target transcoding bitrate as an input of a next iteration process in response to the analog audio stream not meeting the first target condition, or the time-domain audio signal and the first signal, the target transcoding bitrate and the bitrate of the analog audio stream, and the number of completed iterations not meeting the second target condition.

12 . The audio transcoder of claim 8 , wherein to perform entropy decoding on the first audio stream with the first bitrate, to obtain the audio feature parameter and the excitation signal of the first audio stream comprises:

obtaining appearance probabilities of a plurality of coding units in the first audio stream;

decoding the first audio stream based on the appearance probabilities, to obtain a plurality of decoding units respectively corresponding to the plurality of coding units; and

combining the plurality of decoding units, to obtain the audio feature parameter and the excitation signal of the first audio stream.

13 . The audio transcoder of claim 8 , wherein to perform entropy coding on the target audio feature parameter and the target excitation signal, to obtain the second audio stream with the second bitrate comprises:

obtaining appearance probabilities of a plurality of coding units in the target audio feature parameter and the target excitation signal; and

coding the plurality of coding units based on the appearance probabilities, to obtain the second audio stream.

14 . A non-transitory computer readable medium for storing computer instructions, the computer instructions when executed by an audio transcoding apparatus, cause the audio transcoding apparatus to:

perform entropy decoding on a first audio stream with a first bitrate, to obtain an audio feature parameter and an excitation signal of the first audio stream without a complete parameter extraction, the excitation signal being a quantized audio signal;

obtain a time-domain audio signal corresponding to the excitation signal based on the audio feature parameter and the excitation signal;

determine a first candidate quantization parameter based on a target transcoding bitrate through at least one iteration process;

simulate a re-quantization process of the excitation signal and the audio feature parameter based on the first candidate quantization parameter to obtain a first signal corresponding to the excitation signal and a first parameter corresponding to the audio feature parameter, wherein the computer instructions, when executed by the audio transcoding apparatus, cause the computer device to simulate the re-quantization process by:

respectively simulating a discrete cosine transform process of the excitation signal and a discrete cosine transform process of the audio feature parameter, to obtain a second signal corresponding to the excitation signal and a second parameter corresponding to the audio feature parameter; and

performing rounding after the second signal and the second parameter are respectively divided by the first candidate quantization parameter;

simulate an entropy coding process of the first signal and the first parameter, to obtain an analog audio stream;

identify the first candidate quantization parameter as a first quantization parameter only in response to the analog audio stream meeting a first target condition and at least one of the time-domain audio signal and a first signal as an intermediate output of the simulation process, the target transcoding bitrate and a bitrate of the analog audio stream, or a number of completed iterations meeting a second target condition, the first quantization parameter being used for adjusting the first bitrate of the first audio stream to the target transcoding bitrate;

re-quantize the excitation signal and the audio feature parameter based on the time-domain audio signal and the first quantization parameter, to obtain a target excitation signal and a target audio feature parameter; and

perform entropy coding only on the target audio feature parameter and the target excitation signal, to obtain a second audio stream with a second bitrate, the second bitrate being lower than the first bitrate.