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

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.

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.