# US 11,443,754 B2 · Concept for switching of sampling rates at audio processing devices

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- Number: US 11,443,754 B2
- Document ID: US11443754B2
- Status: Granted
- Kind: B2
- Application number: 16/996,671
- Filed: 2020-08-18
- Published: 2020-12-03
- Granted: 2022-09-13
- Earliest claimed: 2014-08-18
- Assignees: Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V.
- Applicants: Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V.
- Inventors: Stefan Doehla; Guillaume Fuchs; Bernhard Grill; Markus Multrus; Grzegorz Pietrzyk; Emmanuel Ravelli; Markus Schnell
- Web page: https://patentgrep.com/patent/US11443754B2

## CPC

- G10L 19/24: Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding
- G10L 19/173: {Transcoding, i.e. converting between two coded representations avoiding cascaded coding-decoding}
- G10L 19/18: Vocoders using multiple modes
- G10L 19/20: using sound class specific coding, hybrid encoders or object based coding
- G10L 19/22: Mode decision, i.e. based on audio signal content versus external parameters
- G10L 19/04: using predictive techniques
- G10L 2019/0002: {Codebook adaptations}
- G10L: SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING

## Abstract

Audio decoder device for decoding a bitstream, the audio decoder device including: a predictive decoder for producing a decoded audio frame from the bitstream, wherein the predictive decoder includes a parameter decoder for producing one or more audio parameters for the decoded audio frame from the bitstream and wherein the predictive decoder includes a synthesis filter device for producing the decoded audio frame by synthesizing the one or more audio parameters for the decoded audio frame; a memory device including one or more memories, wherein each of the memories is configured to store a memory state for the decoded audio frame, wherein the memory state for the decoded audio frame of the one or more memories is used by the synthesis filter device for synthesizing the one or more audio parameters for the decoded audio frame; and a memory state resampling device configured to determine the memory state for synthesizing the one or more audio parameters for the decoded audio frame, which has a sampling rate, for one or more of the memories by resampling a preceding memory state for synthesizing one or more audio parameters for a preceding decoded audio frame, which has a preceding sampling rate being different from the sampling rate of the decoded audio frame, for one or more of the memories and to store the memory state for synthesizing of the one or more audio parameters for the decoded audio frame for one or more of the memories into the respective memory.

## Claims

### Claim 1

Audio decoder device for decoding a bitstream, the audio decoder device comprising:
a predictive decoder for producing a decoded audio frame from the bitstream, wherein the predictive decoder comprises a parameter decoder for producing one or more audio parameters for the decoded audio frame from the bitstream and wherein the predictive decoder comprises a synthesis filter device for producing the decoded audio frame by synthesizing the one or more audio parameters for the decoded audio frame;
a memory device comprising one or more memories, wherein each of the memories is configured to store a memory state for the decoded audio frame, wherein the memory state for the decoded audio frame of the one or more memories is used by the synthesis filter device for synthesizing the one or more audio parameters for the decoded audio frame; and
a memory state resampling device configured to determine the memory state for the decoded audio frame, which comprises a sampling rate, for one or more of said memories by resampling a preceding memory state for synthesizing one or more audio parameters for a preceding decoded audio frame, which comprises a preceding sampling rate being different from the sampling rate of the decoded audio frame, for one or more of said memories and to store the memory state for the decoded audio frame for one or more of said memories into the one or more of said memories;
wherein the one or more memories comprise a synthesis filter memory configured to store a synthesis filter memory state for determining one or more synthesis filter parameters for the decoded audio frame, wherein the memory state resampling device is configured to determine the synthesis filter memory state for determining the one or more synthesis filter parameters for the decoded audio frame by resampling a preceding synthesis memory state for determining of one or more synthesis filter parameters for the preceding decoded audio frame and to store the synthesis memory state for determining of the one or more synthesis filter parameters for the decoded audio frame into the synthesis filter memory;
wherein a number of samples in the preceding synthesis memory state is calculated according to the formula MemSynRSizeOld=(int)(TI*fs1);
wherein a number of samples in the synthesis memory state is calculated according to the formula MemSynRSizeNew=(int)(TI*fs2);
wherein MemSynRSizeOld is the number of samples in the preceding synthesis memory state, wherein MemSynRSizeNew is the number of samples in the synthesis memory state, wherein fs1 is the preceding sampling rate, wherein fs2 is the sampling rate, wherein TI is a largest possible duration to be covered by the preceding syntheses filter memory state and by the syntheses filter memory state.

### Claim 2 (depends on 1)

Audio decoder device according to claim 1, wherein the one or more memories comprise an adaptive codebook memory configured to store an adaptive codebook memory state for determining one or more excitation parameters for the decoded audio frame, wherein the memory state resampling device is configured to determine the adaptive codebook memory state for determining the one or more excitation parameters for the decoded audio frame by resampling a preceding adaptive codebook memory state for determining of one or more excitation parameters for the preceding decoded audio frame and to store the adaptive codebook memory state for determining of the one or more excitation parameters for the decoded audio frame into the adaptive codebook memory.

### Claim 3 (depends on 1)

Audio decoder device according to claim 1, wherein the memory resampling device is configured in such way that the same synthesis filter parameters are used for a plurality of subframes of the decoded audio frame.

### Claim 4 (depends on 1)

Audio decoder device according to claim 1, wherein the memory resampling device is configured in such way that the resampling of the preceding synthesis filter memory state is done by transforming the preceding synthesis filter memory state for the preceding decoded audio frame to a power spectrum and by resampling the power spectrum.

### Claim 5 (depends on 1)

Audio decoder device according to claim 1, wherein the one or more memories comprise a de-emphasis memory configured to store a de-emphasis memory state for determining one or more de-emphasis parameters for the decoded audio frame, wherein the memory state resampling device is configured to determine the de-emphasis memory state for determining the one or more de-emphasis parameters for the decoded audio frame by resampling a preceding de-emphasis memory state for determining of one or more de-emphasis parameters for the preceding decoded audio frame and to store the de-emphasis memory state for determining of the one or more de-emphasis parameters for the decoded audio frame into the de-emphasis memory.

### Claim 6 (depends on 1)

Audio decoder device according to claim 1, wherein the one or more memories are configured in such way that a number of stored samples for the decoded audio frame is proportional to the sampling rate of the decoded audio frame.

### Claim 7 (depends on 1)

Audio decoder device according to claim 1, wherein the memory state resampling device is configured in such way that the resampling is done by linear interpolation.

### Claim 8 (depends on 1)

Audio decoder device according to claim 1, wherein the memory state resampling device is configured to retrieve the preceding memory state for one or more of said memories from the memory device.

### Claim 9 (depends on 1)

Audio decoder device according to claim 1, wherein the audio decoder device comprises an inverse-filtering device configured for inverse-filtering of the preceding decoded audio frame at the preceding sampling rate in order to determine the preceding memory state of one or more of said memories, wherein the memory state resampling device is configured to retrieve the preceding memory state for one or more of said memories from the inverse-filtering device.

### Claim 10 (depends on 1)

Audio decoder device according to claim 1, wherein the memory state resampling device is configured to retrieve the preceding memory state for one or more of said memories from a further audio processing device.

### Claim 11

Method for operating an audio decoder device for decoding a bitstream, the method comprising:
producing a decoded audio frame from the bitstream using a predictive decoder, wherein the predictive decoder comprises a parameter decoder for producing one or more audio parameters for the decoded audio frame from the bitstream and wherein the predictive decoder comprises a synthesis filter device for producing the decoded audio frame by synthesizing the one or more audio parameters for the decoded audio frame;
providing a memory device comprising one or more memories, wherein each of the memories is configured to store a memory state for the decoded audio frame, wherein the memory state for the decoded audio frame of the one or more memories is used by the synthesis filter device for synthesizing the one or more audio parameters for the decoded audio frame;
determining the memory state for the decoded audio frame, which comprises a sampling rate, for one or more of said memories by resampling a preceding memory state for synthesizing one or more audio parameters for a preceding decoded audio frame, which comprises a preceding sampling rate being different from the sampling rate of the decoded audio frame, for one or more of said memories; and
storing the memory state for the decoded audio frame for one or more of said memories into the one or more of said memories;
storing a synthesis filter memory state for determining one or more synthesis filter parameters for the decoded audio frame into a synthesis filter memory of the one or more memories;
determining, by using a memory state resampling device, the synthesis filter memory state for determining the one or more synthesis filter parameters for the decoded audio frame by resampling a preceding synthesis memory state for determining of one or more synthesis filter parameters for the preceding decoded audio frame;
storing, by using the memory state resampling device, the synthesis memory state for determining of the one or more synthesis filter parameters for the decoded audio frame into the synthesis filter memory;
wherein a number of samples in the preceding synthesis memory state is calculated according to the formula MemSynRSizeOld=(int)(TI*fs1);
wherein a number of samples in the synthesis memory state is calculated according to the formula MemSynRSizeNew=(int)(TI*fs2);
wherein MemSynRSizeOld is the number of samples in the preceding synthesis memory state, wherein MemSynRSizeNew is the number of samples in the synthesis memory state, wherein fs1 is the preceding sampling rate, wherein fs2 is the sampling rate, wherein TI is a largest possible duration to be covered by the preceding syntheses filter memory state and by the syntheses filter memory state.

### Claim 12

A non-transitory digital storage medium having a computer program stored thereon to perform the method for operating an audio decoder device for decoding a bitstream, the method comprising:
producing a decoded audio frame from the bitstream using a predictive decoder, wherein the predictive decoder comprises a parameter decoder for producing one or more audio parameters for the decoded audio frame from the bitstream and wherein the predictive decoder comprises a synthesis filter device for producing the decoded audio frame by synthesizing the one or more audio parameters for the decoded audio frame;
providing a memory device comprising one or more memories, wherein each of the memories is configured to store a memory state for the decoded audio frame, wherein the memory state for the decoded audio frame of the one or more memories is used by the synthesis filter device for synthesizing the one or more audio parameters for the decoded audio frame;
determining the memory state for the decoded audio frame, which comprises a sampling rate, for one or more of said memories by resampling a preceding memory state for synthesizing one or more audio parameters for a preceding decoded audio frame, which comprises a preceding sampling rate being different from the sampling rate of the decoded audio frame, for one or more of said memories; and
storing the memory state for the decoded audio frame for one or more of said memories into the one or more of said memories;
storing a synthesis filter memory state for determining one or more synthesis filter parameters for the decoded audio frame into a synthesis filter memory of the one or more memories;
determining, by using a memory state resampling device, the synthesis filter memory state for determining the one or more synthesis filter parameters for the decoded audio frame by resampling a preceding synthesis memory state for determining of one or more synthesis filter parameters for the preceding decoded audio frame;
storing, by using the memory state resampling device, the synthesis memory state for determining of the one or more synthesis filter parameters for the decoded audio frame into the synthesis filter memory;
wherein a number of samples in the preceding synthesis memory state is calculated according to the formula MemSynRSizeOld=(int)(TI*fs1);
wherein a number of samples in the synthesis memory state is calculated according to the formula MemSynRSizeNew=(int)(TI*fs2);
wherein MemSynRSizeOld is the number of samples in the preceding synthesis memory state, wherein MemSynRSizeNew is the number of samples in the synthesis memory state, wherein fs1 is the preceding sampling rate, wherein fs2 is the sampling rate, wherein TI is a largest possible duration to be covered by the preceding syntheses filter memory state and by the syntheses filter memory state,
when said computer program is run by a computer.

### Claim 13

Audio encoder device for encoding a framed audio signal, the audio encoder device comprising:
a predictive encoder for producing an encoded audio frame from the framed audio signal, wherein the predictive encoder comprises a parameter analyzer for producing one or more audio parameters for the encoded audio frame from the framed audio signal and wherein the predictive encoder comprises a synthesis filter device for producing a decoded audio frame by synthesizing one or more audio parameters for the decoded audio frame, wherein the one or more audio parameters for the decoded audio frame are the one or more audio parameters for the encoded audio frame;
a memory device comprising one or more memories, wherein each of the memories is configured to store a memory state for the decoded audio frame, wherein the memory state for the decoded audio frame of the one or more memories is used by the synthesis filter device for synthesizing the one or more audio parameters for the decoded audio frame; and
a memory state resampling device configured to determine the memory state for the decoded audio frame, which comprises a sampling rate, for one or more of said memories by resampling a preceding memory state for synthesizing one or more audio parameters for a preceding decoded audio frame, which comprises a preceding sampling rate being different from the sampling rate of the decoded audio frame, for one or more of said memories and to store the memory state for the decoded audio frame for one or more of said memories into the one or more of said memories;
wherein the one or more memories comprise a synthesis filter memory configured to store a synthesis filter memory state for determining one or more synthesis filter parameters for the decoded audio frame, wherein the memory state resampling device is configured to determine the synthesis filter memory state for determining the one or more synthesis filter parameters for the decoded audio frame by resampling a preceding synthesis memory state for determining of one or more synthesis filter parameters for the preceding decoded audio frame and to store the synthesis memory state for determining of the one or more synthesis filter parameters for the decoded audio frame into the synthesis filter memory;
wherein a number of samples in the preceding synthesis memory state is calculated according to the formula MemSynRSizeOld=(int)(TI*fs1);
wherein a number of samples in the synthesis memory state is calculated according to the formula MemSynRSizeNew=(int)(TI*fs2);
wherein MemSynRSizeOld is the number of samples in the preceding synthesis memory state, wherein MemSynRSizeNew is the number of samples in the synthesis memory state, wherein fs1 is the preceding sampling rate, wherein fs2 is the sampling rate, wherein TI is a largest possible duration to be covered by the preceding syntheses filter memory state and by the syntheses filter memory state.

### Claim 14 (depends on 13)

Audio encoder device according to claim 13, wherein the one or more memories comprise an adaptive codebook memory configured to store an adaptive codebook state for determining one or more excitation parameters for the decoded audio frame, wherein the memory state resampling device is configured to determine the adaptive codebook state for determining the one or more excitation parameters for the decoded audio frame by resampling a preceding adaptive codebook memory state for determining of one or more excitation parameters for the preceding decoded audio frame and to store the adaptive codebook memory state for determining of the one or more excitation parameters for the decoded audio frame into the adaptive codebook memory.

### Claim 15 (depends on 13)

Audio encoder device according to claim 13, wherein the memory state resampling device is configured in such way that the same synthesis filter parameters are used for a plurality of subframes of the decoded audio frame.

### Claim 16 (depends on 13)

Audio encoder device according to claim 13, wherein the memory resampling device is configured in such way that the resampling of the preceding synthesis filter memory state is done by transforming the preceding synthesis filter memory state for the preceding decoded audio frame to a power spectrum and by resampling the power spectrum.

### Claim 17 (depends on 13)

Audio encoder device according to claim 13, wherein the one or more memories comprise a de-emphasis memory configured to store a de-emphasis memory state for determining one or more de-emphasis parameters for the decoded audio frame, wherein the memory state resampling device is configured to determine the de-emphasis memory state for determining the one or more de-emphasis parameters for the decoded audio frame by resampling a preceding de-emphasis memory state for determining of one or more de-emphasis parameters for the preceding decoded audio frame and to store the de-emphasis memory state for determining of the one or more de-emphasis parameters for the decoded audio frame into the de-emphasis memory.

### Claim 18 (depends on 13)

Audio encoder device according to claim 13, wherein the one or more memories are configured in such way that a number of stored samples for the decoded audio frame is proportional to the sampling rate of the decoded audio frame.

### Claim 19 (depends on 13)

Audio encoder device according to claim 13, wherein the memory resampling device is configured in such way that the resampling is done by linear interpolation.

### Claim 20 (depends on 13)

Audio encoder device according to claim 13, wherein the memory state resampling device is configured to retrieve the preceding memory state for one or more of said memories from the memory device.

### Claim 21 (depends on 13)

Audio encoder device according to claim 13, wherein the audio encoder device comprises an inverse-filtering device configured for inverse-filtering of the preceding decoded audio frame in order to determine the preceding memory state for one or more of said memories, wherein the memory state resampling device is configured to retrieve the preceding memory state for one or more of said memories from the inverse-filtering device.

### Claim 22 (depends on 13)

Audio encoder device according to claim 13, wherein the memory state resampling device is configured to retrieve the preceding memory state for one or more of said memories from of a further audio processing device.

### Claim 23

Method for operating an audio encoder device for encoding a framed audio signal, the method comprising:
producing an encoded audio frame from the framed audio signal using a predictive encoder, wherein the predictive encoder comprises a parameter analyzer for producing one or more audio parameters for the encoded audio frame from the framed audio signal and wherein the predictive encoder comprises a synthesis filter device for producing a decoded audio frame by synthesizing one or more audio parameters for the decoded audio frame, wherein the one or more audio parameters for the decoded audio frame are the one or more audio parameters for the encoded audio frame;
providing a memory device comprising one or more memories, wherein each of the memories is configured to store a memory state for the decoded audio frame, wherein the memory state for the decoded audio frame of the one or more memories is used by the synthesis filter device for synthesizing the one or more audio parameters for the decoded audio frame;
determining the memory state for the decoded audio frame, which comprises a sampling rate, for one or more of said memories by resampling a preceding memory state for synthesizing one or more audio parameters for a preceding decoded audio frame, which comprises a preceding sampling rate being different from the sampling rate of the decoded audio frame, for one or more of said memories; and
storing the memory state for the decoded audio frame for one or more of said memories into the one or more of said memories;
storing a synthesis filter memory state for determining one or more synthesis filter parameters for the decoded audio frame into a synthesis filter memory of the one or more memories;
determining, by using a memory state resampling device, the synthesis filter memory state for determining the one or more synthesis filter parameters for the decoded audio frame by resampling a preceding synthesis memory state for determining of one or more synthesis filter parameters for the preceding decoded audio frame;
storing, by using the memory state resampling device, the synthesis memory state for determining of the one or more synthesis filter parameters for the decoded audio frame into the synthesis filter memory;
wherein a number of samples in the preceding synthesis memory state is calculated according to the formula MemSynRSizeOld=(int)(TI*fs1);
wherein a number of samples in the synthesis memory state is calculated according to the formula MemSynRSizeNew=(int)(TI*fs2);
wherein MemSynRSizeOld is the number of samples in the preceding synthesis memory state, wherein MemSynRSizeNew is the number of samples in the synthesis memory state, wherein fs1 is the preceding sampling rate, wherein fs2 is the sampling rate, wherein TI is a largest possible duration to be covered by the preceding syntheses filter memory state and by the syntheses filter memory state.

### Claim 24

A non-transitory digital storage medium having a computer program stored thereon to perform the method for operating an audio encoder device for encoding a framed audio signal, the method comprising:
producing an encoded audio frame from the framed audio signal using a predictive encoder, wherein the predictive encoder comprises a parameter analyzer for producing one or more audio parameters for the encoded audio frame from the framed audio signal and wherein the predictive encoder comprises a synthesis filter device for producing a decoded audio frame by synthesizing one or more audio parameters for the decoded audio frame, wherein the one or more audio parameters for the decoded audio frame are the one or more audio parameters for the encoded audio frame;
providing a memory device comprising one or more memories, wherein each of the memories is configured to store a memory state for the decoded audio frame, wherein the memory state for the decoded audio frame of the one or more memories is used by the synthesis filter device for synthesizing the one or more audio parameters for the decoded audio frame;
determining the memory state for the decoded audio frame, which comprises a sampling rate, for one or more of said memories by resampling a preceding memory state for synthesizing one or more audio parameters for a preceding decoded audio frame, which comprises a preceding sampling rate being different from the sampling rate of the decoded audio frame, for one or more of said memories; and
storing the memory state for the decoded audio frame for one or more of said memories into the one or more of said memories;
storing a synthesis filter memory state for determining one or more synthesis filter parameters for the decoded audio frame into a synthesis filter memory of the one or more memories;
determining, by using a memory state resampling device, the synthesis filter memory state for determining the one or more synthesis filter parameters for the decoded audio frame by resampling a preceding synthesis memory state for determining of one or more synthesis filter parameters for the preceding decoded audio frame;
storing, by using the memory state resampling device, the synthesis memory state for determining of the one or more synthesis filter parameters for the decoded audio frame into the synthesis filter memory;
wherein a number of samples in the preceding synthesis memory state is calculated according to the formula MemSynRSizeOld=(int)(TI*fs1);
wherein a number of samples in the synthesis memory state is calculated according to the formula MemSynRSizeNew=(int)(TI*fs2);
wherein MemSynRSizeOld is the number of samples in the preceding synthesis memory state, wherein MemSynRSizeNew is the number of samples in the synthesis memory state, wherein fs1 is the preceding sampling rate, wherein fs2 is the sampling rate, wherein TI is a largest possible duration to be covered by the preceding syntheses filter memory state and by the syntheses filter memory state,
when said computer program is run by a computer.