Converting a single-bit audio stream to a single-bit audio stream with a constant edge rate

Patent metadata

Field	Value
Publication number	US-10418044-B2
Application number	US-201715706160-A
Country	US
Kind code	B2
Filing date	Sep 15, 2017
Priority date	Jan 30, 2017
Publication date	Sep 17, 2019
Grant date	Sep 17, 2019

Abstract

A single-bit audio stream can be converted to a modified single-bit audio stream with a constant edge rate while maintaining a modulation index of the original audio stream using direct mapping. With direct mapping, a pre-filter bank may be combined with a multi-bit symbol mapper to select symbols for the modified audio stream with a constant edge rate per symbol and the same modulation index as the original audio stream. The output of the pre-filter bank may be an audio stream with no consecutive full-scale symbols. Using the output of the pre-filter bank, a multi-bit symbol mapper may use the symbol selector to output a symbol with a constant edge rate per symbol and the same modulation index as the original signal. The symbols may be converted to an analog signal for reproduction of audio content using a transducer.

First claim

What is claimed is:

1. A method, comprising:
receiving a single-bit audio stream; and
converting the received single-bit audio stream into a converted single-bit audio stream having equivalent audio content as the received single-bit audio stream with a constant edge rate and a modulation index that is equal to the modulation index of the received single-bit audio stream scaled by a desired volume level.

2. The method of claim 1 , wherein the step of converting comprises generating the converted single-bit audio stream without consecutive full-scale symbols.

3. The method of claim 1 , wherein the step of converting comprises generating equivalent audio content by using multiple representations of a particular quantization symbol, wherein the multiple representations are alternatively encoded in the converted single-bit audio stream.

4. The method of claim 1 , wherein the step of converting comprises modifying an input modulation index of the received single-bit audio stream.

5. The method of claim 1 , wherein the step of converting comprises selecting symbols for the converted single-bit audio stream based, at least in part, on a desired volume level.

6. The method of claim 1 , further comprising outputting the converted single-bit audio stream to a current-steering digital-to-analog converter (DAC) to reproduce the audio content using a transducer.

7. The method of claim 1 , wherein the step of converting is performed, in part, by a poly-phase filter bank scheme.

8. The method of claim 1 , wherein the step of converting is performed, in part, by a magnitude compensation filter.

9. An apparatus, comprising:
an audio controller configured to perform steps comprising:
receiving a single-bit audio stream; and
converting the received single-bit audio stream into a converted single-bit audio stream having equivalent audio content as the received single-bit audio stream with a constant edge rate and a selected modulation index that is equal to the modulation index of the received single-bit audio stream scaled by a desired volume level.

10. The apparatus of claim 9 , wherein the audio controller is configured to convert by generating the converted single-bit audio stream without consecutive full-scale symbols.

11. The apparatus of claim 9 , wherein the audio controller is configured to convert by generating equivalent audio content by using multiple representations of a particular quantization symbol, wherein the multiple representations are alternatively encoded in the converted single-bit audio stream.

12. The apparatus of claim 9 , wherein the audio controller is configured to convert by selecting symbols for the converted single-bit audio stream based, at least in part, on a desired volume level.

13. The apparatus of claim 9 , wherein the apparatus further comprises a current-steering digital-to-analog converter (DAC) to reproduce the audio content using a transducer based on the converted single-bit audio stream.

14. The apparatus of claim 9 , wherein the audio controller comprises a poly-phase filter bank, and wherein the audio controller is configured to convert by using the poly-phase filter bank.

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Kamkar Shafagh
• Hester Dylan
• Duewer Bruce

Classifications

• H03M5/14

  Code representation, e.g. transition, for a given bit cell depending on the information in one or more adjacent bit cells, e.g. delay modulation code, double density code · CPC title

• H03M5/08 Primary

  Code representation by pulse width · CPC title

• G10L19/167 Primary

  Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes · CPC title

• G10L19/00 Primary

  Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis (in musical instruments G10H) · CPC title

• G10L19/0212

  using orthogonal transformation · CPC title