Digital audio signal filtering mechanism and method

• US 6,959,220 B1
• Filed: 11/07/1997
• Issued: 10/25/2005
• Est. Priority Date: 11/07/1997
• Status: Expired due to Fees

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Herenger, Leeann, Kearby, Gerry, Rishniw, Leon, Browell, Jason, Wiser, Philip R.
• Primary Examiner(s): Tran, Sinh
• Assistant Examiner(s): Pendleton, Brian T.
• Application Number:
  US08/966,072
• Time in Patent Office: 2,909 Days
• Field of Search: 709/217, 709/219, 709/231, 709/232, 709/247, 381/98, 381/103, 381/17, 725 92- 95
• US Class Current: 700/94
• CPC Class Codes: G11B 20/10527 Audio or video recording; Data buffering arrangements G11B20/12 - G11B20/18 take precedence
• CPC Class Codes: G11B 2020/10546 specifically adapted for audio data
• CPC Class Codes: H04S 3/008 in which the audio signals are in digital form, i.e. employing more than two discrete digital channels data reduction aspects thereof based on psychoacoustics G10L19/02
• CPC Class Codes: H04S 7/307 Frequency adjustment, e.g. tone control H04S7/301 takes precedence
• CPC Class Codes: H04S 7/40 Visual indication of stereophonic sound image

Abstract

Essentially all of the processing parameters which control processing of a source audio signal to produce an encoded audio signal are stored in an audio processing profile. Multiple audio processing profiles are stored in a processing profile database such that specific combinations of processing parameters can be retrieved and used at a later time. Audio processing profiles are organized according to specific delivery bandwidths such that a sound engineer can quickly and efficiently encode audio signals for each of a number of distinct delivery media. Synchronized A/B switching during playback of various encoded audio signals allows the sound engineer to detect nuances in the sound characteristics of the various encoded audio signals.

Claims

1. A method for processing an audio signal to produce an encoded audio signal for subsequent delivery through a selected one of two or more delivery mediums, each of which has one or more medium characteristics, the method comprising:

storing in a memory of a computer processing parameter data for each of the two or more delivery mediums—

wherein the processing parameter data specifies audio signal processing in two or more cascaded processing stages by which the audio signal is processed according one or more of the medium characteristics of the delivery mediums to produce the encoded audio signal for subsequent delivery through a corresponding one of the two or more delivery mediums;

receiving signals which specify the selected delivery medium;

retrieving from the memory the processing parameter data for the selected delivery medium; and

processing the audio signal in the two or more cascaded processing stages in accordance with the retrieved processing parameter data to produce the encoded audio signal for subsequent delivery through the selected delivery medium, wherein the two or more cascaded processing stages include a filtering stage and an encoding stage;

(i) further wherein the processing parameter data for each of the two or more delivery mediums include;

filtering parameter data which specify audio signal filtering in the filtering stage by which a filtered audio signal is produced from the audio signal; and

encoding parameter data which specify audio signal encoding in the encoding stage by which the filtered audio signal is encoded to form the encoded audio signal;

(ii) further wherein the step of processing comprises;

filtering the audio signal in the filtering stage in accordance with the filtering parameter data of the retrieved processing parameter data to produce the filtered audio signal; and

encoding the filtered audio signal in the encoding stage in accordance with the encoding parameter data of the retrieved processing parameter data to produce the encoded audio signal for subsequent delivery through the selected delivery medium.

2. The method of claim 1 wherein the two or more cascaded processing stages further include a sample rate converter stage;

(i) further wherein the processing parameter data for each of the two or more delivery mediums include delivery sample rate data which specify a delivery sample rate of the encoded audio signal;

(ii) further wherein the step of processing further comprises re-sampling the audio signal in accordance with the sample rate data to produce a decimated/interpolated intermediate signal which has the delivery sample rate;

(iii) further wherein the step of filtering comprises filtering the decimated/interpolated intermediate signal in the filtering stage in accordance with the filtering parameter data of the retrieved processing parameter data to produce the filtered audio signal.

3. The method of claim 1 wherein the two or more cascaded processing stages further include a format converter stage;

(i) further wherein the processing parameter data for each of the two or more delivery mediums include delivery channel type data which specify a delivery channel type which is selected from the group consisting of a stereo channel type and mono-aural channel type;

(ii) further wherein the step of processing further comprises converting the audio signal to the delivery channel type in accordance with the channel type data to produce a format converted intermediate signal which has the delivery channel type;

(iii) further wherein the step of filtering comprises filtering the format converted intermediate signal in the filtering stage in accordance with the filtering parameter data of the retrieved processing parameter data to produce the filtered audio signal.

4. The method of claim 1 wherein the filtering parameter data include equalization data specifying one or more filters, each of which is selected from the group consisting of low shelf, band pass, and high shelf filters.

5. The method of claim 1 wherein the filtering parameter data include data specifying one or more filters, each of which is selected from the group consisting of expander, compressor, and limiter filters.

6. A computer readable medium useful in association with a computer which includes a processor and a memory, the computer readable medium including computer instructions which are configured to cause the computer to process an audio signal to produce an encoded audio signal for subsequent delivery through a selected one of two or more delivery mediums, each of which has one or more medium characteristics, by performing the steps of:

storing in a memory of a computer, processing parameter data for each of the two or more delivery mediums wherein the processing parameter data specifies audio signal processing in two or more cascaded processing stages by which the audio signal is processed according one or more of the medium characteristics of the delivery mediums to produce the encoded audio signal for subsequent delivery through a corresponding one of the two or more delivery mediums;

receiving signals which specify the selected delivery medium;

retrieving from the memory the processing parameter data for the selected delivery medium; and

processing the audio signal in the two or more cascaded processing stages in accordance with the retrieved processing parameter data to produce the encoded audio signal for subsequent delivery through the selected delivery medium, wherein the two or more cascaded processing stages include a filtering stage and an encoding stage;

(i) further wherein the processing parameter data for each of the two or more delivery mediums include;

filtering parameter data which specify audio signal filtering in the filtering stage by which a filtered audio signal is produced from the audio signal; and

encoding parameter data which specify audio signal encoding in the encoding stage by which the filtered audio signal is encoded to form the encoded audio signal;

(ii) further wherein the step of processing comprises;

filtering the audio signal in the filtering stage in accordance with the filtering parameter data of the retrieved processing parameter data to produce the filtered audio signal; and

encoding the filtered audio signal in the encoding stage in accordance with the encoding parameter data of the retrieved processing parameter data to produce the encoded audio signal for subsequent delivery through the selected delivery medium.

7. The computer readable medium of claim 6 wherein the two or cascaded processing stages further include a sample rate converter stage;

(i) further wherein the processing parameter data for each of the two or more delivery mediums include delivery sample rate data which specify a delivery sample rate of the encoded audio signal;

(ii) further wherein the step of processing further comprises re-sampling the audio signal in accordance with the sample rate data to produce a decimated/interpolated intermediate signal which has delivery sample rate;

(iii) further wherein the step of filtering comprises filtering the decimated/interpolated intermediate signal in the filtering stage in accordance with the filtering parameter data of the retrieved processing parameter data to produce the filtered audio signal.

8. The computer readable medium of claim 6 wherein the two or more cascaded processing stages further include a format converter stage;

(i) further wherein the processing parameter data for each of the two or more delivery mediums include delivery channel type data which specify a delivery channel type which is selected from the group consisting of a stereo channel type and mono-aural channel type;

(ii) further wherein the step of processing further comprises converting the audio signal to the delivery channel type in accordance with the channel type data to produce a format converted intermediate signal which has the delivery channel type;

(iii) further wherein the step of filtering comprises filtering the format converted intermediate signal in the filtering stage in accordance with the filtering parameter data of the retrieved processing parameter data to produce the filtered audio signal.

9. The computer readable medium of claim 6 wherein the filtering parameter data include equalization data specifying one or more filters, each of which is selected from the group consisting of low shelf, band pass, and high shelf filters.

10. The computer readable medium of claim 6 wherein the filtering parameter data include data specifying one or more filters, each of which is selected from the group consisting of expander, compressor, and limiter filters.

11. A computer system comprising:

a processor;

a memory operatively coupled to the processor; and

an audio signal processor which executes in the processor from the memory and which, when executed by the processor, causes the computer to process an audio signal to produce an encoded audio signal for subsequent delivery through a selected one of two or more delivery mediums, each of which has one or more medium characteristics, by performing the steps of;

storing in a memory of a computer, processing parameter data for each of the two or more delivery mediums wherein the processing parameter data specifies audio signal processing in two or more cascaded processing stages by which the audio signal is processed according one or more of the medium characteristics of the delivery mediums to produce the encoded audio signal for subsequent delivery through a corresponding one of the two or more delivery mediums;

receiving signals which specify the selected delivery medium;

retrieving from the memory the processing parameter data for the selected delivery medium; and

processing the audio signal in the two or more cascaded processing stages in accordance with the retrieved processing parameter data to produce the encoded audio signal for subsequent delivery through the selected delivery medium, wherein the two or more cascaded processing stages include a filtering stage and an encoding stage;

(i) further wherein the processing parameter data for each of the two or more delivery mediums include;

filtering parameter data which specify audio signal filtering in the filtering stage by which a filtered audio signal is produced from the audio signal; and

encoding parameter data which specify audio signal encoding in the encoding stage by which the filtered audio signal is encoded to form the encoded audio signal;

(ii) further wherein the step of processing comprises;

filtering the audio signal in the filtering stage in accordance with the filtering parameter adapt of the retrieved processing parameter data to produce the filtered audio signal; and

encoding the filtered audio signal in the encoding stage in accordance with the encoding parameter data of the retrieved processing parameter data to produce the encoded audio signal for subsequent delivery through the selected delivery medium.

12. The computer system of claim 11 wherein the two or more cascaded processing stages further include a sample rate converter stage;

(i) further wherein the processing parameter data for each of the two or more delivery mediums include delivery sample rate data which specify a delivery sample rate of the encoded audio signal;

(ii) further wherein the step of processing further comprises re-sampling the audio signal in accordance with the sample rate data to produce a decimated/interpolated intermediate signal which has delivery sample rate;

(iii) further wherein the step of filtering comprises filtering the decimated/interpolated intermediate signal in the filtering stage in accordance with the filtering parameter data of the retrieved processing parameter data to produce the filtered audio signal.

13. The computer system of claim 11 wherein the two or more cascaded processing stages further include a format converted stage;

(i) further wherein the processing parameter data for each of the two or more delivery mediums include delivery channel type data which specify a delivery channel type which is selected from the group consisting of a stereo channel type and mono-aural channel type;

(ii) further wherein the step of processing further comprises converting the audio signal to the delivery channel type in accordance with the channel type data to produce a format converted intermediate signal which has the delivery channel type;

(iii) further wherein the step of filtering comprises filtering the format converted intermediate signal in the filtering stage in accordance with the filtering parameter data of the retrieved processing parameter data to produce the filtered audio signal.

14. The computer system of claim 11 wherein the filtering parameter data include equalization data specifying one or more filters, each of which is selected from the group consisting of low shelf, band pass, and high shelf filters.

15. The computer system of claim 11 wherein the filtering parameter data include data specifying one or more filters, each of which is selected from the group consisting of expander, compressor, and limiter filters.