Digital audio signal filtering mechanism and method

• US 20050065780A1
• Filed: 10/29/2004
• Published: 03/24/2005
• Est. Priority Date: 11/07/1997
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Brownell, Jason, Wiser, Philip R., Heringer, Leeann, Rishniw, Leon, Kearby, Gerry
• Granted Patent: US 7,206,650 B2
• Time in Patent Office: Days
• US Class Current: 704/201
• 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

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

storing in a memory of a computer, processing parameter data related to the two or more transmission 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 to one or more of the transmission medium characteristics of the transmission mediums to produce the encoded audio signal for subsequent transmission through one of the two or more transmission mediums selected for the transmission of the encoded audio signal;

receiving signals which specify the transmission medium selected for the transmission of the encoded audio signal;

retrieving from the memory, the processing parameter data related to the transmission medium selected for the transmission of the encoded audio signal; 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 transmission through the transmission medium selected for the transmission of the encoded audio signal.

47. The method of claim 46 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 transmission mediums include delivery sample rate data which specify a transmission sample rate of the encoded audio signal;

(ii) further wherein the processing in the two or more cascaded processing stages further comprises re-sampling the audio signal in accordance with the sample rate data to produce a decimated/interpolated intermediate signal which has the transmission sample rate; and

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

48. The method of claim 47 wherein the filtering parameter data include equalization data specifying one or more filters, each of which is selected from a group consisting of low shelf, band pass, and high shelf filters.

49. The method of claim 47 wherein the filtering parameter data include data specifying one or more filters, each of which is selected from a group consisting of expander, compressor, and limiter filters.

50. The method of claim 46 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 transmission mediums include transmission channel type data which specify a transmission channel type which is selected from the group consisting of a stereo channel type and mono-aural channel type;

(ii) further wherein the processing in the two or more cascaded processing stages further comprises converting the audio signal to the delivery channel type in accordance with the transmission channel type data to produce a format converted intermediate signal which has the transmission channel type; and

(iii) further wherein the two or more cascaded processing stages further comprises a step of filtering comprising filtering the format converted intermediate signal in the filtering step in accordance with a filtering parameter data of the retrieved processing parameter data to produce a filtered audio signal.

51. The method of claim 50 wherein the filtering parameter data include equalization data specifying one or more filters, each of which is selected from a group consisting of low shelf, band pass, and high shelf filters.

52. The method of claim 50 wherein the filtering parameter data include data specifying one or more filters, each of which is selected from a group consisting of expander, compressor, and limiter filters.

53. 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 transmission through one of two or more transmission mediums selected for the transmission of the encoded audio signal, each of which has one or more transmission medium characteristics, by performing the steps of:

storing in a memory of a computer, processing parameter data related to the two or more transmission 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 to one or more of the transmission medium characteristics of the transmission mediums to produce the encoded audio signal for subsequent transmission through one of the two or more transmission mediums selected for the transmission of the encoded audio signal;

receiving signals which specify the transmission medium selected for the transmission of the encoded audio signal;

retrieving from the memory, the processing parameter data related to the transmission medium selected for the transmission of the encoded audio signal; 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 transmission through the transmission medium selected for the transmission of the encoded audio signal.

54. The computer readable medium of claim 53 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 transmission mediums include delivery sample rate data which specify a transmission sample rate of the encoded audio signal;

(ii) further wherein the processing in the two or more cascaded processing stages further comprises re-sampling the audio signal in accordance with the sample rate data to produce a decimated/interpolated intermediate signal which has the transmission sample rate; and

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

55. The computer readable medium of claim 54 wherein the filtering parameter data include equalization data specifying one or more filters, each of which is selected from a group consisting of low shelf, band pass, and high shelf filters.

56. The computer readable medium of claim 54 wherein the filtering parameter data include data specifying one or more filters, each of which is selected from a group consisting of expander, compressor, and limiter filters.

57. The computer readable medium of claim 53 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 transmission mediums include transmission channel type data which specify a transmission channel type which is selected from the group consisting of a stereo channel type and mono-aural channel type;

(ii) further wherein the processing in the two or more cascaded processing stages further comprises converting the audio signal to the delivery channel type in accordance with the transmission channel type data to produce a format converted intermediate signal which has the transmission channel type; and

(iii) further wherein the two or more cascaded processing stages further comprises a step of filtering comprising filtering the format converted intermediate signal in the filtering step in accordance with a filtering parameter data of the retrieved processing parameter data to produce a filtered audio signal.

58. The computer readable medium of claim 57 wherein the filtering parameter data include equalization data specifying one or more filters, each of which is selected from a group consisting of low shelf, band pass, and high shelf filters.

59. The computer readable medium of claim 57 wherein the filtering parameter data include data specifying one or more filters, each of which is selected from a group consisting of expander, compressor, and limiter filters.

60. 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 transmission through one of two or more transmission mediums selected for the transmission of the encoded audio signal, each of which has one or more transmission medium characteristics, by performing the steps of;

storing in a memory of a computer, processing parameter data related to the two or more transmission 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 to one or more of the transmission medium characteristics of the transmission mediums to produce the encoded audio signal for subsequent transmission through one of the two or more transmission mediums;

receiving signals which specify the transmission medium selected for the transmission of the encoded audio signal;

retrieving from the memory, the processing parameter data related to the transmission medium selected for the transmission of the encoded audio signal; 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 transmission through the transmission medium selected for the transmission of the encoded audio signal.

61. The computer system of claim 60 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 transmission mediums include delivery sample rate data which specify a transmission sample rate of the encoded audio signal;

(ii) further wherein the processing in the two or more cascaded processing stages further comprises re-sampling the audio signal in accordance with the sample rate data to produce a decimated/interpolated intermediate signal which has the transmission sample rate; and

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

62. The computer system of claim 61, wherein the filtering parameter data include equalization data specifying one or more filters, each of which is selected from a group consisting of low shelf, band pass, and high shelf filters.

63. The computer system of claim 61, wherein the filtering parameter data include data specifying one or more filters, each of which is selected from a group consisting of expander, compressor, and limiter filters.

64. The computer system of claim 61 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 transmission mediums include transmission channel type data which specify a transmission channel type which is selected from the group consisting of a stereo channel type and mono-aural channel type;

(ii) further wherein the processing in the two or more cascaded processing stages further comprises converting the audio signal to the delivery channel type in accordance with the transmission channel type data to produce a format converted intermediate signal which has the transmission channel type; and

(iii) further wherein the two or more cascaded processing stages further comprises a step of filtering comprising filtering the format converted intermediate signal in the filtering step in accordance with a filtering parameter data of the retrieved processing parameter data to produce a filtered audio signal.

65. The computer system of claim 64, wherein the filtering parameter data include equalization data specifying one or more filters, each of which is selected from a group consisting of low shelf, band pass, and high shelf filters.

66. The computer system of claim 64, wherein the filtering parameter data include data specifying one or more filters, each of which is selected from a group consisting of expander, compressor, and limiter filters.