Audio-visual scrubbing system

• US 6,687,664 B1
• Filed: 10/15/1999
• Issued: 02/03/2004
• Est. Priority Date: 10/15/1999
• Status: Expired due to Term

• Current Assignee: Creative Technology Ltd.
• Original Assignee: Creative Technology Ltd.
• Inventors: Laroche, Jean, Dolson, Mark, Sussman, Robert
• Primary Examiner(s): CHAWAN, VIJAY B
• Application Number:
  US09/419,128
• Time in Patent Office: 1,572 Days
• Field of Search: 704/200.1, 704/500-504, 704/207, 704/258, 704/201-206, 345/723, 707/500.1, 707/500, 700/94, 381/54
• US Class Current: 704/201
• CPC Class Codes: G10L 21/04 Time compression or expansion

Abstract

A method and apparatus for an audio scrubbing system for synchronizing audio to an asynchronous clock while preserving pitch utilizes a phase-vocoder to implement time-scaling without pitch-shifting.

Claims

1. An audio scrubber system for processing a media file comprising:

a graphical user interface displaying a representation of the media file and a control icon for selecting a portion of the media file;

a user input device for allowing the user to manipulate the control icon to selectively indicate playback of the media file in a forward direction and in a reverse direction; and

an audio processing system, responsive to manipulation of the control icon, for implementing a phase-vocoder to playback a portion of an audio stream contained in the media file in real-time, the audio processing system comprising;

a clock extraction circuit operable to receive a clock signal produced in response to manipulation of the control icon and to generate a current analysis time specifying the audio stream synchronized to the clock signal, the clock signal indicating playback of audio stream in the forward direction or in the reverse direction;

an audio store, coupled to the clock extraction circuit, for storing the audio stream in digital format and for providing a current block of the audio stream specified by the current analysis time;

a processor, coupled to the audio store to receive the current block, the processor operable to;

perform an FFT on the current block to generate a set of frequency bins;

perform an inverse FFT on the frequency bins to generate a current output block of an audio output stream;

set an input phase vocoder input hop size equal to the difference between the current analysis time and an immediately previous analysis time divided by a sampling rate;

adjust a phase of the current output block relative to a previous output block based on the input hop size; and

overlap the current output block with a previous output block separated by a fixed output hop size; and

an audio output unit that contains a Digital to Analog Converter (DAC) and a DAC sample clock for providing a constant DAC clock rate, the audio output unit being coupled to the processor to receive the current output block and to render the current output block at the DAC clock rate.

2. The system of claim 1 where:

said audio processing system is responsive to vertical motion of the control icon, for implementing phase-vocoder change of pitch of a portion of the media file selected by the control icon.

3. The system of claim 1 where:

said audio processing system is responsive to pausing the control icon for implementing phase-vocoder sustainment of playback of portion of the audio file selected by the control icon.

4. A method for scrubbing an audio file, said method comprising the steps of:

displaying a representation of the audio file and a control icon;

manipulating the control icon to produce a clock signal indicating forward or reverse playback of the media file at a desired playback rate;

accessing an audio input stream from a portion of the media file indicated by a current location of the control icon;

extracting a current analysis time from the clock signal;

accessing the audio input stream based on the current analysis time to obtain a current input block;

setting a phase vocoder input hop size equal to the difference between the current analysis time and an immediately previous analysis time;

performing an FFT on the current input block to generate a set of frequency bins;

performing an inverse FFT on said frequency bins to generate a current output block of an audio output stream; and

overlapping the current output block with a previous output block separated by a fixed output hop size.

5. The method of claim 4 further comprising the step of:

manipulating the control icon to indicate a selected change of pitch of a portion of the media file; and

utilizing a phase-vocoder to implement the selected pitch change independently of the playback rate of the audio file.

6. An audio scrubber system for processing a media file comprising:

a graphical user interface displaying a representation of the media file and a control icon for selecting a portion of the media file;

a user input device for allowing the user to control the playback rate of the media file starting at the portion of the media file selected by the control icon; and

an audio processing system, responsive to displacement and direction of displacement of the user input device, for implementing a phase-vocoder to playback the portion of the media file in real-time in a direction and rate indicated by an amount of displacement and direction of displacement of the user input device while preserving pitch, wherein a clock signal is produced indicative of the displacement and the direction of displacement,

the audio processing system configured to perform the steps of;

extracting a current analysis time from the clock signal;

accessing a current input block of an audio stream contained in the portion of the media file selected by the control icon, the current input block corresponding to the current analysis time;

setting a phase vocoder input hop size equal to the difference between the current analysis time and an immediately previous analysis time;

performing an FFT on the current input block to generate a set of frequency bins;

performing an inverse FFT on said frequency bins to generate a current output block of an audio output stream; and

overlapping the current output block with a previous output block separated by a fixed output hop size.

7. The system of claim 6 wherein:

said user input device is a jog-wheel that indicates a playback rate proportional to an amount of rotation from a start position.

8. A method for producing an audio output stream that is synchronized to an asynchronous clock, said method comprising the steps of:

presenting a graphical representation of an audio input stream;

presenting a graphical representation of a control icon;

detecting an indication of manipulations of the control icon and producing a variable rate asynchronous clock in response thereto;

extracting a current analysis time from the variable rate asynchronous clock;

accessing a current input block from the audio input stream for the purpose of generating an audio output stream, the current input block corresponding to the current analysis time;

setting a phase vocoder input hop size equal to the difference between the current analysis time and an immediately previous analysis time;

performing an FFT on the current input block to generate a set of frequency bins;

performing an inverse FFT on the frequency bins to generate a current output block of the audio output stream; and

overlapping the current output block with a previous output block separated by a fixed output hop size.

9. The system of claim 8 wherein the control icon is a cursor, the method further including detecting input from an input device, the manipulation of the control icon being based on the input from the input device.

10. The system of claim 8 wherein the control icon is representative of a jog-wheel.