Digital audio compensation

• US 6,763,274 B1
• Filed: 12/18/1998
• Issued: 07/13/2004
• Est. Priority Date: 12/18/1998
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Placeware, Inc. (Microsoft Corporation)
• Inventors: Gilbert, Erik J.
• Primary Examiner(s): Lee, Ping
• Application Number:
  US09/216,315
• Time in Patent Office: 2,034 Days
• Field of Search: 700/94, 370/503, 370/504, 370/509, 370/510, 370/513, 370/516, 370/517, 370/505
• US Class Current: 700/94
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm

Abstract

A method and apparatus for audio compensation is disclosed. If audio input components and audio output components are not driven by a common clock (e.g., input and output systems are separated by a network, different clock signals in a single computer system), input and output sampling rates may differ. Also, network routing of the digital audio data may not be consistent. Both clock synchronization and routing considerations can affect the digital audio output. To compensate for the timing irregularities caused by clock synchronization differences and/or routing changes, the present invention adjusts periods of silence in the digital audio data being output. The present invention thereby provides an improved digital audio output.

Claims

1. A method of audio compensation, the method comprising:

receiving a stream of audio packets, wherein the stream of audio packets comprises at least one period of silence;

determining a time difference between a first time stamp for a first audio packet from the stream of audio packets, and a second time stamp for a second audio packet from the stream of audio packets;

determining a playing time for the first audio packet;

determining a timing relationship based on a comparison of the time difference and the playing time;

determining whether the at least one period of silence is greater than a predetermined threshold value; and

adjusting the at least one period of silence within an audio segment based on the timing relationship between an audio input and an audio output if the period of silence is greater than the predetermined threshold value.

2. The method of claim 1 wherein adjusting the length of the at least one period of silence comprises removing audio samples from the period of silence if the timing relationship indicates that the audio output is slower than the audio input.

3. The method of claim 1 wherein adjusting the length of the at least one period of silence comprises replaying audio samples from the period of silence if the timing relationship indicates that the audio input is slower than the audio output.

4. The method of claim 1 wherein the period of silence is based on a time average strength of an audio packet.

5. The method of claim 1 wherein the audio input is generated by a first computer system and the audio output is played by a second computer system.

6. The method of claim 1 wherein the audio input is generated by and the audio output is played by a single computer system.

7. A machine-readable medium having stored thereon sequences of instructions that when execute by one or more processors cause the one or more processors to:

determine a time difference between a first time stamp for a first audio packet and a second audio time stamp for a second audio packet;

determine a playing time for the first audio packet;

determine a timing relationship based on a comparison of the time difference and the playing time;

determine whether a length of a period of silence is greater than a predetermined threshold value; and

adjust the length of a period of silence based on the timing relationship between an audio input and an audio output if the length of the period of silence is greater than the predetermined threshold value.

8. The machine-readable of medium of claim 7 wherein sequences of instructions that cause the one or more processors to adjust the length of a period of silence comprise sequences of instructions that, when executed, cause the one or more processors to determine the period of silence based on the average strength of an audio packet.

9. An apparatus for audio compensation, the apparatus comprising:

means for determining a time difference between a first time stamp for a first audio packet and a second time stamp for a second audio packet;

means for determining a playing time for the fist audio packet;

means for determining a timing relationship based on a comparison of the time difference and the playing time;

means for determining whether a length of a period of silence is greater than a predetermined threshold value and

means for adjusting the length of a period of silence based on the timing relationship between an audio input and an audio output if the length of the period of silence is greater than the predetermined threshold value.

10. The apparatus of claim 9 further comprising means for determining a period of silence based on a time average strength of an audio packet.

11. The apparatus of claim 9 wherein the audio input is generated by a first computer system and the audio output is played by a second computer system.

12. The apparatus of claim 9 wherein the audio input is generated by and the audio output is played by a single computer system.