Rendering an audio-visual stream synchronized by a software clock in a personal computer

Claim 3

The method of claim 1 wherein the microprocessor clock is a counter and the software clock is a counter, and wherein the method further includes: reading the microprocessor clock running at the first frequency; determining when to increase the value of the software clock so that the software clock continues running at the second frequency; and when it is determined to increase the value of the software clock, increasing the value of the software clock so that the software clock continues to run at the second frequency.

Claim 4

The method of claim 1 wherein the portion of the audio-visual stream contains video data, wherein the step of receiving a portion includes receiving the portion wherein the portion is encoded using an MPEG compression standard, and wherein the step of rendering includes: decoding the portion of the audio-visual stream; and displaying the portion on a video display.

Claim 5

The method of claim 1 wherein the portion of the audio-visual stream contains audio data, wherein the step of receiving a portion includes receiving the portion wherein the portion is encoded using an AC3 compression standard, and wherein the step of rendering includes: decoding the portion of the audio-visual stream; and playing the portion on a speaker.

Claim 6

The method of claim 1 wherein the step of receiving a portion includes receiving the portion from a DVD CD-ROM.

Claim 9

The method of claim 6 wherein the software counter is periodically updated, the method further including: reading the hardware clock to determine a current time; determining a time difference between the current time and a last time that the software counter has been updated; scaling the time difference to the second frequency to determine whether the software counter should be updated to continue running at the second frequency; and when it is determined that the software counter should be updated, increasing the software counter by the scaled time difference such that the software counter continues to run at the second frequency.

Claim 10

An audio-visual rendering device comprising: a processor having a built-in clock running at a first frequency; a DVD drive for generating an audio-visual stream synchronized to a second frequency; a video display for displaying a video portion of the audio-visual stream; a speaker for playing an audio portion of the audio-visual stream; and a memory containing: a software clock running at the second frequency, the software clock generated from the built-in clock; and a program that reads the audio-visual stream from a memory location, the memory location neriodically updated with data from the DVD drive, that examines the software clock to determine whether it is time to render a part of the audio-visual stream, and that renders the part of the audio-visual stream when it is determined that it is time to render the part of the audio-visual stream.

Claim 11

An audio-visual rendering device comprising: a processor having a built-in clock running at a first frequency; a DVD drive for generating an audio-visual stream synchronized to a second frequency; a video display for displaying a video portion of the audio-visual stream; a speaker for playing an audio portion of the audio-visual stream; and a memory containing: a software clock running at the second frequency, the software clock generated from the built-in clock; and a program that reads the audio-visual stream from a memory location, the memory location neriodically updated with data from the DVD drive, that examines the software clock to determine whether it is time to render a part of the audio-visual stream, and that renders the part of the audio-visual stream when it is determined that it is time to render the part of the audio-visual stream.

Claim 12

The audio-visual rendering device of claim 8 wherein the part of the audio-visual stream has a time stamp and wherein the program determines when it is time to render the part by comparing the time stamp to a value of the software clock.

Claim 13

The audio-visual rendering device of claim 8 wherein the audio-visual rendering device is a personal computer.

Claim 14

The audio-visual rendering device of claim 8 wherein the audio portion of the audio-visual stream is encoded in accordance with an MPEG compression standard.

Claim 15

The audio-visual rendering device of claim 8 wherein the software clock executes on an asynchronous thread of the program.

Claim 16

The audio-visual rendering device of claim 8 wherein the video portion of the audio-visual stream is encoded in accordance with an MPEG compression standard.

Claim 17

The audio-visual rendering device of claim 13 wherein the audio-visual rendering device includes a decoder for decoding the video portion before being displayed on the video display.

Claim 18

The audio-visual rendering device of claim 8 wherein the audio portion of the audio-visual stream is encoded in accordance with an AC3 compression standard.

Claim 19

The audio-visual rendering device of claim 15 wherein the audio-visual rendering device includes a decoder for decoding the audio portion before being played by the speaker.

Claim 20

A computer-readable medium containing instructions for controlling an audio-visual rendering device having a hardware clock with a first frequency, the audio-visual rendering device for rendering an audio-visual stream synchronized to a second frequency, by performing the steps of: providing a software clock that runs at the second frequency, wherein the second frequency is different from the first frequency; receiving a portion of the audio-visual stream having an associated play time; determining when to render the portion of the audio-visual stream by comparing a value of the software clock to the associated play time; and when it is determined to render the portion of the audio-visual stream, rendering the portion of the audio-visual stream.

Claim 21

A computer-readable medium containing instructions for controlling an audio-visual rendering device having a hardware clock with a first frequency, the audio-visual rendering device for rendering an audio-visual stream synchronized to a second frequency, by performing the steps of: providing a software clock that runs at the second frequency, wherein the second frequency is different from the first frequency; receiving a portion of the audio-visual stream having an associated play time; determining when to render the portion of the audio-visual stream by comparing a value of the software clock to the associated play time; and when it is determined to render the portion of the audio-visual stream, rendering the portion of the audio-visual stream.

Claim 22

The computer-readable medium of claim 17 wherein the step of determining when to render includes: reading a current time from the hardware clock; and converting the current time to the second frequency.

Claim 23

The computer-readable medium of claim 17 wherein the hardware clock is a counter and the software clock is a counter, and further including: reading the hardware clock running at the first frequency; determining when to increase the value of the software clock so that the software clock continues running at the second frequency; and when it is determined to increase the value of the software clock, increasing the value of the software clock so that the software clock continues to run at the second frequency.

Claim 24

A computer-readable medium containing instructions for controlling a computer system to render an audio-visual stream, the computer system having a hardware clock running at a first frequency, by performing the steps of: reading an audio-visual stream in an encoded format from a DVD drive, the audio-visual stream having an audio portion with an audio play time and a video portion with a video play time, the audio portion and the video portion synchronized relative to a second frequency that is different than the first frequency; decoding the audio portion of the audio-visual stream; decoding the video portion of the audio-visual stream; executing a software counter that runs at the second frequency; determining whether it is time to render the decoded audio portion by comparing the audio play time to a value of the software counter; when it is determined that it is time to render the decoded audio portion, rendering the decoded audio portion; determining whether it is time to render the decoded video portion by comparing the video play time to the value of the software counter; and when it is determined that it is time to render the decoded video portion, rendering the decoded video portion.

Claim 25

A computer-readable medium containing instructions for controlling a computer system to render an audio-visual stream, the computer system having a hardware clock running at a first frequency, by performing the steps of: reading an audio-visual stream in an encoded format from a DVD drive, the audio-visual stream having an audio portion with an audio play time and a video portion with a video play time, the audio portion and the video portion synchronized relative to a second frequency that is different than the first frequency; decoding the audio portion of the audio-visual stream; decoding the video portion of the audio-visual stream; executing a software counter that runs at the second frequency; determining whether it is time to render the decoded audio portion by comparing the audio play time to a value of the software counter; when it is determined that it is time to render the decoded audio portion, rendering the decoded audio portion; determining whether it is time to render the decoded video portion by comparing the video play time to the value of the software counter; and when it is determined that it is time to render the decoded video portion, rendering the decoded video portion.

Claim 26

The computer-readable medium of claim 20 wherein the software counter is periodically updated, and further including: reading the hardware clock to determine a current time; determining a time difference between the current time and a last time that the software counter has been updated; scaling the time difference to the second frequency to determine whether the software counter should be updated to continue running at the second frequency; and when it is determined that the software counter should be updated, increasing the software counter by the scaled time difference such that the software counter continues to run at the second frequency.