Television – Camera – system and detail – Camera image stabilization
Reexamination Certificate
1998-08-19
2003-07-08
Garber, Wendy R. (Department: 2612)
Television
Camera, system and detail
Camera image stabilization
C348S014130, C382S236000, C375S240020, C375S240160
Reexamination Certificate
active
06590607
ABSTRACT:
TECHNICAL FIELD
The invention relates generally to the storing of digital video streams and more particularly to the storing of uninterrupted digital video streams using a motion-sensitive memory system, such as an optical memory system.
BACKGROUND ART
Present electronic devices allow for the recording of video data in a digital format. A common format for recording digital video data is defined by the Motion Picture Expert Group (MPEG) and is known as the MPEG format. Because digital video data is extremely voluminous, the MPEG format allows captured digital video data to be compressed before it is stored. Digital video data is stored on a variety of media, including magnetic tapes, magnetic disks, and optical disks. In the optical storage field, digital video data is commonly stored on read only memory (ROM) disks, such as digital video disks (DVDs).
Current advances in the optical storage field include optical memory systems that allow writing and/or rewriting of data onto optical disks. In writing data to an optical disk, a write head directs a beam of laser light into narrow recording tracks on the optical disk. Unwanted motion of the write head during writing can cause the laser beam to improperly contact the desired recording track, thereby degrading the quality of the recorded data. Because of the motion sensitivity of optical writing systems, optical writing systems are typically employed only in stable devices, such as desktop computers.
As previously noted, video images captured in digital video format require a large volume of storage memory. Because of the large storage capacity of optical storage systems, it is desirable to optically record or write digital video data onto an optical disk. For example, a handheld video camera equipped with an optical memory system that writes data onto an optical disk provides the ability to capture a large volume of video data without having to repeatedly exchange the storage media.
One problem with writing digital video data to an optical disk incorporated into a handheld video camera is that optical memory systems are motion-sensitive and a handheld camera is susceptible to motion caused by the user or the environment of the user (i.e., recording digital video data while traveling in a moving car).
FIG. 1
is a depiction of the components of a handheld digital video camera system
10
that records digital video data onto an optical memory disk. The digital video capture device
12
is a conventional video camera that combines optical lenses and a charge coupled device (CCD) array to electronically capture image data in a digital format. Digital video data that is captured in the digital video capture device is forwarded to a compression unit
14
that compresses the digital video data using conventional compression techniques. The compressed digital video data is forwarded to a write buffer
16
that buffers the compressed digital video data in order to smooth out the delivery of the compressed video data to an optical memory system
18
.
The write buffer
16
is typically made up of a fixed amount of RAM memory that is incorporated into the video camera circuitry. The conventional optical memory system includes a write head and an optical disk spindle. The write head includes a laser source that is used to optically write digital video data to the narrow tracks of an optical disk that is located on the optical disk spindle. As stated above, the writing process is a very motion sensitive and precise operation. If mechanical disturbances beyond a certain threshold are encountered by an optical memory system during data writing, it is likely that the data writing will be adversely affected. For example, when data writing is continued during a mechanical disturbance, video data recorded on adjacent tracks of the disk may be destroyed or rendered unreadable. In order to minimize the problems involved with writing to an optical memory system, it is desirable to momentarily stop recording when unacceptable mechanical disturbances, measured as motion or acceleration, are detected by an acceleration detection device, such as an accelerometer
20
.
While momentarily stopping writing to an optical disk during periods of mechanical disturbances avoids recording inaccurate digital video data and/or destroying data on adjacent tracks, possibly rendering the disk unreadable, a different problem may be created if data writing is suspended for too long a period of time. The problem involves overflowing the write buffer
16
that is located between the compression unit
14
and the optical memory system
18
. Assuming a continuous stream of digital video data is being generated by the video capture device
12
during the time that writing to the optical memory system is suspended, the write buffer is accumulating the digital video data that cannot be written to the optical memory system. If the write buffer reaches its storage capacity, instead of having unreliable data recorded because of mechanical disturbances, complete portions of digital video data will be lost as the write buffer begins to drop data for which it has no storage capacity.
Prior art solutions to the problem of writing data in spite of mechanical disturbances include increasing the size of the write buffer
16
and/or increasing the write head tracking bandwidth of the optical memory system
18
. For example, the write buffer can be made sufficiently large such that digital video data captured during a mechanical disturbance is absorbed into the large write buffer until the optical memory system can resume recording. While increasing the capacity of the write buffer may work well, it may not be cost-effective to simply add RAM to the write buffer. Regarding increasing the write head tracking bandwidth of the optical memory system for the purpose of solving the writing problem, additional mechanical stabilization would likely have to be added to the memory system along with feed forward control of the write head actuator based on input from the accelerometer to stabilize the write head and the optical disk. Again, this adds to the expense of the video system and may not be cost-effective.
In view of the stated shortcomings of the techniques used to overcome the problems involved with storing digital video data with motion-sensitive memory systems, what is needed is a method and apparatus that can store uninterrupted streams of compressed digital video data even when mechanical disturbances cause data writing to be temporarily interrupted.
It is important to note that there is a large volume of prior art that deals with increasing the capture rate for recording video data that includes images in a first pace motion, such as a horse running in front of a fixed landscape, and that deals with minimizing the shake that is perceived in a video stream that is recorded with an unsteady camera. Although prior art concerning these two concerns may seem related to the present disclosure, this prior art is only concerned with how video data is captured and compressed, rather than how the video data is transferred to a long-term storage medium, such as an optical disk.
SUMMARY OF THE INVENTION
A method and apparatus for storing an uninterrupted digital video stream with a motion-sensitive memory system involve monitoring the acceleration experienced by the memory system and adjusting the compression of the digital video stream in response to the acceleration. In the preferred embodiment, a threshold-related condition is established such that detection of the condition simultaneously triggers a suspension of data writing and an increase in a data compression ratio. As long as an acceleration threshold is not exceeded, the compressed digital video data is written to an optical disk by an optical memory system. However, when an occurrence, such as a mechanical disturbance, causes the acceleration threshold to be exceeded, data writing is suspended, because the acceleration jeopardizes the reliability of the data writing. When acceleration causes data writing to be suspended, the compressio
Garber Wendy R.
Hewlett--Packard Development Company, L.P.
Villecco John M.
LandOfFree
Method and apparatus for storing an uninterrupted digital... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for storing an uninterrupted digital..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for storing an uninterrupted digital... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3023286