Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1999-06-11
2003-05-27
Boccio, Vincent (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000
Reexamination Certificate
active
06571050
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for recording/reproducing video data using a memory; and more particularly, managing use of the memory.
2. Brief Description of the Prior Art
Unlike ordinary continuous video cassette recorders which record every frame of video signals, some video cassette recorders such as an intermittent video recording/reproducing apparatus (e.g., a time-lapse video cassette recorder (VCR)) intermittently record frames of a real video signal. For example, a time-lapse VCR receives video signals from several video cameras or the like, and intermittently records frames of the video signal on a magnetic tape at a pre-selected regular interval. As a result, the recorder drives a loaded tape to run and stop repeatedly. These time-lapse VCRs have been used in various areas requiring long recording times such as security monitoring systems in banks and museums.
As shown in
FIG. 1
, the conventional time-lapse video cassette recorder comprises a video decoder
100
which extracts a luminance signal (Y) and chrominance signal (C) from the composite analog video signals from external cameras and converts them into the digital video signals respectively; a video compressor
200
which compresses the converted digital video signals; a memory
300
in which the compressed video data are stored sequentially; a data compressor
400
which decompresses the digital video data read out from the memory
300
; a bus
902
which allows communication between the compressor
200
, the memory
300
, and the de-compressor
400
; a video encoder
500
which reconverts the decompressed digital video signals into the luminance signal and chrominance signal and synthesizes these signals into a composite analog video signal; a digital signal processor (DSP)
600
for processing digital signals in the course of compression, decompression, and memory reading/writing operations; a recording/reproducing unit
800
which records the reconverted composite analog video signals on a storage media such a magnetic tape and reproduces the recorded video signals from the storage media; and a controller
700
which supervises the aforementioned overall functions.
Furthermore, as shown in
FIG. 1
, the recording/reproducing unit
800
comprises a reproducing unit
810
which reproduces the signals modulated for recording on the magnetic tape; a deck
820
which drives mechanical elements and runs the magnetic tape forward or backward; and a recording unit
830
which records the composite analog video signals on the magnetic tape.
In addition, two switches designated SW
1
and SW
2
are shown in FIG.
1
and they change their signal path depending upon the mode set by the controller
700
.
As shown in
FIG. 2
, the memory
300
comprises a buffer memory
310
, which stores the compressed video data temporarily, and a frame memory
320
, which sequentially receives the video data stored temporarily in the buffer memory
310
, stores the video data, and then sends the video data to the decompressor
400
via the buffer memory
310
and the bus
902
when the number of frames of video signals sequentially stored in the frame memory
320
equals its maximum storage capacity.
The method for reproducing the intermittently recorded video signals with the time-lapse video cassette recorder configured as above is explained below in detail with reference to
FIGS. 1 and 2
. When a user inputs a time-lapse mode reproduction command, the controller
700
drives the deck
820
to pull out a tape into a loading state. After the tape is loaded, the deck
820
runs the magnetic tape at normal speed, which means to travel forward a frame-distance in one second, while the reproducing unit
810
reproduces the video signals recorded on the tape. In this case, the distance the magnetic tape is moved for reproducing depends on the storage capacity of the memory
300
.
The video decoder
100
separates the reproduced composite analog video signal into the luminance component signal (Y) and the chrominance component signal (U, V). The separated component signals are sampled, converted into digital data streams, and then sent to the video compressor
200
.
Under the control of the DSP
600
, each of video signals converted into a digital data stream is processed according to a predetermined compression algorithm by the video compressor
200
. The compressed digital data streams are stored sequentially in the frame memory
320
on a frame-by-frame basis via the buffer memory
310
.
When the number of frames sequentially stored in the field memory
320
reaches the maximum storage capacity of the memory
320
, the digital video signals stored in the frame memory
320
are read frame-by-frame, under the control of the DSP
600
as controlled by the controller
700
, at a regular interval according to the time lapse mode present by the user. The digital video signals read out are decompressed and restored to their original size, and then transmitted to the encoder
500
by the decompressor
400
.
Furthermore, the controller
700
controls the video encoder
500
to synthesize the luminance and chrominance component signals of the decompressed digital video streams into a composite analog video signal, which is the same as the composite video signal received from an external video camera. At the same time, the controller
700
controls the switch SW
2
to change the signal path from recording connection to reproducing connection, therefore the exterior monitor displays the video signals at the regular interval.
On the other hand, when the amount of data to be read in the frame memory
320
becomes less than or equal to a predetermined threshold value in the course of reading data from the frame memory
320
, the controller
700
controls the recording/reproducing unit
800
to start reproducing the recorded signal next to the signal last reproduced. The video data streams converted from this newly reproduced signal are buffered in the buffer memory
310
. When the reading of data stored in the frame memory
320
is complete, the data stream buffered in the buffer memory
310
is transmitted into the frame memory
320
and is read out again. As long as the buffer memory
310
is large enough, the above explained method makes it possible to eliminate the delay time which could occur between successive reproducing steps.
Furthermore, the video cassette recorder configured as above can accomplish backward reproducing of the recorded video signals through almost the same procedure. The backward reproduction (i.e., replay in reverse) process further includes the following steps. The controller
700
drives the deck
820
to move the tape in reverse at first. After backward movement, the tape is driven to move forward while the recorded signal is reproduced and stored in the memory
300
. These steps are then repeated with each rewinding of the tape positioning the tape so the next set of reproduced frames are earlier in time than the previously reproduced set of frames. In backward reproduction, the tape cannot be reproduced while driven in reverse and produce digital video data representing replay in reverse.
In the case of intermittent recording of the video signals received from the external cameras using the time-lapse video cassette recorder configured as in
FIG. 1
, the video signals being received are buffered in real time in the buffer memory
310
, and the buffered video signals are intermittently selected at a specific interval in units of a frame, and then transferred into the frame memory
320
. When the amount of frames sequentially stored in the frame memory
320
reaches a maximum storage capacity of the frame memory
320
, the controller
700
controls the DSP
600
to output the stored video signal consisting of luminance and chrominance components to the video encoder
500
, and to cause the video encoder
500
to synthesize the two signal components into the composite analog video signal. The reading/reproducing unit
800
records the syn
Birch & Stewart Kolasch & Birch, LLP
Boccio Vincent
LG Electronics Inc.
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