Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1998-12-03
2002-08-20
Tran, Thai (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C386S349000
Reexamination Certificate
active
06438314
ABSTRACT:
TECHNICAL FIELD
This invention relates to a recording and reproducing device suitable for application to a variable-velocity playback type digital video recording and reproducing device capable of performing smooth and good-response variable-velocity reproduction, and a method of reproducing video information on a variable-velocity basis.
BACKGROUND ART
A digital video recording and reproducing device using a hard disk is normally large in memory capacity and needs a long access time. An information reading system using buffer memories provided in two-bank configurations has been adopted to reduce this access time. In the present system, video information is read from the other of one pair of general-purpose buffer memories when video information is written into one of the pair. Thus, the switching between the writing of the video information into one buffer memory and the reading of the video information from the other buffer memory is periodically done to sequentially record and reproduce or play back the video information. A dual port memory is known as a memory device for implementing such functions on a unitary basis.
FIG. 8
is a conceptional view showing a configuration of this type of digital video recording and reproducing device. In
FIG. 8
, a write and read-only controller
2
is electrically connected to a hard disk
1
so as to perform such control as to read video information corresponding to continuous m frames from video information corresponding to n frames. A keyboard
5
is electrically connected to the controller
2
to provide instructions for a playback velocity for video information through the use of a search dial SA provided in the keyboard
5
.
Buffer memories
3
A and
3
B provided in two-bank configurations are electrically connected to the controller
2
. Video information is read from the hard disk
1
in accordance with a reproduce or playback velocity and alternately written into the buffer memories
13
A and
13
B. In order to locate the start of an image or picture, for example upon video editing work executed by using this type of digital video recording and reproducing device, the image must be normally played back slowly. At this time, the image is reproduced at an arbitrary playback velocity (corresponding to a velocity given by an operator) less than or equal to a one-time velocity.
This playback velocity is specified or designated by the search dial
5
A. A playback circuit
4
is electrically connected to the output-stage sides of the buffer memories
3
A and
3
B so that video information alternately read from the buffer memories
3
A and
3
B is reproduced. In this type of recording and reproducing device, the video information is read from each of the buffer memories
3
A and
3
B based on a bank period or cycle T to simplify an algorithm wherever practicable. The bank cycle T indicates a period in which the video information is written into or read from each of the buffer memories
3
A and
3
B.
Operation in a one-time velocity playback mode will next be described. First, an operator designates a playback velocity. Video information is read into the buffer memory
3
A from the hard disk
1
in frame units at the designated playback velocity. At this time, video information corresponding to m frames are collectively read from the hard disk land written into the buffer memory
3
A.
When the writing of the video information into the buffer memory
3
A is completed, the bank cycle T is switched to another as shown in FIG.
9
. The bank cycle T is always constant regardless of the playback velocity designated by the operator and is changed every m frames. With its changeover, the writing of video information into the buffer memory
3
B is started and at the same time the reading of video information from the buffer memory
3
A to the playback circuit is started. The video information read from the buffer memory
3
A is reproduced by the playback circuit
4
.
Further, when the writing of the video information into the buffer memory
3
B and the reading of the video information from the buffer memory
3
A are completed, the bank cycle T is switched to another. With its switching, the reading of video information from the buffer memory
3
B is started and at the same time the writing of video information into the buffer memory
3
A is started. The video information read from the buffer memory
3
B is reproduced by the playback circuit
4
.
Thus, the video recording and reproducing device using the buffer memories
3
A and
3
B provided in the two-bank configurations has a feature in that if a one-time velocity playback mode is adopted, video information can be sequentially recorded and reproduced without depending on an expensive dual port memory.
On the other hand, when an arbitrary playback velocity (including a still playback zero velocity) less than or equal to a one-time velocity is designated, a frame skip or jump will occur upon bank switching.
When the operator locates the start of a picture or image through the use of the search dial
5
A, for example, a playback velocity less than or equal to a one-time velocity is designated. Video information is read into each of the buffer memories
3
A and
3
B from the hard disk
1
in frame units in accordance with this playback velocity. However, the playback velocity designated by the operator varies every moment for video retrieval. Further, a long access time is required to read the video information from the hard disk
1
to the buffer memories
3
A and
3
B in the frame units.
Therefore, a considerable time is required until the video information is outputted to the playback circuit
4
since the operator has designated the playback velocity. Thus, a problem arises in that variable-velocity reproduction very poor in response would be made.
In the conventional recording and reproducing device as well, the switching between the buffer memories
3
A and
3
B is performed every m frames on the basis of the bank cycle T regardless of the playback velocity.
Even when, for example, a video start portion approaches and at this time, it is desired to further sequentially read the video information of one buffer memory
3
A without depending on the previously-designated playback velocity in order to slowly play back the video information thereof, the buffer memory
3
A is switched over to the buffer memory
3
B.
Therefore, the video information stored in the other buffer memory
3
B must be read into the playback circuit
4
for slow reproduction in spite of the fact that it is desired to read the video information corresponding to the same frames into the playback circuit
4
from the buffer memory
3
A. Thus, video information corresponding to continuous frames are not read from the buffer memories
3
A and
3
B and video information corresponding to discontinuous or skipping frames are outputted to the playback circuit
4
. This offers a problem that a so-called frame skip or jump occurs and hence smooth slow reproduction cannot be achieved.
Thus, when reading control is performed while an algorithm for determining frames for video information to be written into the buffer memories
3
A and
3
B from the hard disk
1
and an algorithm for determining frames for video information to be outputted to the playback circuit
4
from the buffer memories
3
A and
3
B are being associated with one another, the frame units to be handled differ from each other between the writing of the video information to the buffer memories
3
A and
3
B and the reading of the video information from the buffer memories
3
A and
3
B, whereby the conventional variable-velocity playback system will result in a very complex one.
With the foregoing problems in view, it is therefore an object of the present invention to provide a recording and reproducing device capable of eliminating the occurrence of frame jumps upon bank switching even if an externally-instructed playback velocity varies every moment, and a method of reproducing video information on a variable-velocity basis.
DISCLOSURE OF THE INVENTION
A recording
Frommer William S.
Frommer & Lawrence & Haug LLP
Sony Corporation
Tran Thai
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