Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1999-02-16
2004-03-23
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
06711344
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a data reproducing apparatus and also to a data reproducing method. More particularly, it relates to a data reproducing apparatus to be suitably used for an AV server in a broadcasting station.
2. Description of the Prior Art
The increased number of channels that have become available for accessing to various types of information due to, if partly, the development of CATV (cable television) in recent years has by turn given rise to a strong demand for novel audio/video data recording/reproducing apparatus adapted to recording and reproducing different sets of audio/video data concurrently with a single apparatus. As a matter of fact, apparatus referred to as a video server (or an AV (audio and/or video) server) and adapted to concurrently recording different sets of audio/video data in and also reproducing such data from randomly accessible recording means such as hard disks have getting popularity to meet this demand.
Generally, a video server installed in a broadcasting station is required to show a high data transfer rate and have a huge recording capacity in order to meet various requirements including a high image and sound quality and a long recording time. Thus, attempts have been made to produce a high data transfer rate and a high recording capacity by introducing a data recording/reproducing apparatus capable of dealing with a plurality of hard disks (hereinafter referred to as HD) units concurrently and storing parity data in the apparatus in advance so that the overall reliability of the apparatus may be maintained if one or more than one of the HD units fail. With such an arrangement, it is possible to realize a multi-channel video server adapted to a variety of applications such as VOD (video on demand) and NVOD (near video on demand) systems, where same source data comprising a plurality of different sets of audio/video data are recorded in a distributed fashion and then reproduced simultaneously or with slight time differences before they are transmitted through a multiple of channels.
The data recording/reproducing apparatus used in such a video server is based on the RAID (redundant arrays of inexpensive disks) technology of utilizing a plurality of hard disk drives (hereinafter referred to as HDDs), each being adapted to drive a plurality of hard disks, as described in Patterson et al. (“A Case for Redundant Arrays of Inexpensive Disks (RAID)”, ACM SIGMOND Conference, Chicago, Ill., Jun. 1-3, 1998.)
According to the above paper, the RAID technology may be classified into five categories, RAID-1 through RAID-5. Category RAID-1 used to write same data in a pair of HDDs. With Category RAID-3, the input data are divided into groups of data having a predetermined length and recorded in a plurality of HDDs, while a parity data is generated as exclusive OR of the corresponding data blocks of each HDD and written in another HDD. With Category RAID-5, on the other hand, data are divided into large units (blocks) and the data of each unit are recorded in an HDD as data block, while the outcome of exclusive OR (a parity data) of the corresponding data blocks of each HDD is recorded in other HDDs as a parity block in a distributed fashion.
For the remaining aspects of RAID, reference should be made to the above identified paper.
An AV server as described above comprises a data storage consisting of a plurality of hard disks for storing AV data, a plurality of AV data input/output interfaces (hereinafter referred to as ports) for inputting AV data into and outputting such data from the data storage and a system controller for controlling the operation of the entire system. Each port has a memory for regulating the timing of retrieving out AV data from and that of storing AV into the data storage. Then, an AV server having the above described configuration performs processing operations concurrently for a multiple of channels as the system controller controls the ports in such a way that they are used evenly and cyclically on a time division basis with a predetermined period. More specifically, each port processes AV data for a single channel on a time division basis so that, as a result, AV date are processed for all the channels simultaneously by the ports, the number of which is equal to that of the channels. Therefore, with such an AV server, time slots are allocated to the ports of the multiple of channels periodically in a rigid fashion. Then, as a general practice, the length of each time slot is made as short as possible in order to minimize the queuing time of each port, provided that the time length required for each port to read and reproduce a given volume of data from the memory at an ordinary rate is secured.
An AV server used by professionals in broadcasting stations and other similar facilities are required by necessity to show a quick responsiveness particularly in the initial stages of the AV data reproducing operation. Additionally, since AV data will have to be reproduced with variable speed for frequent high speed or reversal replaying in AV data editing sessions, a quick responsiveness and an enhanced operability are essential particularly when the replay speed has to be accelerated for a shift from normal speed to high speed or vice versa and when the current forward replaying has to be switched to backward replaying or vice versa. More specifically, when an command is given for a replay speed change, such a change has to take place very smoothly in producing the specified speed and/or running direction without giving rise to the effect of a slow-speed film.
However, with the known AV server, the length of each time slot is defined by referring to the normal replay speed and hence they are accompanied by the following problems when they are used for variable speed.
For example, in a known AV server provided 10 ports and hence adapted to perform input/output operations through 10 channels, a second is divided into 10 time slots, which are then evenly allocated to the 10 channels so that AV data for a second (30 frames) are read out in a time slot. However, the operation of reading out data at such a rate is insured only when the hard disk from which it is reading out data has a continuous recording area or several distributed areas at most for a second of operation so that the operation can proceed effectively at least for a second for reading out the specified contents.
Thus, with such a known AV server, storage areas on the currently active hard disk have to be accessed discontinuously in a high speed AV data reproduction mode of operation so that a large portion of the time dedicated to the data reproducing operation is actually consumed for the accessing process at the cost of the time necessary for reading data. More specifically, when reading AV data from the hard disk for frames selected for high speed replaying as a function of the required magnification ratio of replay speed, distributed areas have to be accessed on a frame by frame basis so that consequently AV data for only two or three frames can be read out in a single time slot in the worst case where the time is mostly consumed for seek operations.
Therefore, the above described time slot allocation scheme is not very effective and the volume of AV data that can be read out in a single time slot is reduced from the intended volume of data good for 30 frames to the volume of data good for only two or three frames. The net result is that the number of data sheets reproduced per unit time is reduced significantly particularly during high speed data reproducing operations so that images may be displayed like those of a slow-speed film and the operation of searching out any wanted image can become very cumbersome in the editing session.
Secondly, such a known AV server cannot respond to a command for an operation of accelerating from normal replaying to high speed replaying, decelerating from high speed replaying to normal replaying or reversing the reproducing direction issued by way of the control panel until
Fujita Hiroyuki
Ito Norikazu
Katsuo Satoshi
Sato Koichi
Shiga Tomohisa
Frommer William S.
Frommer & Lawrence & Haug LLP
Mahr Hans R.
Sony Corporation
Tran Thai
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