Television – Special applications – Manufacturing
Patent
1997-01-10
1998-08-11
Kostak, Victor R.
Television
Special applications
Manufacturing
348 13, 39520047, 455 31, H04N 710
Patent
active
057934126
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a data transmission apparatus which is suitably used in a video-on-demand or other apparatus which can send video data in response to demand at any time.
BACKGROUND ART
Realization of a practical video-on-demand (VOD) system which can instantly provide program data in response to a demand of a receiver has been desired. A VOD system able to individually respond to demands made at all times, however, requires an extremely large sized data transmission apparatus which performs complex processing.
Accordingly, a near-video-on-demand (NVOD) system which can simplify the configuration of the data transmission apparatus while realizing a function similar to that of a VOD system has been proposed. An NVOD system is a system that transmits program data to a plurality of channels at predetermined time intervals. It selects the channels for the programs starting from the next time zone or time period in response to requests made in a certain time zone and then provides those programs.
Even in an NVOD system, however, it is necessary to simultaneously reproduce a plurality of series of program data to be transmitted to a plurality of channels, so there is a desire that the reproduction of the plurality of series of program data be carried out by a simpler apparatus and by a more efficient method.
As a fundamental method of generating a plurality of series of program data, there is the method of providing a separate reproducing apparatus for each of the channels and transmitting the data to the plurality of channels by these. Further, in recent years, hard disc devices, magneto-optic disc devices, and other randomly accessible recording apparatuses which have large capacities and can perform high speed access have been realized. An NVOD system which records video data etc. in these recording apparatuses and transmits the data to the plurality of channels in a time division manner is disclosed in Japanese Patent Application No. 5-328349 previously filed by the present applicant.
Further, the present applicant has proposed in Japanese Patent Application No. 6-137018 an NVOD system with a method of recording data wherein continuous regions are read so as to read the data and transmit the data to a plurality of channels at a speed as high as possible.
In such a data transmission apparatus, however, to perform high speed access and to facilitate the control as much as possible, the data has been encoded with a predetermined fixed data rate. As a result, the encoding at the fixed compression rate is carried out even with respect to data that can be encoded with a higher compression rate than the fixed data rate, so there is a problem that the programs cannot be efficiently stored. Further, with respect to data for which encoding at a fixed compression rate is difficult, conversely the encoding is forcibly carried out at that fixed compression rate, so there is a problem that the quality of the picture and sound when reconstructing the data is deteriorated.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a data transmission apparatus using a recording apparatus recording video data, audio data, and other data encoded at a variable data rate suited to the respective data, reading the data at a high speed from that recording apparatus, and able to almost simultaneously transmit data to a plurality of channels in response to demand. Further, another object is to provide a data transmission apparatus which can store a variety of data with a high efficiency and does not cause a deterioration of quality when reconstructing the data.
When accessing a recording medium in which data is recorded at a variable data rate, the access must be carried out while checking the magnitude of the data and the head position of the data, so the access per second cannot be carried out at a high speed. Accordingly, if direct decision of the divisions of the data etc. without having to perform computations and other processing each time were made possible, access of
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patent: 5481543 (1996-01-01), Veltman
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Frommer William S.
Kostak Victor R.
Sony Corporation
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