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Method and apparatus of recording/reproducing multi-channel stream

Method and apparatus of recording/reproducing multi-channel stream description/claims

The present invention relates to method and apparatus that records/reproduces a multi-channel stream to/from a recording medium such as a high-density DVD (Digital Versatile Disk).

Owing to technical improvement in the fields of video/audio data compression, digital modulation/demodulation, and so on, a digital television broadcast system broadcasting TV signals in the form of digital data stream is being standardized rapidly.

In the digital television broadcast system, audio/video (A/V) signals to be broadcasted are compressed according to the data compressing rule specified by MPEG 2 (Moving Picture Experts Group) and the compressed A/V data are broadcasted in the form of transport stream (TS), which is also defined in MPEG 2 standard, composed of successive 188-byte-long transport packets (TPs).

The digital TV broadcast system, which will be commercialized soon owing to technical improvement of A/V data compression and transmission, is able to support much higher-quality of video and audio than an analog TV system. Furthermore, it ensures data compatibility with a digital communication device, a digital storage device, etc.

By the way, a new device is being developed to prepare for commercialization of digital TV broadcast system. That is a digital recorder being able to receive TS of digital broadcast programs and to record it on a writable HD-DVD. Such a digital recorder will be widely used as the digital TV broadcast system is commercialized in earnest.

A single physical broadcast channel (called ‘RF channel’ in general) has about 6 MHz bandwidth which ensures 19.4 Mbps data rate. This data rate can carry a single HD-TV broadcast signal or about four SD-TV signals. Such a logical or virtual channel carrying one SD-TV signal in an RF channel is called ‘sub-channel’.

In other words, a single RF channel sometimes includes several digital channels, namely, sub-channels which carry mutually-different broadcast programs. Therefore, a DVD recorder being developed must be able to record/reproduce two or more sub-channels simultaneously at a user's request. In addition, it may be able to record/reproduce two or more sub-channels chosen from different RF channels, respectively.

By the way, an apparatus being able to receive and present digital TV broadcast programs, e.g., a digital TV set can not select a sub-channel and decode a received RF stream until PSI (Program Specific. Information) for a digital stream of TV program is received. Moreover, it can keep an exact presentation timing of packets constituting a digital stream after synchronizing an internal clock with PCRs (Program Clock Reference) where respective PCRs carried by the digital stream are received within an allowable interval.

In general, a digital recorder records one channel and reproduces it later. In case that a digital recorder is able to record a plurality of channels, it may reproduce one channel chosen among recorded channels, or reproduce at least two channels simultaneously to present them in a multi-screen, e.g., PIP (Picture-In-Picture) on a digital TV set.

In this multi-channel providing, PSI providing way must be differentiated and PCRs inserted in each channel stream may be compensated depending upon whether all multi channels belong to a single RF channel or not.

It is an object of the present invention to provide a PSI recording method for a plurality of channels that records PSI about a plurality of recorded channels to enable later individual or simultaneous presentation of the recorded channels on a display machine such as a digital TV set.

It is another object of the present invention to provide a PSI transmitting method that transmits PSI recorded along with a plurality of channels to enable later simultaneous presentation thereof on a display machine such as a digital TV set.

It is another object of the present invention to provide a time-information providing method that provides time information of a plurality of recorded channels to enable later simultaneous presentation thereof on a display machine such as a digital TV set.

A method of recording a multi-channel stream in accordance with the present invention is characterized in that it selects a plurality of sub-channels from a tuned broadcast channel, copies PSI packets included in a stream of the tuned broadcast channel into every stream of the selected plural sub-channels if the plurality of sub-channels are in same broadcast channel, records the sub-channels onto a recording medium, and writes information on whether the recorded sub-channels belong to same broadcast channel or not.

A method of reproducing a multi-channel stream in accordance with the present invention is characterized in that it checks whether a plurality of channels reproduced from a recording medium belong to same broadcast channel or not, removes PSI packets included in a channel or channels except one channel if the plural channels belong to same broadcast channel, reconstructs new PSI packets based on information of PSI packets included in respective stream of said channels to replace the existing PSI packets and compensates PCRs adequately if the plural channels belong to different broadcast channels, and multiplexes the stream of the plural channels to output.

The above-characterized multi-channel stream recording/reproducing method can provide a digital display machine set with PCRs and PSI suitable for a plurality of sub-channels chosen from one RF channel or mutually-different RF channels, thereby eliminating errors in channel selection or presentation timing in a digital display machine. Consequently, multi-screen, e.g., PIP displaying is ensured through stable decoding of multi channels.

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