Abstract:
The present invention relates to method and apparatus of recording digital data stream on a recording medium such as a high-density digital versatile disk. The present recording method searches received digital data stream containing video signals for each picture section, packetizes a data section including at least one picture section found in the searching process into a PES (Packetized Elementary Stream) packet, slices the PES packet to make the sliced data pieces to a plurality of transport packets, and writes the plurality of transport packets within a stream object unit if the stream object unit has a space enough to store the plurality of transport packets, or from head point of a next stream object unit if not. Therefore, the head of each stream object unit is aligned with start of an arbitrary picture, thereby improving random accessibility of A/V data stream recorded on a recording medium.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to method and apparatus of recording digital data stream on a recording medium such as a high-density digital versatile disk (called ‘HD-DVD’ hereinafter).  
           [0003]    The present invention further relates a recording medium on which digital data stream has been written in accordance with said method.  
           [0004]    2. Description of the Related Art  
           [0005]    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.  
           [0006]    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 series of 188-byte-long transport packets (TPs).  
           [0007]    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 analog TV system. Furthermore, it ensures data compatibility with a digital communication device, a digital storage device, etc.  
           [0008]    In the meantime, 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 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.  
           [0009]    Digital A/V data compressed in the manner of MPEG 2 for the digital TV broadcast system are composed of I— (Intra—), P— (Predictive—), and B— (Bidirectionally predictive—) pictures. An I picture is a basic one and a P or a B picture can be presented as a video frame if there is an associated I picture.  
           [0010]    In the digital TV broadcast system, the compressed digital A/V data are divided to insert in each payload field of series of 188-byte-long (inclusive of header) TPs which are broadcasted sequentially.  
           [0011]    Then, the digital recorder would record the TPs carrying TV broadcast programs on a writable HD-DVD in the same order as they are received. During the recording operation, a predetermined-sized, e.g., 4-byte time stamp indicative of packet arrival time may be added to each TP.  
           [0012]    If the recorded TPs reaches some packs, e.g., 32 packs during the TP recording, the digital recorder groups those packs into a single ‘high-density stream object unit’ (called ‘HOBU’ hereinafter) and creates and writes search information for that HOBU as navigation data. The search information includes location or location-associated time information pointing to the head of a HOBU.  
           [0013]    However, if the broadcasted TPs are recorded in the same order as they are received as aforementioned, the head of each HOBU is not aligned with the start of an arbitrary picture as shown in FIG. 1. In case that digital data stream has been recorded as shown in FIG. 1, when the digital recorder searches the recorded digital data stream for a certain scene equivalent to a picture a user wants to view, it searches as jumping in the unit of HOBU with reference to the stored search information for all HOBUs.  
           [0014]    However, because a HOBU includes the rest data of a previous picture in its head area as shown in FIG. 1, a complete video frame can not be constructed from the data in the head area. Therefore, the digital recorder must discard the rest data of a previous picture in the current HOBU and obtain a complete picture data from successive TPs following the discard data. After the obtained complete picture data are presented as a video frame, the digital recorder may confirm whether or not reproduction is to be started from the presented picture based on user&#39;s command, e.g., ‘continue searching’ or ‘play’.  
           [0015]    However, the additional searching operation within a HOBU for a complete picture takes more searching time. Namely, it makes worse random accessibility of recorded digital data stream.  
           [0016]    If the rest data of a previous picture are outputted not discarding, noise might be generated in a video frame.  
           [0017]    Consequently, if digital data stream of digital TV broadcast programs are recorded as they received, the aforementioned disadvantages would arise inevitably.  
           [0018]    On the other hand, if a read-only HD-DVD containing A/V digital data stream to be presented through a digital television set is manufactured, without any consideration of alignment of the head of each HOBU with picture start, in the manner that digital data stream is divided and filled in each payload field of successive TPs with which HOBUs are packed, as illustrated in FIG. 1, then, such-manufactured read-only HD-DVD would still have the aforementioned drawbacks such as bad random-accessibility.  
         SUMMARY OF THE INVENTION  
         [0019]    It is an object of the present invention to provide digital data stream recording method and apparatus which packs a new HOBU with data of an arbitrary complete picture from its head point while recording the digital data stream on a recording medium as grouping predetermined size among the recorded digital data stream to a HOBU.  
           [0020]    It is another object of the present invention to provide a recording medium in which digital data stream recorded thereon are grouped to a plurality of HOBUs each of which contains data of an arbitrary complete picture from its head point.  
           [0021]    A method of recording digital data stream on a recording medium in accordance with the present invention is characterized in that it comprises the steps of searching digital data stream containing video signals for each picture section; packetizing a data section including at least one picture section found in said searching step into a first-typed packet; and slicing the first-typed packet to make the sliced data pieces to a plurality of second-typed packets, and writing the plurality of second-typed packets within a stream object unit if the stream object unit has a space enough to store the plurality of second-typed packets, or from head point of a next stream object unit if not.  
           [0022]    An apparatus of recording digital data stream on a recording medium in accordance with the present invention is characterized in that it comprises: a first packetizer searching digital data stream containing video signals for each picture section and packetizing a data section including at least one among found picture sections into a first-typed packet; a second packetizer slicing the first-typed packet made by said first packetizer to make the sliced data pieces to a plurality of second-typed packets; and a data writer writing the plurality of second-typed packets made from the first-typed packet by said second packetizer within a stream object unit if the stream object unit has a space enough to store the plurality of second-typed packets, or from head point of a next stream object unit if not, wherein data of every second-typed packet are converted to writing suitable format by said data writer before written on a recording medium.  
           [0023]    A recording medium in accordance with the present invention is characterized in that it includes data recorded thereon are grouped into a plurality of stream object units, wherein the stream object unit begins with start data of a picture equivalent to a video frame.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    The accompanying drawings, which are included to provide a further understandings of the invention, illustrate the preferred embodiments of the invention, and together with the description, serve to explain the principles of the present invention.  
         [0025]    [0025]FIG. 1 shows an example of data format formed by a conventional recording method in which transport stream is recorded as received;  
         [0026]    [0026]FIG. 2 is a block diagram of an embodiment of a digital recorder recording digital data stream on a writable medium in accordance with the present invention; and  
         [0027]    [0027]FIG. 3 shows a schematic process of recording received A/V data stream in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0028]    In order that the invention may be fully understood, a preferred embodiment thereof will now be described with reference to the accompanying drawings.  
         [0029]    [0029]FIG. 2 is a block diagram of an embodiment of a digital recorder recording digital data stream on a writable medium in accordance with the present invention.  
         [0030]    The digital recorder of FIG. 2, which may be a video disk recorder (called ‘VDR’) being able to write digital A/V data on a writable HD-DVD, comprises an A/V stream converter  10  converting received A/V signal to A/V data stream compressed according to MPEG 2 standard; an A/V stream separator  11  separating the compressed A/V data stream into audio and video stream; a PES packetizer  12  packetizing the audio and the video stream into PES (Packetized Elementary Stream) packets defined in MPEG 2 standard, respectively; a TS packetizer  13  slicing the video and the audio PES packets, respectively, to make respective series of TPs, and multiplexing the respective series of video and audio TPs into a single TS; a writing processor  14  re-formatting the TS from the TS packetizer  13  to record/reproduction suitable structure and outputting disk writing signals corresponding to re-formatted data; an optical pickup  15  forming marks and spaces along a track of an inserted writable HD-DVD according to the disk writing signals; and a controller  17  receiving information on data size being written, creating search information based on the received information, and writing all of the created search information on the writable HD-DVD  16  through the writing processor  14 .  
         [0031]    The A/V stream converter  10 , if a digital TV broadcast program formatted in TS is received, extracts compressed A/V data stream from the TS through decoding successive TPs. However, if non-MPEG formatted program stream broadcasted by other standard of digital TV broadcast system, e.g., DirecTV is received, the A/V stream converter  10  conducts decoding algorithm suitable to that system to extract A/V data, and compresses the extracted A/V data again according to data compressing rule of MPEG 2 standard. If an analog A/V signal is received, the A/V stream converter  10  digitizes audio and video signal, respectively, and conducts MPEG 2 compressing operation for the respective digitized signal.  
         [0032]    [0032]FIG. 3 shows a schematic process of recording received A/V data stream in accordance with the present invention.  
         [0033]    A received data stream of an arbitrary format is converted to MPEG 2-compressed data stream  301  by the A/V stream converter  10 . Then, the PES packetizer  12  at the next stage analyzes video stream of the A/V data stream  301  to search for every I—, P—, and B—picture section, and composes a PES packet with at least one picture section. The PES packetizer  12  also composes a PES packet with audio data stream of each frame group.  
         [0034]    At this time, a PES header is added at the front of each PES packet to form a complete PES packet. A Presentation Time Stamp (PTS) for a picture included in a PES packet is written in a PES header thereof. A Decoding Time Stamp (DTS) for an included picture is optionally written in a PES header.  
         [0035]    Through the above operations, the PES packetizer  12  outputs a data stream  302  shown in FIG. 3.  
         [0036]    When the PES packetizer  12  transmits the composed data stream  302  to the TS packetizer  13 , it also sends a ‘PES packet start signal’ (PPSS) indicative of transmission of start data of a video PES packet, in the strict sense, PES header of a video PES packet to the TS packetizer  13 . The TS packetizer  13  slices the video and the audio PES packets, respectively, to make two series of video and audio TPs, and multiplexes the video and the audio TPs into a single TS  303  which is depicted in FIG. 3.  
         [0037]    If the PPSS is received from the PES packetizer  12  while making TPs from received data, the TS packetizer  13  starts to insert just-received data in payload field of the next video TP, namely, it creates a new TP and writes data received concurrently with the PPSS in the created new TP. If a current video TP is not fully filled with received data at the time when the PPSS is received, its remaining area is padded with null data. The elliptic zones  303   a  in FIG. 3 show partially null-padded TPs through the above operations of the TS packetizer  13 .  
         [0038]    The TS packetizer  13  delivers TPs to the writing processor  14  in the same order as they are multiplexed. If a TP being delivered at present contains start data of a sliced PES packet, then the TS packetizer  13  notifies the writing processor  14  of that fact by sending PES starting TP signal (PSTS) concurrently to the writing processor  14 .  
         [0039]    The writing processor  14  gathers the received TPs. Whenever the PSTS is received from the TS packetizer  13 , the writing processor  14  checks whether or not TPs gathered until now are larger than the size of a single HOBU, a grouping unit of the writable HD-DVD  16 . If not greater, the writing processor  14  only memorizes the location, e.g., ‘SB i ’ of a TP received at the same time as the PSTS, and continues to gather the TPs received thereafter. If greater, for example, if current case is at ‘SB i+1 ’, the writing processor  14  re-formats the gathered TPs excluding back TPs placed from a previously-memorized position ‘SB i ’ to form writing data group for a single HOBU, and modulates and outputs the formed writing data group.  
         [0040]    The size of writing data group formed for a single HOBU is less than the capacity of a single HOBU because of the exclusion of back TPs which would cause, if included in the writing data group, the whole gathered TPs to exceed the capacity of a HOBU. Therefore, the writing processor  14  generates additional null data of which size is equal to the remaining capacity of a HOBU. The generated null data follows the outputted writing data group and are written in the remaining area of the HOBU. The null data padded in the HOBU are sure to prevent possible reproducing or decoding errors.  
         [0041]    Next successive TPs are gathered to the remaining TPs not included in the formed writing data group for a HOBU, namely, TPs existing from the previously-memorized position ‘SB i ’ to the just-received position ‘SB i+1 ’ and the latest TP received concurrently with the PSTS, and they will be written in the next HOBU when the gathered size is greater than the capacity of a single HOBU. Consequently, the next HOBU will also begin with start data of a picture, in the strict sense, header of a PES packet of which data field begins with start data of a picture.  
         [0042]    The modulated signals outputted from the writing processor  14  are written in the form of marks and spaces on the writable HD-DVD  16  through the optical pickup  15 .  
         [0043]    In the meantime, after forming the writing data group for a single HOBU, the writing processor  14  informs the controller  17  of the writing data group formation for a single HOBU and the number of the PSTSs received until the writing data group formation.  
         [0044]    On the other hand, the controller  17  continuously receives and stores PTSs written in the PES header of each PES packet by the PES packetizer  12 . Thus, if the writing data group formation for a single HOBU is informed along with the number of the PSTSs, the controller  17  calculates a PTS time length of the present writing data group formed for a single HOBU based on the stored PTSs of every PES packet to create search information for that HOBU. The search information may include PTS time length of each HOBU and accumulated PTS time length up to each HOBU (it need not size information and accumulated size information of each HOBU if the size of a HOBU is constant). The search information will be created for each HOBU-sized data, and it is transmitted to the writing processor  14  to be written on a pre-assigned area as navigation data in the middle of A/V data recording operation or after A/V data recording is done.  
         [0045]    According to the explained writing operation of the writing processor  14 , the received A/V data stream forms a data written format  304  on the writable HD-DVD  16  as shown in FIG. 3.  
         [0046]    In other words, the head of each HOBU is aligned with the start data of a PES packet, namely, the start of an arbitrary picture.  
         [0047]    Therefore, when the controller  17 , in search mode, identifies a certain HOBU using the navigation data and accesses the identified HOBU, an additional minute searching operation for a picture start is not necessary because the start of the identified HOBU is exactly a picture start.  
         [0048]    The above-explained data stream recording format  304  of FIG. 3 is applicable to a read-only HD-DVD which stores A/V data stream in the form of pre-pits. Namely, A/V data stream is formed on a read-only HD-DVD in the manner that each HOBU begins with picture start data. In addition, search information for each HOBU is recorded in a navigation data area or as a navigation data file.  
         [0049]    Needless to say, an additional minute searching operation in a HOBU for a picture start is removed for a such-manufactured read-only HD-DVD.  
         [0050]    On the other hand, when A/V data stream is written on a conventional read-only DVD, it is packetized into PES packets in the manner that one PES packet is written in one sector.  
         [0051]    However, in the present A/V stream recording method, a stream section including at least one picture, of which size is quite larger than that of a sector of a conventional read-only DVD, is packetized into one PES packet. Therefore, the number of PES headers added to each PES packet is reduced considerably in comparison with the A/V data stream recording scheme conducted for a conventional read-only DVD.  
         [0052]    The above-explained A/V data stream recording method and apparatus, and a recording medium in which A/V data stream has been recorded through said method can improve random accessibility of recorded A/V data stream and increase the actual data recording efficiency of a high-density recording medium in comparison with recording format of a conventional read-only DVD.  
         [0053]    It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.