Abstract:
Digital TV system with a PVR function and method for making a stream jump therein, wherein, upon reception of a stream jump order from a user, searching the storage medium for a target GOP the user, or a system designated, changing a reproducing position to a TP next to a TP having a picture header among TPs in a prior picture positioned right forward of the searched target GOP, and starting reproduction from the changed reproducing position, thereby preventing occurrence of a decoding error while maintaining continuity of CC values in decoding TPs of a target GOP, to permit no broking of picture even in the stream jump.

Description:
[0001]    This application claims the benefit of the Korean Application No. P2001-59640 filed on Sep. 26, 2001, which is hereby incorporated by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a stream jump in a digital TV system for a personal video recorder (PVR), more particularly, to a digital TV system in which a stream jump can be made without an error of a continuity counter (CC) value, and a method for making a stream jump therein.  
           [0004]    2. Background of the Related Art  
           [0005]    Recently, amid the full scale start of digital TV (DTV) broadcasting, and spreading of DTV receivers, DTVs with various attached functions are on stage for meeting various users&#39; demands.  
           [0006]    As one of the DTV attached functions that are paid attention, the PVR function provides various reproducing function by using large capacity storage medium. As the storage medium for the PVR, a hard disk is employed, which in general provide a large capacity at a low price enough to store a long time of TV program.  
           [0007]    Basically, the PVR has no great difference from present VCR (Video Cassette Recorder) in view of providing a function for recording a program. However, since the PVR is based on a digital broadcasting signal, the PVR has features of the digital broadcasting, such as simultaneous recording of different programs, and individual program watching suit to own needs regardless of broadcasting time table of the broadcasting station. Moreover, different from the present analog VCR tape, as audio, and video information is recorded in digital data, the PVR assures a picture quality of no information loss, even after countless times of recording and reproduction. Furthermore, the PVR has a time shift function which permits the user simultaneous storage, and reproduction of a program the user watches at the present time.  
           [0008]    One of merits of the PVR is that the PVR provides a stream jump function, such as instant replay, advertisement skip, section repetition, fast forward, fast rewind, and the like during watching a program.  
           [0009]    Meanwhile, for more effective signal transmission, the digital broadcasting digitizes, and compresses various audio, video, and other attached information, and converts into a transport stream by using a multiplexer before transmission. The video is compressed according the MPEG-2 (Moving Picture Experts Group-2) algorithm, the transport stream is transmitted in packet units each with a fixed size of 188 bytes (called as TP), and decoded in the TP units at a receiver side.  
           [0010]    The MPEG-2 handles images in units of ‘picture’ (one full screen of an image), when a frame, or a field may be allocated to the picture. That is, when the frame is allocated to the picture, it is called as a frame structure, and when the field is allocated to the picture, it is called as a field structure.  
           [0011]    There are three pictures of I, P, B in forms of pictures the MPEG-2 defines. The I picture is one in which simply only the picture is subjected to DCT (Discrete Cosine Transform) for coding without motion compensation, and the P picture is one in which motion compensation is made based on an I, or other P picture, and remained difference is subjected to DCT. The B (Birdirectionally predicted-coded) is one in which though the motion compensation is made the same with the P picture, different from the P picture, the motion compensation is made from two pictures in front and rear of a time axis. Eventually, a picture sequence of the MPEG-2 has a structure like - - - ,B, B, I, B, B, P, B, B, P, B, B, - - - , wherein, in view of a sequence of display, pictures starting from the B picture two pictures ahead of the I picture to the P picture ahead of the next I picture is called as a GOP (Group Of Pictures). However, referring to FIG. 1, in view of a transmission sequence, the GOP is from an I picture to a picture ahead of the next I picture. When it is assumed that a number of pictures in the GOP is represented with ‘N’, and a number of pictures between I and P pictures, or P and P pictures is represent with ‘M’, the ‘N’ and ‘M’ values vary within one sequence. A sequence header may be inserted in a starting position of every GOP, and a picture header is inserted in a picture starting position of every picture in the GOP. That is, the picture consists of the picture header and a payload, wherein, in general, picture header information is loaded on one or two TPs, including information required for decoding data of a payload portion, and actual data of the payload portion is loaded on more than a few tens of TPs.  
           [0012]    The MPEG-2 transport stream consists of packets each with 188 bytes, each of which consists of a packet header with 4 bytes, and a payload of 184 bytes. The first byte of the packet header is a synchronization byte, having a value of 0×47 for all the packets. The packet header has a PID (Packet Identifier) number for identifying a signal on the payload. The payload has a video PES (Packetized Elementary Stream), an audio PES, and a PSI (Program Specific Information) PES. That is, a PID is provided to each video PES, each audio PES, and each PSI. Therefore, once the header information of a TP is detected, it can be known that a data at the payload of the TP of being the video PES, the audio PES, or the PSI PES. The PSI has various information provided for convenience of watchers from the broadcasting station, and video and audio PID numbers of programs of the broadcasting station.  
           [0013]    Therefore, when the watcher intends to watch a broadcasting of a particular broadcasting station, the TV receiver detects the audio, and video PID numbers for a selected broadcasting with reference to the PSI, and a demultiplxer extracts only a video signal and an audio signal having the particular PID, thereby permits the watcher to watch the video, and the audio.  
           [0014]    There is also a CC (Continuity Counter) region of 4 bits at an end part of the packet header for detecting a transmission error within the PID, where, as shown in FIG. 3, numerals starting from 0 to 15 are recorded in a progressively increasing order.  
           [0015]    If a TP is lost in the middle of transmission, since there will be a gap in the CC values which are to progressively increase, a decoded can sense an error in reception of TP, according to which an appropriate action can be taken. For an example, if the CCs are the same for two successive TPs having the same PID, it is regarded as duplication of packets, and the TP received presently is discarded. If the CC values have a difference two or more than two, it is regarded as a packet loss, the presently received TP is not decoded, but discarded, and the decoding starts from the next TP.  
           [0016]    [0016]FIG. 4 illustrates a block diagram of a related art DTV with a PVR function, schematically.  
           [0017]    Referring to FIG. 4, there is a tuner  401  for selecting a RF signal on a particular channel from signals from broadcasting stations, converting an IF signal, and providing to a demodulator  402 , and the demodulator  402  demodulates and digitizes the IF signal of the particular channel, and provides the IF signal in a transport stream (TS). The TS is provided to a buffer  406  for display, and to a PID filer  403  for storage in a storage medium  405 .  
           [0018]    The TS stored in the buffer  406  is provided to an A/V decoder  407 , and the A/V decoder  407  splits an audio stream and a video stream from the transport stream having the audio stream and the video stream multiplexed therein, decoded at respective decoders, and presented to speakers and TV screen, respectively.  
           [0019]    When it is intended to record a broadcasting signal in the storage medium  405 , the transport stream is not decoded, but recorded in the storage medium  405  directly through the PID filter  403  and a time stamp module  404 . Thereafter, when it is intended to reproduce the broadcasting signal recorded on the storage medium  405 , the transport stream stored in the storage medium  405  is respectively audio, and video decoded in the A/V decoder  407  through the time stamp module  404 , and the buffer  406 , and presented to the speakers and the TV screen, respectively.  
           [0020]    The PID filter  403  filters packets having video PIDs and audio PIDs of the program to be stored from TPs demodulated by using PID information in the header regions of the TPs, and provides to the time stamp module  404 .  
           [0021]    The time stamp module  404  inserts time stamps to the filtered video and audio transport packets for marking received times, and records on the storage medium  405 . In reproduction, the time stamp module  404  transmits reproduced TPs to the A/V decoder  407  through the buffer  406  while sustaining an exact bit rate with reference to the time stamp on the TP reproduced from the storage medium  405 . This is for prevention of a decoding error caused by overflow, or underflow of the decoder buffer. In this instance, the time stamp is removed from the reproduced TP, and transmitted to the buffer  406 . That is, the time stamp is only referred to in the reproduction.  
           [0022]    The time stamp is added to the TP to be recorded on the storage medium  405  for making a reproduction rate in a later reproduction the same with the time of initial transmission.  
           [0023]    A related art method for making a stream jump in a digital TV with a PVR function will be reviewed.  
           [0024]    In general, a method for making a stream jump in an MPEG-2 stream is a GOP (Group Of Picture) skip method, i.e., detecting a picture index of each GOP, and shifting a reproducing position to a GOP having desired information, i.e., a target GOP. As the digital broadcasting is the MPEG-2 stream too, the same method is applied to the PVR.  
           [0025]    [0025]FIG. 5 illustrates a flow chart showing the steps of a related art method for making a stream jump, and FIG. 6 illustrates an example of an actual stream jump.  
           [0026]    That is, a user inputs a stream jump order, such as instant replay, advertisement skip, section repetition, fast forward, fast rewind, and the like through a key input part  409  like a remote controller (S 501 ), a stream jump controlling part  408  searches the storage medium  405  for the target position GOP the user, or the system designates (S 502 ). Then, the stream jump controlling part  408  starts reproduction from a TP at a starting position of a target GOP (S 503 ).  
           [0027]    The target position the stream jump is to be made thereto may be designated by the user, or the system. For an example, if the stream jump order is the section repetition, the target position the jump is to be made thereto is designated by the user. However, if the stream jump order is fast forward, or fast rewind, the target position the jump is to be made thereto is designated by using information on a preset value and the present position.  
           [0028]    In the meantime, before decoding the reproduced TP, the A/V decoder  407  compares a CC value added to the reproduced TP to a CC value added to the TP at a position before making the stream jump (S 504 ), for checking continuity of the CC value (S 505 ). The continuity means a sequence of a progressively increasing numerals starting from, for an example, 0 to 15. Therefore, CC values of two TPs have a continuity, if, for an example, the CC value of the last TP is greater by ‘1’ than a CC value of a prior TP.  
           [0029]    For an example, referring to FIGS. 3 and 6, it is assumed that a stream jump order is given, when the present reproduction position is at a video TP  210  with a CC value of ‘1’ given thereto. And, the target the stream jump is to be made thereto is a GOP 2 .  
           [0030]    Then, by the user&#39;s stream jump order, the GOPs are searched, for a GOP having information meeting the order, i.e., a target GOP (GOP 2 ). Since the GOPs have picture indices different from one another for making each of the GOP distinctive, the target GOP (GOP 2 ) can be found with easy by using the picture indices.  
           [0031]    Then, the reproducing position of the PVR is shifted to a TP at a starting position of the required GOP (GOP  2 ) ( 210 → 220 ), and a scene the user desires is reproduced.  
           [0032]    If the two CC values have continuity, for an example, as shown in FIG. 3, if a CC value added to the video TP  210  prior to a stream jump is ‘1’, and a CC value added to the video TP  220  at a starting position of the target GOP is ‘2’, the reproducing video TP  220  is decoded and displayed regularly at the A/V decoder  407  (S 506 ).  
           [0033]    In the meantime, a reproducing position is shifted from on TP to another TP, which have the same PIDs, for making a stream jump, a gap of CC values occurs at a probability of 15/16. Therefore, if the steam jump is made without an appropriate disposal of the CC value gap, a general decoder produces a decoding error, and a broken picture is displayed. For an example, as shown in FIG. 3, if a CC value added to the video TP  210  prior to a stream jump is ‘1’, and a CC value added to the video TP  220  at a starting position of the target GOP is ‘6’, there is a discontinuity occurred between the two CC values of the two TPs. Then, the A/V decoder  407  discards the reproduced video TP  220  without decoding, and the required decoding and display is made starting from the next TP (S 507 ).  
           [0034]    Since the discarded video TP is a TP at a starting position of the GOP, the TP has important information, such as the picture header information. The A/V decoder  407  can not decode the picture if the A/V decoder  407  is not provided with the picture header information, but a decoding error is produced. Accordingly, a regular display can not be made, but a broken picture is displayed. Moreover, if there is an error at a picture in a particular GOP, the decoding may not be done properly, resulting to have broken pictures for the GOP.  
           [0035]    Thus, the related art method for making a stream jump has a problem of broken picture caused by shifting to a reproducing position without taking a decoder performance for the CC value of each TP into account, to produce a decoding error at a discontinuity of the CC values.  
         SUMMARY OF THE INVENTION  
         [0036]    Accordingly, the present invention is directed to a digital TV system, and a method for making a stream jump therein that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.  
           [0037]    An object of the present invention is to a digital TV system, and a method for making a stream jump therein, which can eliminate broken picture phenomenon in making a stream jump without additional device.  
           [0038]    Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.  
           [0039]    To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the digital TV system with a PVR function includes a storage medium for storing a broadcasting signal if recording, or a time shift function is set, a key input part for providing a stream jump order through a user, a stream jump controller for receiving a stream jump order from the key input part, searching the storage medium for a target GOP having the user, or a system designated, and changing a reproducing position to a TP next to a TP having a picture header among TPs in a prior picture positioned right forward of the searched target GOP, and a decoder for determining decoding of every TP starting from the TP at the reproducing position changed at the stream jump controller, and carrying out decoding according to a result of the determination.  
           [0040]    The decoder decodes, not a data on a TP at the reproducing position to a last TP in the picture because the data has no picture header information, but a data on a TP at a starting position of the target GOP.  
           [0041]    The stream jump controller receives a stream jump order from the key input part, searches the storage medium for a target GOP having the user, or a system designated, and changes a reproducing position to a TP having continuity with a CC value of a TP at a position before making a stream jump among TPs in a prior picture positioned right forward of the searched target GOP.  
           [0042]    In another aspect of the present invention, there is provided a method for making a stream jump in a digital TV with a PVR function, including the steps of (a) receiving a stream jump order from a user, (b) upon reception of the stream jump order, searching the storage medium for a target GOP the user, or a system designated, and changing a reproducing position to a TP next to a TP having a picture header among TPs in a prior picture positioned right forward of the searched target GOP, and (c) determining decoding of every TP starting from the TP at the reproducing position, and carrying out decoding according to a result of the determination.  
           [0043]    In further aspect of the present invention, there is provided 16. A method for making a stream jump in a digital TV with a PVR function, including the steps of (a) receiving a stream jump order from a user, (b) upon reception of a stream jump order from the key input part, searching the storage medium for a target GOP having the user, or a system designated, and changing a reproducing position to a TP having continuity with a CC value of a TP at a position before making a stream jump among TPs in a prior picture positioned right forward of the searched target GOP, and (c) determining decoding of every TP starting from the TP at the reproducing position, and carrying out decoding according to a result of the determination.  
           [0044]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0045]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention:  
         [0046]    In the drawings:  
         [0047]    [0047]FIG. 1 illustrates a relation between picture forms and GOPs defined in the MPEG-2;  
         [0048]    [0048]FIG. 2 illustrates an example of a structure of a transport stream packet (TP) defined in the MPEG-2;  
         [0049]    [0049]FIG. 3 illustrates an example of a CC value given to every TP in FIG. 2, and an example of a stream jump;  
         [0050]    [0050]FIG. 4 illustrates a block diagram of a related art DTV with a PVR function, schematically;  
         [0051]    [0051]FIG. 5 illustrates a flow chart showing the steps of a related art method for making a stream jump;  
         [0052]    [0052]FIG. 6 illustrates an example of a related art method for making a stream jump;  
         [0053]    [0053]FIG. 7 illustrates a flow chart showing the steps of a method for making a stream jump in accordance with a preferred embodiment of the present invention; and  
         [0054]    [0054]FIG. 8 illustrates a method for making a stream jump in accordance with a preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0055]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. FIG. 7 illustrates a flow chart showing the steps of a method for making a stream jump in accordance with a preferred embodiment of the present invention, and FIG. 8 illustrates a method for making a stream jump in accordance with a preferred embodiment of the present invention.  
         [0056]    When a user inputs a stream jump order, such as instant replay, advertisement skip, section repetition, fast forward, fast rewind, and the like, in the middle of program watch through a key input part  409 , such as a remote controller (S 701 ), a stream jump control part  408  searches the storage medium  405  for a target GOP the user, or a system designated (S 702 ). Then, the reproducing position is shifted to a picture right forward of the searched target GOP (S 703 ), and the reproduction is started from a TP next to a TP which includes a picture header within the TPs in the right forward picture (S 704 ).  
         [0057]    For an example, as shown in FIG. 8, it is assumed that the present reproducing position is a video TP ( 210 ) of a GOP 3 , a CC value given to the video TP ( 210 ) is ‘1’, and a stream jump order is given thereto. A target GOP the stream jump is to be made thereto is GOP 2 . Then, the stream jump controller  408  searches the GOPs in response to the stream jump order from the user for a GOP having information meeting the stream jump order, i.e., the target GOP (GOP 2 ), and shifts the reproducing position to a TP  330  next to a TP having a picture header among TPs in a picture right forward of the target GOP (GOP 2 ) (i.e., a last picture of GOP 1 ).  
         [0058]    That is, the TPs are provided to the A/V decoder  407  starting from a TP  330  next to the TP having a picture header among TPs of a picture right forward of the target GOP (GOP 2 ).  
         [0059]    Since the GOPs have picture indices different from one another for making a GOP distinctive from others, the target GOP (GOP 2 ) can be found by using the picture indices, with easy. Moreover, if the picture header information included in each picture is referred to, a prior picture right forward of the target GOP (GOP 2 ) can be found with easy. As the header of each TP has PID information indicating a signal carrying a payload, the TP  330  next to the TP having the picture header within a picture right forward of the target GOP (GOP 2 ) can be found with easy if the PID information is used.  
         [0060]    Meanwhile, the A/V decoder  407  makes no decoding for a picture without the picture header.  
         [0061]    Therefore, upon reception of the TP  330  next to a TP having the picture header among TPs of a picture right forward of the target GOP (GOP 2 ), the A/V decoder  407  makes no decoding for the TP  330 , but discards (S 705 ). This no decoding continues until a TP  220  at a starting position of the target GOP (GOP 2 ) is transmitted.  
         [0062]    In this instance too, the A/V decoder  407  checks a continuity of CC values before and after the decoding, which is meaningless in the present invention.  
         [0063]    That is, if the TP  330  is discarded as a discontinuity is occurred between the CC value of the TP  210  before the stream jump and the CC value of the TP  330  after the stream jump, though the CC values have a continuity starting from the next TP, since the next TP is also a TP having no picture header, the next TP is discarded without being decoded. It is because payload of one picture has at least a few tens of TPs. However, the CC values thereafter have continuities. That is, CC values of successive TPs have a continuity, the TPs of the picture are not decoded, but discarded.  
         [0064]    The foregoing process is continued until a TP  220  at a starting position of the target GOP is received.  
         [0065]    Upon reception of the TP  220  at a starting position of the target GOP, the AN decoder  407 , the A/V decoder  407  decodes and displays starting from a data of the TP  220  (S 706 ). That is, the TP  220  at the starting position of the target GOP (GOP 2 ) has the picture header information, and the CC values are continuous, decoding to the TP  220  can be made regularly.  
         [0066]    In this instance, because a picture right forward of the target GOP (GOP 2 ) is not decoded, but discarded, display signal is not presented for a while until a data of a first TP  220  of the target GOP (GOP 2 ) is reproduced. However, the reproduction time period of the region is extremely short in view of a time sequence, a signal of an actual display is sensed continuous.  
         [0067]    In conclusion, in the present invention, no decoding error is occurred regardless of the continuity of the CC values in making a stream jump.  
         [0068]    As another embodiment of the present invention, upon reception of the stream jump order, after a last TP having a continuity with a CC value of the TP before the stream jump order is made among TPs in a picture right forward of the target GOP is found, the reproduction may be made starting from the last TP. For an example, if the CC value of the TP  210  before the stream jump order is given is ‘1’, the reproduction may be made starting from a last TP with a CC value of ‘2’ among TPs in a picture right forward of the target GOP. In this instance, if the CC values in the TPs, and the PID values, are referred to, the last TP having continuity with the CC value of the TP at a position before the stream jump is made can be found among the TPs of the right forward picture, with easy.  
         [0069]    Alikely, in this instance too, the data of the last TP having no continuity with the CC value is not decoded, but discarded. This is because there is no picture header information in the picture having the last TP included thereto. However, the CC values of the video TP  210  before the stream jump is made, and the last video TP after the stream jump is made have continuity, there is no decoding error occurred even if the decoding is carried out starting from the TP  220  at a starting position of the target GOP. Since the TP at the starting position of the target GOP has header information of the GOP, and header information of the picture, and the CC values are continuous too, the decoding is made regularly.  
         [0070]    Thus, the user can watch a desired scene without an error.  
         [0071]    In the meantime, the method for making a stream jump of the present invention is applicable to other fields which are based on the MPEG-2, with easy.  
         [0072]    As has been explained, the digital TV system with a PVR function and method for making a stream jump therein of the present invention has an advantage in that no decoding error is occurred in decoding the TPs of a target GOP, though a continuity of the CC values are maintained, that is, no picture is broken even if the stream jump is made, because the reproduction is made starting from a TP next to a TP having the picture header among TPs of a picture right forward of the target GOP in making the stream jump.  
         [0073]    It will be apparent to those skilled in the art that various modifications and variations can be made in the digital TV system with a PVR function and method for making a stream jump therein of 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.