Patent Publication Number: US-2006002260-A1

Title: Information recording device

Description:
BACKGROUND OF INVENTION  
      1. Field of the Invention  
      The present invention relates to an information recording device, and in particular to a device that compresses and records video data.  
      2. Related Art  
      Conventional recording devices are able to receive the signal of an analog broadcast selected by a user and record program data that has been digitally converted and encoded to recording media such as hard disk.  
      In view of restrictions on the storage area in recording media, Japanese Patent Application Publication No. 2003-339016, for example, discloses a record/playback method that, during playback, compresses recorded data that has been played back at a lower bit rate than the recording bit rate, and records the compressed data to the recording medium.  
      According to this record/playback method, once all the played data of a given program has been compressed, the compressed data is available for playback and the storage area of the pre-compression recorded data is released, enabling the storage area on disk to be used effectively.  
      However, with this record/playback method, the pre-compression recorded data cannot be erased until the compression is completely finished, meaning that the storage area cannot be released for further recording. Thus in the case of time-shift playback, for example, in which recorded sections of a program are played back while the program is being recorded, the storage area of recorded data cannot be released part way through the compression.  
     SUMMARY OF INVENTION  
      The present invention, which was arrived at in view of the above problem, aims to provide an information recording device that allows the storage area of pre-compression program data to be released without waiting for compression to be completed.  
      To resolve the above problem, the present invention is an information recording device for compressing video data constituting a video stream read from a recording medium storing reference information that shows a storage location of the video data and is referred to in order to read the video data as the video stream. The information recording device includes: a reading unit operable to read part of the video data; a compressing unit operable to compress the read data and record the compressed data to the recording medium; and an updating unit operable, when the compressed data is recorded, to update the reference information to show the storage location of the compressed data rather than the read data.  
      According to this structure, the reference information is updated every time program data that has been played back is compressed and recorded, so that the compressed program data is read instead of the pre-compression program data. As a result, the pre-compression program data is no longer referred to during playback. Since the storage area of the pre-compression program data may then be freely overwritten with other program data, the above structure enables this storage area to be applied as free area when compressing and recording subsequent program data.  
      Here, the video data may consist of plural pieces of split video data, the reference information may show a storage location of each piece of split video data and a reference order of the storage locations, the read video data may be a piece of the split video data, and the updating unit may update the reference information when the compressed split data is recorded to show the storage location of the compressed split data rather than the read split data.  
      According to this structure, the program data has been split before being recorded, making it possible to perform the compressing/recording in units of split data, to update the reference information to refer to the compressed split data instead of the pre-compression split data whenever split data is compressed and recorded, and to release the storage area as free area per piece of split data.  
      Here, at least one piece of the split video data may include duplication information that indicates a certifier relating to duplication of the piece of split video data, and the information recording device may further include: a certification requesting unit operable, if the read split data includes the duplication information, to send a certification request to and receive a response from the certifier; and a control unit operable to control the compressing and recording by the compressing unit according to the received response.  
      According to this structure, if information relating to a certifier (i.e. copyright holder etc.) is included in the received program data, a certification request can be sent to the certifier in regard to duplicating program data that has been played back, and a response received from the certifier. If the response indicates COPY FREE, for example, the program data can be compressed and recorded at a compression rate selected by the user, whereas if the response indicates COPY ONCE, the program data can be erased after being compressed at a low bit rate.  
      The information recording device may further include: a capacity judging unit operable to judge whether a free capacity of the recording medium is at or below a prescribed threshold; and a recording unit operable to record video data constituting an externally acquired video stream to the recording medium together with the reference information, and if judged in the affirmative during recording of the video stream, the reading unit, the compressing unit and the updating unit may perform the reading, compressing/recording and updating on video data of the video stream being recorded.  
      According to this structure, if the free area on the recording medium falls below a prescribed capacity during the recording of a program, for example, data designated from the video data of the program being recorded can be compressed so as to release the storage area for further recording.  
      Here, each piece of split video data may include all or part of one of plural types of programs and classification information indicating the type of the program, and the compressing unit may change the compression rate at which the read split data is compressed depending on the classification information included therein.  
      According to this structure, content information indicating either “program content” or “CM” can be recorded per piece of split data, in the case of program data that includes program content data and CM data, for example, having been split before being recorded, thus enabling split data that has been played back to be compressed at a high compression rate if relating to a CM, and thereby increasing the free area by minimizing the storage area taken up by CM data.  
      Here, at least one piece of the split video data may include data that requires updating, the reading unit may include an acquiring subunit operable to judge whether the read split data include data that requires updating, and to externally acquire update data if judged in the affirmative, and the compressing unit may compress and record the read split data after replacing the data that requires updating with the acquired update data.  
      According to this structure, if recorded program data that includes CM data also includes information indicating the CM provider, for example, the latest CM data can be acquired from the provider and played back in place of the original CM data, and this replacement CM data can then be compressed and recorded after playback. Thus whenever the program is played back, the user is able to view the latest information, and the CM provider is able to provide the user with the latest information. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
      These and other objects, advantages, and features of the invention will become apparent from the following description thereof taken in conjunction with the accompanying drawings, which illustrate specific embodiments of the present invention.  
      In the drawings:  
       FIG. 1  is a structural view showing an embodiment 1 of an information recording device  20  pertaining to the present invention;  
       FIG. 2A  shows a structure and an exemplary content of encoding information;  
       FIG. 2B  shows a structure and an exemplary content of header information;  
       FIG. 2C  shows a structure and an exemplary content of link information  200  for individual programs;  
       FIG. 3  is a flowchart of processing by a split recording unit  23 ;  
       FIG. 4  shows an overview of the processing performed by information recording device  20  on split data recorded on a fixed disk  24 ;  
       FIG. 5  is a flowchart of processing by a playback unit  25 ;  
       FIG. 6  is a flowchart of processing by a compression unit  26 ;  
       FIG. 7  is a flowchart of processing by an erase unit  27 ;  
       FIGS. 8A-8C  demonstrate the change in the storage area of fixed disk  24  when split data is played back and compressed and link information is updated by information recording device  20 ;  
       FIG. 9  is a structural view showing an embodiment 2 of information recording device  20  pertaining to the present invention;  
       FIG. 10  is a flowchart of processing by a certification request unit  29 ; and  
       FIG. 11  is a flowchart of processing by compression unit  26  when split data includes content information. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
     Embodiment 1  
      The following description relates to an embodiment 1 of an information recording device pertaining to the present invention.  
      Synopsis  
      The information recording device receives the data of broadcast programs (hereinafter “program data”) from an external source, and records split data derived by splitting encoded program data into units of fixed length to a fixed disk. The information recording device also records link information showing both the storage location of each piece of split data and the playback order of the split data in a specific area of the fixed disk.  
      The link information for managing the storage area of the fixed disk is referred to when recording data to and reading data from disk. Storage area not shown in the link information is treated as area freely available for further recording of program data (hereinafter “free area”).  
      When the user instructs the playback of a program recorded on the fixed disk, the information recording device sequentially reads and decodes split data constituting the program with reference to the link information, and outputs the decoded data to a monitor. The information recording device also compresses the decoded data to reduced the data size, records the compressed data to free area on the fixed disk, and updates the link information when the recording is performed to show the storage location of the compressed split data instead of the storage location of the pre-compression split data.  
      Structure  
       FIG. 1  is a structural view showing an embodiment 1 of an information recording device  20  pertaining to the present invention. The device structure is described in detail below with reference to  FIG. 1 .  
      Information recording device  20  is constituted from an analog-to-digital converter (ADC)  21 , an encoding unit  22 , a split recording unit  23 , a fixed disk  24 , a playback unit  25 , a compression unit  26 , an erase unit  27 , and a digital-to-analog converter (DAC)  28 .  
      ADC  21  functions to convert broadcast signals received via a tuner  10  to digital signals. The received signals are here assumed to include signals showing broadcast programs selected by the user as well as an electronic program guide (EPG).  
      Encoding unit  22  functions to encode program data digitally converted by ADC  21 , and send the encoded data to split recording unit  23 . MPEG is used here as the encoding scheme, and the encoding is performed at a bit rate shown in preset encoding information (described later).  
      Split recording unit  23  functions to receive encoded program data in a write buffer (not depicted), and record program data equal to the buffer capacity as a single piece of split data to free area on fixed disk  24  with reference to link information  200  (described later). Split recording unit  23  also functions to enter the storage locations of split data in link information  200  per program in the playback order.  
      Fixed disk  24  is a hard disk, a digital versatile disc (DVD) or similar recording medium.  
      Playback unit  25  functions to receive a user instruction to playback a program recorded on fixed disk  24 , read split data constituting the program to a read buffer (not depicted) in accordance with link information  200 , and decode the program data in the read buffer in units of split data. Playback unit  25  also functions to output the decoded split data to DAC  28 , as well as to send the decoded split data to compression unit  26  together with the storage location.  
      Compression unit  26  functions to receive decoded split data from playback unit  25 , compress the decoded data at a lower bit rate than the decoded data, and record the compressed split data to fixed disk  24 .  
      Here, compression involves initially decoding and then re-encoding the split data at a bit rate shown in preset encoding information (described later) to reduce the data size, the re-encoding being performed at a lower bit rate than the pre-decoding data. MPEG is used here, although other encoding schemes may be applied provided the data size is reduced. Compression unit  26  sends information showing the storage location of the compressed split data (hereinafter “post-compression storage location”) and the storage location of the pre-compression split data (hereinafter “pre-compression storage location”) to erase unit  27 .  
      Erase unit  27  functions to replace the pre-compression storage location with the post-compression storage location in link information  200  of the program relating to the pre-compression split data.  
      DAC  28  functions to convert decoded split data output from playback unit  25  to analog signals, and output the analog signals to monitor  30 .  
      Monitor  30  is a liquid crystal display (LCD) etc. that functions to display analog signals sent from DAC  28 .  
      Data  
      Table data recorded in information recording device  20  is described next using  FIGS. 2A  to  2 C.  
       FIG. 2A  shows a structure and an exemplary content of encoding information  50  referred to by encoding unit  22  when encoding program data and by compression unit  26  when compressing split data.  
      Encoding levels  51  in encoding information  50  are corresponded with bit rates  52  as shown in  FIG. 2A .  
      Here, encoding levels  51  express encoding and compression levels, while bit rates  52  show encoding and compression bit rates.  
      Encoding information  50  prerecorded on fixed disk  24  or in a memory such as shared ROM (not depicted) is read by encoding unit  22  when encoding program data and by compression unit  26  when compressing split data decoded by playback unit  25 .  
       FIG. 2B  shows a structure and an exemplary content of header information  100  for both program data encoded by encoding unit  22  and split into units of fixed length by split recording unit  23 , and split data compressed by compression unit  26 .  
      IDs  110  in header information  100  are corresponded with compression frequencies  120 , encoding levels  130  and data  140  as shown in  FIG. 2B .  
      Here, IDs  110  are identifiers for uniquely identifying individual pieces of split data and compressed split data, and are appended whenever split data or compressed split data is generated by either split recording unit  23  or compression unit  26 .  
      Compression frequencies  120  show the number of times that compression unit  26  has compressed respective pieces of split data and compressed split data.  
      Encoding levels  130  show the value of encoding levels  51  in encoding information  50  at which split data and compressed split data were either encoded or compressed by encoding unit  22  and compression unit  26 .  
      Data  140  showing the correspondence between IDs  110  and split data/compressed split data is included to facilitate description.  
      Header information  100  is generated whenever split recording unit  23  records split data, read whenever compression unit  26  compresses decoded split data, and again generated whenever compression unit  26  records compressed split data.  
       FIG. 2C  shows a structure and an exemplary content of link information  200  for program data recorded on fixed disk  24 , in which program titles  210  are corresponded with data  220 , viewing flags  230  and storage locations  240  as shown in  FIG. 2C .  
      Program titles  210  show titles acquired from an EPG for programs selected for recording by the user.  
      Data  220  showing the correspondence between program titles  210  and split data/compressed split data is included to facilitate description.  
      Viewing flags  230  indicate whether the split data and compressed split data of data  220  have been read from fixed disk  24  by playback unit  25  and played back.  
      Storage locations  240  show the addresses in fixed disk  24  of individual pieces of split data and compressed split data, and are linked in playback order using a list structure. Note that in  FIG. 2C  the playback order is from the top.  
      Link information  200  is updated by split recording unit  23  when split data is recorded and by erase unit  27  when compression unit  26  records compressed split data.  
      Operations  
      The operations of information recording device  20  are described next.  
      Information recording device  20  receives input of program data for encoding from an external source via tuner  10 , encodes the received program data, splits the encoded program data into units of fixed length, and records the split data to fixed disk  24 .  
       FIG. 3  is a flowchart of processing by split recording unit  23 . These operations are described next in conjunction with  FIG. 3 .  
      Upon receiving a record instruction from the user (step S 51 ), split recording unit  23  reads link information  200  and enters the program title acquired from an EPG received with the program data (step S 52 ).  
      Split recording unit  23  receives the program data encoded by encoding unit  22  in a write buffer, and generates header information (step S 53 ). Split recording unit  23  judges whether the write buffer is full (step S 54 ), and continues to receive program data from encoding unit  22  until the write buffer is full. When the buffer is full (step S 54 =YES), split recording unit  23  generates end information (step S 55 ), and records the program data to which the header information and end information is appended to fixed disk  24  as a single piece of split data. When recording the split data, split recording unit  23  enters the storage location in association with program title  210  in link information  200  in the playback order (step S 56 ).  
      Operations performed when the user instructs playback of a program recorded on fixed disk  24  are described next using the  FIG. 4  flowchart.  
      Upon receiving a user selection of a title of a program recorded on fixed disk  24  (step S 11 ), information recording device  20  reads link information  200  for the program from fixed disk  24  (step S 12 ).  
      Playback unit  25  sequentially reads split data constituting the selected program based on the read link information  200  and plays back the read data (step S 13 ).  
      Compression unit  26  compresses split data that has been played back and records the compressed data to fixed disk  24  in parallel with the processing by playback unit  25  (step S 14 ). Erase unit  27  updates the link information by replacing pre-compression storage locations with post-compression storage locations in parallel with the processing by compression unit  26  (step S 15 ).  
      The above processing operations are described in detail below using  FIGS. 5, 6  and  7 .  
       FIG. 5  is a flowchart of processing by playback unit  25 .  
      Playback unit  25  reads split data corresponding to the program title selected for playback to a read buffer based on link information  200  (step S 21 ), decodes the read data in units of split data, and outputs the decoded data to monitor  30  via DAC  28  (step S 22 ).  
      Playback unit  25  then updates viewing flag  230  in link information  200  of the decoded split data to “1” (step S 23 ), and sends the decoded data and corresponding header information  100  to compression unit  26  (step S 24 ).  
       FIG. 6  is a flowchart of processing by compression unit  26 .  
      Upon receiving decoded split data and corresponding header information  100  from playback unit  25  (step S 31 ), compression unit  26  reads encoding information  50  and selects an encoding level corresponding to a bit rate that is lower than the bit rate corresponding to encoding level  130  shown in header information  100  (step S 32 ).  
      Compression unit  26  then compresses the decoded split data at the bit rate corresponding to the selected encoding level (step S 33 ), and generates header information  100  showing compression frequency  120  and encoding level  130  for the compressed data (step S 34 ).  
      Following step S 34 , compression unit  26  records the compressed split data and generated header information  100  to fixed disk  24  (step S 35 ), and sends header information  100  for both the pre-compression split data and compressed split data to erase unit  27  (step S 36 ).  
       FIG. 7  is a flowchart of processing by erase unit  27 .  
      Upon receiving header information  100  for both the split data and compressed split data sent from compression unit  26  at step S 36  (step S 41 ), erase unit  27  reads link information  200  from fixed disk  24 , and replaces storage location  240  of the split data with the storage location of the compressed split data (step S 42 ).  
      The storage area of split data whose storage location was replaced at step S 42  of the above update processing is treated as free storage area on fixed disk  24 , enabling split data and compressed split data to be newly recorded.  
     WORKING EXAMPLE  
      The above processing operations are described next using the example given in  FIGS. 2A-2C  and  8 A- 8 C in conjunction with  FIGS. 5, 6 , and  7 .  
       FIGS. 8A  to  8 C demonstrate the change in the storage area of fixed disk  24  when the user instructs playback of a program  1  entered in program title  210  of link information  200  ( FIG. 2C ). The rectangular boxes  300 ,  301  and  302  each represent fixed disk  24 , and “DATA (UNPLAYED)” in  FIG. 8A  shows the individual pieces of data entered in data  220  of  FIG. 2C .  
      In  FIG. 5 , playback unit  25 , upon receiving a user instruction to playback program  1 , reads link information  200  of program  1 , and reads the split data constituting program  1  in order to the read buffer starting from data  1 - 1  (step S 21 ).  
      Playback unit  25  then decodes data  1 - 1  read to the read buffer, and outputs decoded data  1 - 1  to monitor  30  via DAC  21  (step S 22 ).  
      Following step S 22 , playback unit  25  updates viewing flag  230  of data  1 - 1  in link information  200  of program  1  to “ 1 ” (step S 23 ), and sends decoded data  1 - 1  and header information  100  of data  1 - 1  to compression unit  26  (step S 24 ).  
      The above processing is repeated for data  1 - 2  to  1 - 4  until a user instruction to end playback is received.  
      In  FIG. 6 , compression unit  26 , upon receiving decoded data  1 - 1  and header information  100  from playback unit  25  (step S 31 ), reads encoding information  50 , and selects encoding level  2  corresponding to a lower bit rate than encoding level  1  of data  1 - 1  (step S 32 ).  
      Following step S 32 , compression unit  26  compresses decoded data  1 - 1  at 4 Mbps, which is the bit rate corresponding to selected encoding level  2  (step S 33 ), and generates header information showing compression frequency “1” and encoding level  121  for compressed data  1 - 1  (step S 34 ).  
      Compression unit  26  records compressed data  1 - 1  and the newly generated header information to fixed disk  24  (step S 35 ), and sends both the header information of data  1 - 1  and the newly generated header information to erase unit  27  (step S 36 ).  
      In  FIG. 7 , erase unit  27 , upon receiving both header information  100  of data  1 - 1  ( FIG. 2B ) and the header information of compressed data  1 - 1  (step S 41 ), updates the link information of program  1  by replacing the storage location of data  1 - 1  with the storage location of compressed data  1 - 1  (step S 42 ).  
       FIG. 8B  shows a state in which data  1 - 2  has been processed in the same manner as data  1 - 1 , and compressed data  1 - 1  and compressed data  1 - 2  have been recorded to fixed disk  24  during the playback of data  1 - 3 , thus releasing the storage area of data  1 - 1  and data  1 - 2  for further recording as free area  320 .  
       FIG. 8C  shows a state in which data  1 - 3  and data  1 - 4  have also been fully processed, thereby creating expanded free area  325 .  
     Embodiment 2  
      The following description relates, in the case of certifier information showing a certifier for certifying the duplication of a program being appended to received program data, to an embodiment in which an information recording device transmits a certification request to the certifier based on the certifier information, and compresses/records split data that has been played back according to whether the duplication has been certified.  
       FIG. 9  is a structural view showing an embodiment 2 of information recording device  20  pertaining to the present invention.  
      As shown in  FIG. 9 , information recording device  20  of embodiment 2 is constituted from a certification request unit  29  and a LAN interface  40  in addition to the structure of  FIG. 1 , and can be connected to an external server  41  via LAN interface  40 .  
      Certification request unit  29  functions to send a certification request relating to the duplication of split data to external server  41  via LAN interface  40  based on certifier information, and to receive response information relating to the certification request from external server  41  and send the response information to compression unit  26 .  
      Note that received program data is here assumed to have certifier information denoted by a URL appended thereto, and split recording unit  23  is assumed to generate header information  100  that includes the certifier information and record the header information to fixed disk  24  together with the split data whenever split data is recorded.  
      Operations  
      Operations performed by certification request unit  29  based on certifier information are described below using  FIG. 10 .  
      Playback unit  25  reads split data and header information relating to a program title selected by a user from fixed disk  24 , and sends the read data and header information to certification request unit  29 .  
      Upon receiving the header information from playback unit  25  (step S 61 ), certification request unit  29  judges whether the header information includes certifier information (step S 62 ).  
      If judged to include certifier information (step S 62 =YES), certification request unit  29  transmits a certification request to external server  41  via LAN interface  40  based on the certifier information in order to request the certifier to certify duplication of the split data (step S 63 ).  
      If a copy certification certifying the duplication is received from external server  41  (step S 64 =YES), certification request unit  29  accepts selection of an encoding level ( FIG. 2A ) from the user (step S 66 ), and instructs compression unit  26  to compress the split data at the selected encoding level.  
      Upon receiving information such as COPY ONCE indicating that duplication is not certified (step S 64 =NO), certification request unit  29  instructs compression unit  26  to compress the split data at a lower bit rate than the split data (step S 65 ).  
      Variations  
      The following description relates to variations of embodiment 1 of information recording device  20  pertaining to the present invention.  
      Variation 1  
      In embodiment 1, split data that has been played back is targeted for compression, although if the free area falls below a prescribed threshold during the recording of program data by split recording unit  23 , compressed split data recorded on fixed disk  24  may be designated for further compression, and the processing of compression unit  26  and erase unit  27  performed on the designated data.  
      In this case, split recording unit  23  judges whether the free area on fixed disk  24  is at or below a prescribed threshold, and notifies compression unit  26  of the judgment result if judged in the affirmative.  
      Upon receiving an affirmative judgment result from split recording unit  23 , compression unit  26  reads link information  200 , reads encoding information  50  and header information  100  for each piece of compressed split data whose viewing flag is “1”, designates those pieces of compressed split data whose encoding level  130  is other than “5” as data for compressing, and compresses/records the designated data.  
      Note that in the case of compressed split data being targeted for compression, compressed split data whose encoding level is other than “5” may be prioritized in ascending order of the encoding frequencies.  
      Variation 2  
      In embodiment 1, compression unit  26  compresses decoded split data at a lower bit rate than the bit rate of encoding level  130  in corresponding header information  100 , although the encoding level may be varied according to the type of program included in the split data.  
      For example, if non-program content (e.g. commercial messages) is recognized by the attribute of audio signals included in split data being “stereo” and program content is recognized by the audio attribute being “monaural”, the program type of a piece of split data is set to “program content” when it is program content that the split data includes.  
      In this case, split recording unit  23  appends content information to the header information of individual pieces of split data that shows whether the split data includes program content or non-program content. Here, it is assumed that the encoding bit rate is preset depending on whether the content information shows program content or non-program content, and that the bit rate in the case of non-program content is set lower than for program content.  
      Note that split recording unit  23  may split the program data into segments corresponding to program content and segments corresponding to non-program content.  
      The following description using  FIG. 11  relates to processing by compression unit  26  to set the encoding level based on content information included in header information received from playback unit  25 .  
      Upon receiving the header information of decoded split data from playback unit  25  (step S 71 ), compression unit  26  reads the content information (step S 72 ), and judges whether the content information shows program content (step S 73 ).  
      If judged in the affirmative (step S 73 =YES), compression unit  26  sets the compression rate for program content (step S 74 ), and if judged in the negative (step S 73 =NO), compression unit  26  interrupts the compression processing (step S 75 ), sets the compression rate for non-program content, recommences the compression processing, and sends a signal instructing playback unit  25  to restart playback (step S 76 ). The compression rate is maintained at the non-program content rate until the split data whose content information shows non-program content has been processed (step S 77 =YES), at which point the compression rate is set for program content (step S 74 ).  
      Additional Remarks  
      The present invention, which has been described above based on embodiments 1 and 2 of an information recording device, is of course not limited to these embodiments. The following modifications are also possible.  
      (1) Compression unit  26  performs the compression in the preferred embodiments, although encoding unit  22  may be used if the same encoding as that performed by encoding unit  22  is applied as the compression scheme. In this case, playback unit  25  sends decoded split data to encoding unit  22 , which switches from receiving input from ADC  21  to playback unit  25 , and performs encoding in order to compress the decoded data. This structure enables hardware costs to be cut by sharing processing blocks.  
      (2) In the preferred embodiments, encoded program data is split into fixed units and recorded to fixed disk  24 , although the program data may be recorded to fixed disk  24  without being split into fixed units.  
      In the case of only part of a program being played back, for example, playback unit  25  reads corresponding program data from fixed disk  24 , and stores the recording start and end positions in memory when the program data has been read. Compression unit  26  compresses and records the decoded program data sent from playback unit  25 , and generates header information for the compressed program data when the recording is performed. Erase unit  27  generates link information that causes both the post-compression storage location of the compressed data to be read instead of the recording start position in memory, and the recording end position in memory to be read after the post-compression storage location of the compressed data.  
      (3) If data that requires updating (e.g. commercial messages) is included in received program data together with information showing the CM provider, information recording device  20  may acquire update data from the CM provider when the program data is played back, and substitute the latest CM data.  
      In this case, split recording unit  23  splits the program data into segments corresponding to commercial messages and segments corresponding to program content depending on whether the program data relates to commercial messages or program content, and appends content information to the header information for individual pieces of split data as in the above variation  2 .  
      Playback unit  25  acquires the latest CM data from the CM provider when the content information in header information for split data read from fixed disk  24  shows CM, replaces the split data with the acquired CM data, and plays back the latest CM data.  
      Compression unit  26  compresses and records the decoded latest CM data received from playback unit  25 .  
      (4) In the preferred embodiments, the write buffer capacity is used as the criterion for splitting program data, although program data equal to a unit of capacity other than buffer capacity or program data received in the write buffer over a fixed time period may be treated as split data.  
      (5) In the preferred embodiments, split data decoded by playback unit  25  is compressed at a bit rate corresponding to an encoding level higher by one level than the encoding level of the split data, although the decoded split data may be compressed at any encoding level or at an encoding level selected by the user provided the bit rate used is lower than the original bit rate.  
      (6) In the above variation  1 , compression unit  26  targets compressed split data recorded on fixed disk  24  for further compression in the case of free area on fixed disk  24  falling below a prescribed threshold during the recording by split recording unit  23  of split data constituting a program. However, program data received in the write buffer or recorded split data of the program being recorded may be designated for compression. In this case, compression unit  26  compresses the designated data at a lower bit rate than that used by encoding unit  22 , and sets the compression frequency in corresponding header information to “1”.  
      (7) In the preferred embodiments, all of the compressed split data is recorded to fixed disk  24 , although compressed data may be recorded to a portable device such as a DVD. In this case, information relating to the portable device is added to the link information. In the case of copy control information (e.g. COPY ONCE) being appended to received program data, the program data may be recorded to the portable device after being compressed at a higher compression rate than the original program data, and the original data erased.  
      (8) A computer program for having a processor execute the processing operations ( FIGS. 3, 5 ,  6 ,  7 ) performed by an information recording device pertaining to the present invention can also distributed by either being recorded on a recording medium for circulation or being circulated via any of various types of communication channels. Exemplary recording media include IC cards, hard disk, optical disks, flexible disks, and ROM. The distributed computer program can then be submitted for use by being stored in a processor-readable memory or the like, and the functions of an information recording device pertaining to the present invention realized by the processor executing the computer program.  
      Note that an information recording device pertaining to the present invention can be used by being loaded in hard disk recorders, DVD recorders, and the like.  
      Although the present invention has been fully described by way of examples with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Therefore, unless such changes and modifications depart from the scope of the present invention, they should be construed as being included therein.