JP2008311703A - Digital catv system, transmitter and receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that image quality degradation becomes notable depending on the kind of images when a compression rate is uniformly increased in order to cope with long-time recording. <P>SOLUTION: The digital CATV system includes: a digital CATV transmitter provided with a digital broadcast reception part for receiving digital broadcast signals, a modulation and conversion part for modulating and converting the digital broadcast signals, and a compression rate detection and addition part for detecting the compression rate for not generating the notable image quality degradation in the digital broadcast signals inputted from the digital broadcast reception signals, adding the compression rate to digital CATV signals after modulation and conversion inputted from the modulation and conversion part and transmitting the information of the compression rate; and a digital CATV receiver provided with a compression rate separation part for inputting the digital CATV signals to which the compression rate is added and separating the compression rate, a first compression system decoding part for decoding the digital CATV signals, a first compression system encoding part for compressing the signals decoded by a first compression system using the compression rate, and a recording part for recording the compressed first compression system code signals. Each digital broadcast signal is recorded at the optimum compression rate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a digital CATV transmission device, a reception device, and a system for receiving and recording a video signal transmitted by digital CATV (cable television) modulation conversion.

In order to record and play back digital broadcasts, digital CATV receivers for CATV systems that have a built-in recording unit (such as a hard disk) or can be externally connected have been commercialized. Conventional digital CATV receivers of CATV systems are compressed to some extent at the stage of the material to be broadcast TS, and most of them record the broadcast TS as it is. In some products, the recording time is lengthened, so when recording and reproducing video and audio signals in the recording unit of the digital CATV receiver, it is converted into a MPEG2 signal that is compressed at a lower rate than the broadcast TS, H. has a higher compression rate than the MPEG2 system. Recording is performed after compression at a lower rate than the broadcasting system, such as encoding using the H.264 system. In this case, the digital CATV system has a problem that if the compression is performed at a lower rate than the broadcasting system, the image quality is significantly deteriorated depending on the type of the video signal. (For example, see Patent Document 1)
Hereinafter, a conventional example will be described with reference to the drawings.

  FIG. 5 is a block diagram of a conventional digital CATV system.

  The conventional digital CATV system includes a digital CATV transmission device 700, a transmission path 750, a digital CATV reception device 800, and a display device 850.

  In the digital CATV system, the digital CATV transmission apparatus 700 receives a digital broadcast by each digital reception unit, performs modulation conversion, and outputs a 64QAM signal to the transmission path 750. Digital CATV receiving apparatus 800 receives a 64QAM signal from transmission line 750, performs a channel selection demodulation process on a desired program, and outputs a video / audio signal to display apparatus 850.

  Further, the configuration of each device of the digital CATV system will be described in detail.

  The digital CATV transmitting apparatus 700 includes a BS digital receiving unit 701, a CS digital receiving unit 702, a terrestrial digital receiving unit 703, a BS digital transmitter unit 711, a CATV Remux unit 712, a terrestrial digital transmitter unit 713, and 64QAM modulation. Part 720.

  BS digital reception section 701 receives a BS-IF signal from a BS digital reception antenna (not shown), performs demodulation processing, and outputs a TS signal to BS digital transmitter section 711.

  The BS digital transmitter unit 711 receives the TS signal from the BS digital reception unit 701, processes the satellite distribution descriptor into a CATV distribution descriptor, and outputs it to the 64QAM modulation unit 720.

  CS digital receiving section 702 receives a CS-IF signal from a CS digital receiving antenna (not shown), performs demodulation processing, and outputs a TS signal to CATV Remux section 712.

  The CATV Remux unit 712 receives the TS signal from the CS digital receiving unit 702, selects a program to be transmitted for CATV, rewrites the satellite distribution descriptor to the CATV distribution descriptor, and performs a service ID rewrite process. , 64QAM modulation unit 720.

  The terrestrial digital reception unit 703 receives a terrestrial digital RF signal from a terrestrial digital reception antenna (not shown), performs demodulation processing, and outputs a TS signal to the terrestrial digital transmitter unit 713.

  The terrestrial digital transmitter unit 713 receives the TS signal from the terrestrial digital reception unit 703, processes the terrestrial digital distribution descriptor into a CATV distribution descriptor, and outputs it to the 64QAM modulation unit 720.

  The 64QAM modulation unit 720 processes the distribution descriptor for the digital CATV signal from the BS digital transmitter unit 711 and the distribution descriptor for the digital CATV signal from the CATV Remux unit 712, and combines the service ID of the service ID. The CS digital TS signal subjected to the rewriting process and the terrestrial digital TS signal obtained by processing the distribution descriptor for the digital CATV signal are input from the terrestrial digital transmitter unit 713, 64QAM modulation processing is performed, frequency multiplexing processing is performed, and output to the transmission line 750 To do.

  The digital CATV receiving apparatus 800 includes a channel selection unit 801, a TS decoding unit 802, an MPEG2 decoding unit 803, a compression rate designation unit 804, a recording unit 805, an MPEG2 encoding unit 806, and a TS encoding unit 807. Has been.

  The channel selection unit 801 receives a 64QAM signal from the transmission line 750, selects a frequency at which a desired program exists, demodulates the 64QAM signal, and outputs the TS signal to the TS decoding unit 802 and the recording unit 805.

  The TS decoding unit 802 receives a TS signal from the channel selection unit 801 or the recording unit 805, and outputs an MPEG2 video stream and an MPEG2 audio stream of a desired program to the MPEG2 decoding unit 803.

  The MPEG2 decoding unit 803 receives the MPEG2 video stream and MPEG2 audio stream from the TS decoding unit 802, performs MPEG2 decoding processing, and outputs the video signal and audio signal to the display device 850 and the MPEG2 encoding unit 806.

  The compression rate designation unit 804 designates a compression rate when the user records in the recording unit 805 using a remote controller or a main body button in advance using a graphical user interface.

  The MPEG2 encoding unit 806 inputs the compression rate from the compression rate specifying unit 804 and the video signal and the audio signal from the MPEG2 decoding unit 803, and MPEG2 encodes the video signal and the audio signal according to the compression rate from the compression rate specifying unit 804. Process and output to TS encoding section 807.

  The TS encoding unit 807 receives the MPEG2 video stream and the MPEG2 audio stream from the MPEG2 encoding unit 806, performs TS encoding processing, and outputs them to the recording unit 805.

The recording unit 805 receives a TS signal from the channel selection unit 801 or the TS encoding unit 807 and performs recording processing. Then, the recording unit 805 outputs the recorded TS signal to the TS decoding unit 802 when receiving an instruction to reproduce the recorded TS signal.
Japanese Patent Laid-Open No. 10-066038

  In the conventional technique, in order to extend the recording time, it is necessary to increase the recording medium capacity or to uniformly increase the compression rate for recording. However, in a digital CATV receiver having a recording / playback function in a digital CATV system, increasing the capacity of the recording medium increases the product cost, or if the compression rate is increased uniformly, the deterioration of the image becomes significant during playback. was there.

  In order to solve this problem, a digital CATV transmission device, a reception device, and a system according to the present invention include a digital broadcast reception unit that receives a digital broadcast signal, a modulation conversion unit that modulates and converts the digital broadcast signal, and a digital broadcast reception unit. Compression rate detection that detects a compression rate that does not cause noticeable image quality degradation in a digital broadcast signal input from a digital broadcast signal, and adds the compression rate to the digital CATV signal after modulation conversion input from the modulation conversion unit and transmits the compression rate information A digital CATV transmitting apparatus including an adding unit, a compression rate separating unit that receives a digital CATV signal with an added compression rate and separates the compression rate, a first compression scheme decoding unit that decodes the digital CATV signal, and a compression A first compression method encoding unit for compressing a signal decoded by the first compression method using a rate, and a recording for recording the compressed first compression method code signal It has a digital CATV receiver including a recording with the optimum compression ratio for each digital broadcast signal.

  According to the digital CATV transmission device, the reception device, and the system of the present invention, the digital video signal before modulation conversion by the CATV transmission device is not uniformly increased in compression rate, but is significantly deteriorated for each digital video signal. Determine the compression ratio that does not cause Then, the compression rate obtained by the CATV transmission device is added to the digital CATV signal and transmitted. In the digital CATV receiving apparatus, by performing compression recording using the compression rate for each video signal separated from the digital CATV signal, no significant image degradation occurs, and the recording unit has a higher compression rate than the original digital CATV signal. By recording, it is possible to configure a digital CATV system that extends the recording time without increasing the capacity of the recording medium.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a configuration diagram of a digital CATV system according to Embodiment 1 of the present invention.

  The digital CATV system includes a digital CATV transmission device 100, a transmission line 150, a digital CATV reception device 400, and a display device 450.

  In the digital CATV system, when each digital broadcast signal is modulated and converted into CATV digital by the digital CATV transmission apparatus 100, a compression rate that does not cause significant image degradation is added to each video signal for output to the transmission line 150. To do. Digital CATV receiving apparatus 400 receives a 64QAM signal from transmission line 150, performs a channel selection demodulation process on a desired program, and outputs a video / audio signal to display apparatus 450.

  Further, the configuration of each device of the digital CATV system will be described in detail.

  The digital CATV transmitting apparatus 100 includes a BS digital receiving unit 101, a CS digital receiving unit 102, a terrestrial digital receiving unit 103, a BS digital transmitter unit 111, a CATV Remux unit 112, a terrestrial digital transmitter unit 113, and a compression rate. The detection adding unit 120 is configured.

  BS digital reception section 101 receives a BS-IF signal from a BS digital reception antenna (not shown), performs demodulation processing, and outputs a TS signal to BS digital transmitter section 111 and compression rate detection addition section 120.

  The BS digital transmitter unit 111 receives the TS signal from the BS digital receiving unit 101, processes the satellite distribution descriptor into a CATV distribution descriptor, and outputs it to the compression rate detection / addition unit 120.

  The CS digital reception unit 102 receives a CS-IF signal from a CS digital reception antenna (not shown), performs demodulation processing, and outputs a TS signal to the CATV Remux unit 112 and the compression rate detection addition unit 120.

  The CATV Remux unit 112 receives a TS signal from the CS digital receiving unit 102, selects a program to be transmitted for CATV, rewrites the satellite distribution descriptor to the CATV distribution descriptor, and performs a service ID rewrite process. And output to the compression rate detection adding unit 120.

  The terrestrial digital reception unit 103 receives a terrestrial digital RF signal from a terrestrial digital reception antenna (not shown), performs demodulation processing, and outputs a TS signal to the terrestrial digital transmitter unit 113 and the compression rate detection addition unit 120.

  The terrestrial digital transmitter 113 receives the TS signal from the terrestrial digital receiver 103, processes the terrestrial digital distribution descriptor into a CATV distribution descriptor, and outputs the CATV distribution descriptor to the compression rate detection / addition unit 120.

  The compression rate detection / addition unit 120 receives the TS signal from the BS digital reception unit 101 and the CATV TS signal from the BS digital transmitter unit 111. Similarly, a TS signal is input from the CS digital receiving unit 102, and a CATV TS signal is input from the CATV Remux unit 112. A TS signal is input from the terrestrial digital receiving unit 103 and a TS signal for CATV is input from the terrestrial digital transmitter unit 113. Then, the compression rate detection / addition unit 120 obtains a compression rate that does not cause significant image quality degradation of each video signal of the CATV TS signal, and outputs each of the BS digital transmitter unit 111, the CATV Remux unit 112, and the terrestrial digital transmitter unit 113. A process of adding a compression rate to the signal is performed, the signal is modulated into a 64QAM signal of the CATV modulation method, and frequency-multiplexed, and then a 64QAM signal as a video signal is transmitted to the transmission line 150.

  The digital CATV receiving apparatus 400 includes a channel selection unit 401, a TS decoding unit 402, an MPEG2 decoding unit 403, a compression rate separation unit 404, a recording unit 405, an MPEG2 encoding unit 406, and a TS encoding unit 407. ing.

  The channel selection unit 401 receives a 64QAM signal from the transmission line 150, selects a frequency at which a desired program exists, demodulates the 64QAM signal, and outputs the TS signal to the TS decoding unit 402 and the recording unit 405.

  The TS decoding unit 402 receives a TS signal from the channel selection unit 401 or the recording unit 405, and outputs an MPEG2 video stream and an MPEG2 audio stream of a desired program to the MPEG2 decoding unit 403 and the compression rate separation unit 404.

  The MPEG2 decoding unit 403 receives the MPEG2 video stream and the MPEG2 audio stream from the TS decoding unit 402, performs MPEG2 decoding processing, and outputs the video signal and audio signal to the display device 450 and the MPEG2 encoding unit 406.

  The compression rate separation unit 404 receives the MPEG2 video stream from the TS decoding unit 402, separates the compression rate added by the digital CATV transmission apparatus 100, and outputs it to the MPEG2 encoding unit 406.

  The MPEG2 encoding unit 406 receives the compression rate and the video signal and audio signal corresponding to the compression rate from the compression rate separation unit 404 from the MPEG2 decoding unit 403, and performs the MPEG2 encoding process on the video signal and the audio signal according to the compression rate. And output to the TS encoding unit 407.

  The TS encoding unit 407 receives the MPEG2 video stream and the MPEG2 audio stream from the MPEG2 encoding unit 406, performs encoding processing on the TS signal, and outputs the TS signal to the recording unit 405.

  The recording unit 405 receives the TS signal from the channel selection unit 401 or the TS encoding unit 407 and performs recording processing. When the recording unit 405 receives an instruction to reproduce the recorded TS signal, the recording unit 405 outputs the recorded TS signal to the TS decoding unit 402. When only temporary recording is performed, as in time-shift playback such as so-called chasing playback, a TS signal is output from the channel selection unit 401 to the recording unit 405 to perform temporary recording, and from the recording unit 405 after a user's desired time. This can be realized by outputting the recorded TS signal to the TS decoding unit 402, outputting the TS signal to the MPEG2 decoding unit 403 after the TS decoding process.

  The display device 450 receives the video signal and the audio signal from the MPEG2 decoding unit 403, and outputs the video and the audio.

  Next, processing for adding a compression rate in the digital CATV transmission apparatus 100 will be described.

  FIG. 2 is a configuration diagram of the compression rate detection / addition unit according to the first embodiment of the present invention. Here, a description will be given of an example of processing 103 channels of BS digital signals in a BS digital broadcast channel processing block.

  The compression rate detection / addition unit 120 includes a compression rate detection / addition unit 200 in units of channels corresponding to the number of channels transmitted by the digital CATV system.

  The channel-by-channel compression rate detection / addition unit 200 includes a first TS decoding unit 201, a motion vector comparison unit 202, a second TS decoding unit 203, a sequence header generation unit 204, a TS encoding unit 205, a compression rate table 206, The 64QAM modulation unit 207 is configured.

  The first TS decoding unit 201 receives the 103-channel TS signal from the BS digital reception unit 101, performs TS decoding processing, and outputs the MPEG2 video stream to the motion vector comparison unit 202.

  The compression rate table 206 holds values obtained from statistical processing in advance for each compression method, a compression rate that does not cause significant image degradation in the video signal, depending on the size and appearance frequency of the motion vector in GOP units. Then, the compression rate table 206 outputs the compression rate to the motion vector comparison unit 202 based on an instruction from the motion vector comparison unit 202.

  The motion vector comparison unit 202 receives the MPEG2 video stream from the first TS decoding unit 201, calculates a motion vector in the MPEG2 video stream, and defines the motion vector, the motion vector, and the compression rate in advance by statistical processing. A comparison is made with the values in the compression rate table 206, and the compression rate for each compression method is output to the sequence header generation unit 204.

  The second TS decoding unit 203 receives the 103-channel CATV TS signal from the BS digital transmitter unit 111, performs TS decoding processing, outputs the MPEG2 video stream to the sequence header generation unit 204, and outputs the MPEG2 audio stream and The other MPEG2 auxiliary information stream is output to the TS encoding unit 205.

  The sequence header generation unit 204 inputs the compression rate for each compression method compared and detected from the 103 channel MPEG2 video stream from the motion vector comparison unit 202 and the 103 channel CATV MPEG2 video stream from the second TS decoding unit 203. Then, the CATV MPEG2 video stream to which the compression rate is added is output to the TS encoding unit 205.

  The TS encoding unit 205 inputs the MPEG2 audio stream and the other MPEG2 auxiliary information stream from the second TS decoding unit 203, and also inputs the CATV MPEG2 video stream to which the compression rate is added from the sequence header generation unit 204. The TS encoding process is performed, and the result is output to the 64QAM modulation unit 207.

  The 64QAM modulation unit 207 receives the 103-channel CATV TS signal from the TS encoding unit 205, performs modulation processing on the 64QAM signal and frequency multiplexing processing with other channel signals, and outputs the result to the transmission line 150.

  FIG. 3 is a schematic diagram showing a state in which the compression rate data in Embodiment 1 of the present invention is added to the MPEG2 video stream.

  Here, the MPEG2 video stream 300 will be described as an MPEG2 video stream for CATV of BS digital broadcasting 103 channels.

  The MPEG2 video stream 300 has a stream structure in which a sequence header and GOP data are arranged on the time axis. The sequence header and GOP data at time T (n) are sequence header T (n) 301, GOP T (n) 302, the sequence header and GOP data at time T (n + 1) are sequence header T (n + 1) 303, and GOP T ( n + 1) 304. In each sequence header, a user data start code and a compression rate for each compression method as user data are added as a user data first compression rate and a user data second compression rate. For example, the sequence header T (n) 301 includes a user data start code 310, a compression rate for each compression method as user data, a user data first compression rate T (n-1) 311 and user data second. A compression rate T (n−1) 312 is added. The sequence header T (n + 1) 303 includes a user data start code 320, a user data first compression rate T (n) 321 and user data second. A compression rate T (n) 322 is added.

  The GOP T (n) 302 at time T (n) is compared by the motion vector comparison unit 202 with the motion vector from the MPEG2 video stream in units of GOPs, and the compression rate for each compression method is output to the sequence header generation unit 204 At this point, the sequence header T (n + 1) 303 at time T (n + 1) is input from the second TS decoding unit 203 to the sequence header generation unit 204. In the sequence header generation unit 204, as user data following the user data start code 320 of the sequence header T (n + 1) 303 of time T (n + 1), user data first compression rate T (n) 321 of time T (n) and The user data second compression rate T (n) 322 is added. As described above, since the compression rate is determined after processing the video data in GOP units, the sequence header generation unit 204 temporally corresponds to the video data before 1 GOP in terms of the compression rate added as user data. Become.

  Therefore, the user data first compression rate T (n−1) 311 and the user data second compression rate T (n−1) 312 are added to the sequence header T (n) 301 of the GOP T (n) 302. Is done. Although GOP T (n−1) is not shown, it indicates video data one GOP before in time.

  In this embodiment, the first compression method is MPEG2, and the second compression method is H.264. H.264 system.

  By repeating the above processing for each GOP, processing for adding a compression rate can be performed for 103 channels of the BS digital signal.

  The compression rate detection / addition unit 120 performs the processing block 200 for each channel as described above on all digital broadcast channels and outputs the result to the transmission path 150.

  Next, processing of the digital CATV receiving apparatus 400 will be described.

  First, a normal viewing process for viewing a desired program according to a user instruction will be described. The 64QAM signal is input from the transmission line 150, the frequency corresponding to the desired program is selected by the channel selection unit 401, the 64QAM signal is demodulated, and the TS signal is output to the TS decoding unit 402. The TS decoding unit 402 decodes the TS signal and outputs an MPEG2 video stream, an MPEG2 audio stream, and auxiliary information to the MPEG2 decoding unit 403. The MPEG2 decoding unit 403 decodes the video and audio and the auxiliary information and outputs the decoded information to the display device 450 so that a desired program can be viewed.

  Next, a description will be given of the same temporary recording / playback processing as that of a conventional digital CATV receiving apparatus for time-shift viewing a desired program according to a user instruction. A channel selection unit 401 selects a desired program from the transmission path 150, demodulates a 64QAM signal, and temporarily records the broadcast TS in the recording unit 405. By outputting the recorded TS signal from the recording unit 405 to the TS decoding unit 402 after a desired time by the user, so-called chasing playback can be performed.

  Next, a description will be given of a recording process in which a desired program is recorded in a longer time than the recording process of the conventional digital CATV receiving apparatus and does not cause significant image quality degradation according to a user instruction.

  The channel selection unit 401 selects a desired program, demodulates the 64QAM signal, temporarily records it in the recording unit 405, and outputs it to the TS decoding unit 402. The TS decoding unit 402 outputs the MPEG2 video stream to the compression rate separation unit 404. The compression rate separation unit 404 detects the sequence header 301 from the MPEG2 video stream, and subsequently detects the user data start code 310. From the user data first compression rate 311 to the video signal added by the digital CATV transmission device 100 A compression rate that does not cause significant image quality degradation is extracted and output to the MPEG2 encoding unit 406. As described in the compression rate addition processing of the digital CATV transmission apparatus, the compression rate added to the sequence header 301 is temporally the compression rate for GOP T (n−1) of T (n−1). . For this reason, in order to absorb the time difference of 1 GOP, it is temporarily recorded in the recording unit 405.

  A broadcast TS signal corresponding to GOP T (n−1) temporarily recorded by the recording unit 405 is output, a video signal is decoded using the TS decoding unit 402 and the MPEG2 decoding unit 403, and input to the MPEG2 encoding unit 406. .

  The MPEG2 encoding unit 406 performs MPEG2 encoding at a compression rate in accordance with the user data first compression rate T (n−1) 311, and the TS encoding unit 407 performs encoding into the recording TS. Output to 405. By repeating the above process until the end of the program, MPEG2 encoding is performed using a compression rate that does not cause noticeable image quality degradation in the video signal obtained by the GOP unit added by the digital CATV transmission apparatus, so that the broadcast TS Compared to recording as it is, a digital CATV system capable of recording for a long time can be realized.

  According to this configuration, the digital CATV transmission device 100 adds a compression rate that does not cause significant image degradation to the video signal of the digital broadcast signal by the compression rate detection / addition unit 120 for each video signal, and sends it out. 400, after selecting and decoding from the input 64QAM signal, the compression rate separation unit 404 separates the compression rate and performs compression processing according to the compression rate separated by the compression unit, so that the optimum compression rate for each video signal It becomes possible to perform compression in the above manner, and recording for a longer time than before can be performed without causing significant image quality degradation.

  In the present embodiment, the recording unit 405 is provided as the digital CATV receiving apparatus 400, but may be an external recording apparatus of the digital CATV receiving apparatus 400. In that case, the digital CATV receiving apparatus 400 includes an interface unit with an external recording apparatus, and the digital CATV receiving apparatus 400 controls the external recording apparatus via the interface unit.

  In the present embodiment, the processing unit for compression rate detection is GOP, but it is also possible to use a picture unit as another processing unit.

(Embodiment 2)
FIG. 4 is a configuration diagram of a digital CATV receiving apparatus according to Embodiment 2 of the present invention.

  The digital CATV receiving apparatus 500 includes a channel selection unit 501, a TS decoding unit 502, an MPEG2 decoding unit 503, a compression rate separation unit 504, H.264 encoding unit 506, TS encoding unit 507, and H.264 encoding unit. An H.264 decoding unit 508, a switching unit 509, and an interface unit 510 are included.

  The channel selection unit 501 receives a 64QAM signal from the transmission line 150, selects a frequency at which a desired program exists, demodulates the 64QAM signal, and outputs the TS signal to the TS decoding unit 502 and the interface 510.

  The TS decoding unit 502 receives an MPEG2 TS signal from the channel selection unit 501, an MPEG2 TS signal from the interface unit 510, or an H.264 signal. H.264 TS signal is input and the TS signal is decoded. In the case of an MPEG2 signal, the H.264 TS signal is sent to the MPEG2 decoding unit 503. H.264 signal is H.264. Each video stream and audio stream are output to the H.264 decoding unit 508, and the MPEG2 TS signal input from the channel selection unit 501 is subjected to TS decoding processing, and the MPEG2 video stream is output to the compression rate separation unit 504.

  The MPEG2 decoding unit 503 receives the MPEG2 video stream and the MPEG2 audio stream from the TS decoding unit 502, performs MPEG2 decoding processing, and outputs the video signal and audio signal to the switching unit 509.

  H. The H.264 encoding unit 506 receives the video and audio signals from the MPEG2 decoding unit 503 and the H.264 from the compression rate separation unit 504. The second compression rate of user data corresponding to the H.264 compression method is input, and the H.264 compression format is set according to the second compression rate. The data is compressed by the H.264 compression method and output to the TS encoding unit 507.

  H. The H.264 decoding unit 508 receives the H.264 decoding from the TS decoding unit 502. H.264-encoded video stream and audio stream are input. The H.264 decoding process is performed, and the video signal and the audio signal are output to the switching unit 509.

  The switching unit 509 is connected to the video signal, audio signal, and H.264 output from the MPEG2 decoding unit 503. The video signal and the audio signal output from the H.264 decoding unit 508 are switched and output to the display device 450.

  The TS encoding unit 507 is an H.264 encoding unit. The video stream and the audio stream are input from the H.264 encoding unit 506, and the H.264 encoding unit 506 is input. H.264 TS is encoded and output to the interface 510.

  The recording apparatus 600 is connected to the digital CATV receiving apparatus 500 via an interface 510 and is connected to an MPEG2 TS signal or H.264. H.264 TS signal is input / output.

  Next, the processing of the second embodiment will be described with reference to FIG.

  The digital CATV receiving apparatus 500 includes an interface 510 for connecting the recording apparatus 600 to the outside, and the recording apparatus 600 is configured to be connected to the outside.

  The processing for adding a compression rate by the digital CATV transmission device 100 of FIG. 1, the processing for directly viewing video data and audio data received by the digital CATV receiving device 500, and the conventional recording processing are the same as in the first embodiment. .

  A recording process in which the recording time is longer than that of the conventional recording process in the recording apparatus 600 by a user instruction and the image quality does not significantly deteriorate will be described in detail because it differs from the first embodiment.

  A channel selection unit 501 selects a frequency corresponding to a desired program, demodulates a 64QAM signal, and outputs an MPEG2 TS signal to the TS decoding unit 502 and the interface 510. Then, the MPEG2TS signal via the interface 510 is temporarily recorded in the external recording device 600.

  The TS decoding unit 502 decodes the MPEG2 TS signal input from the channel selection unit 501 and outputs an MPEG2 video stream to the compression rate separation unit 504.

  The compression rate separation unit 504 detects the sequence header T (n) 301 from the video stream, subsequently detects the user data start code 310, and continues to the user data first compression rate T (n-1) 311. The data second compression rate T (n−1) 312 is separated. The output to the H.264 encoding unit 506. This compression rate is the compression rate for T (n-1) GOP in terms of time, as in the first embodiment.

  A TS signal corresponding to T (n−1) is output from the signal temporarily recorded by the recording apparatus 600, and the video signal is decoded using the interface 510, the TS decoding unit 502, and the MPEG2 decoding unit 503. The output to the H.264 encoding unit 506. H. In the H.264 encoding unit 506, H.264 encoding is performed at a compression rate in accordance with the user data second compression rate T (n-1) 312. The H.264 encoding is performed, the TS encoding unit 507 performs encoding into the recording TS, and outputs to the external recording device 600 via the interface 510.

  By repeating the above-described processing until the program ends, a compression rate that does not cause significant image quality degradation in the video signal obtained by the GOP unit added by the digital CATV transmission device is used. By performing H.264 encoding, it is possible to realize a digital CATV system capable of recording for a long time compared to recording a broadcast TS as it is.

  Next, according to a user instruction, H. A process for reproducing a program recorded in the H.264 format will be described.

  A desired recorded program is selected, and the TS decoding unit 502, H.264, and the like are transmitted from the external recording device 600 via the interface 510. H.264 decoding unit 508 decodes the video signal and the audio signal, and switching unit 509 converts the input signal to H.264. By switching to the output side of the H.264 decoding unit 508 and outputting to the display device 450, the recorded program can be viewed.

  According to such a configuration, the digital CATV receiving apparatus performs channel selection and decoding processing from the input 64QAM signal, then separates the compression rate by the compression rate separation unit 504, and performs compression processing according to the compression rate separated by the compression unit, It is possible to perform compression at an optimal compression rate for each video signal, and recording for a longer time than before can be performed without causing significant image quality degradation.

  In this embodiment, the recording unit is provided outside the digital CATV receiving device as the recording device 600. However, the recording unit is provided inside the digital CATV receiving device, and the recording device is provided outside via the interface 510. It is good also as a form to expand.

  In the present embodiment, the processing unit for compression rate detection is GOP, but it is also possible to use a picture unit as another processing unit.

  Further, in this embodiment, a compression method different from the broadcast method is used in H.264. Although the H.264 compression method is used, the same effect can be obtained by using the VC1 compression method which is another compression method.

  The digital CATV system of the present invention is useful as a system for recording and reproducing programs in a digital CATV system which is modulated and transmitted.

Configuration diagram of a digital CATV system in Embodiment 1 of the present invention The block diagram of the compression rate detection addition part in Embodiment 1 of this invention The schematic diagram showing a mode that compression rate data in Embodiment 1 of this invention was added to the MPEG2 video stream Configuration diagram of digital CATV receiving apparatus according to Embodiment 2 of the present invention Configuration diagram of a digital CATV system in a conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Digital CATV transmitting apparatus 101 BS digital receiving part 102 CS digital receiving part 103 Terrestrial digital receiving part 111 BS digital transmitter part 112 CATV Remux part 113 Terrestrial digital transmitter part 120 Compression rate detection addition part 150 Transmission path 200 Compression rate detection of a channel unit Addition unit 201 First TS decoding unit 202 Motion vector comparison unit 203 Second TS decoding unit 204 Sequence header generation unit 205 TS encoding unit 206 Compression rate table 207 64QAM modulation unit 300 MPEG2 video stream 301 Sequence header T (n)
302 GOP T (n)
303 Sequence header T (n + 1)
304 GOP T (n + 1)
310 User data start code 311 User data first compression rate T (n-1)
312 User data second compression rate T (n-1)
321 User data first compression rate T (n)
322 User data second compression rate T (n)
400 digital CATV receiver 401 channel selection unit 402 TS decoding unit 403 MPEG2 decoding unit 404 compression rate separation unit 405 recording unit 406 MPEG2 encoding unit 407 TS encoding unit 450 display device 500 digital CATV receiving unit 501 channel selection unit 502 TS decoding unit 503 MPEG2 decoding unit 504 compression rate separation unit 506 H.264 encoding unit 507 TS encoding unit 508 H.264 decoding unit 509 switching unit 510 interface 600 recording device

Claims (8)

A digital broadcast receiving unit that receives a digital broadcast signal, a modulation conversion unit that modulates and converts the digital broadcast signal input from the digital broadcast receiving unit, and a significant image quality degradation in the digital broadcast signal input from the digital broadcast receiving unit CATV transmission comprising a compression rate detection adding unit that detects a compression rate that does not cause the compression, and adds the compression rate to the digital CATV signal after modulation conversion that is input from the modulation conversion unit and transmits the compression rate information Equipment,
A compression rate separation unit that inputs the digital CATV signal with the compression rate added thereto and separates the compression rate, a first compression method decoding unit that decodes the digital CATV signal, and the first compression method using the compression rate. A digital CATV receiving device comprising a first compression method encoding unit for compressing a signal decoded by a compression method, and a recording unit for recording the compressed first compression method code signal;
A digital CATV system. A digital broadcast receiver that receives a digital broadcast signal, a modulation converter that modulates and converts the digital broadcast signal, and a compression rate that does not cause significant image quality degradation in the digital broadcast signal input from the digital broadcast receiver. A digital CATV transmission apparatus comprising a compression rate detection adding unit that adds the compression rate to a digital CATV signal after modulation conversion, which is input from the modulation conversion unit, with the compression rate information. The compression rate detection / addition unit includes a TS decoding unit that decodes the digital broadcast signal input from the digital broadcast reception unit, a compression rate table that holds a compression rate according to the magnitude and appearance frequency of a motion vector in GOP units, and A motion vector comparison unit that calculates a motion vector of the decoded signal input from the TS decoding unit and detects a compression rate corresponding to the motion vector from the compression rate table; and the compression rate is converted into a sequence of the digital CATV signal. The digital CATV transmission apparatus according to claim 2, further comprising a sequence header generation unit added to the header. The compression rate detection / addition unit adds a first compression rate based on the same first compression method as that of the digital CATV signal and a second compression rate based on a second compression method. 4. The digital CATV transmission device according to any one of 3. A compression rate separation unit that inputs a digital CATV signal to which a compression rate is added and separates the compression rate, a first compression scheme decoding unit that decodes the digital CATV signal, and the first compression using the compression rate A digital CATV receiving apparatus comprising: a first compression method encoding unit that compresses a signal decoded by a method; and a recording unit that records the compressed first compression method code signal. 6. The digital CATV receiving apparatus according to claim 5, wherein a GOP time is adjusted using the compression rate separated by the compression rate separation unit to the digital CATV signal temporarily recorded in the recording unit. 6. The digital CATV receiving apparatus according to claim 5, further comprising a second compression method encoding unit different from the digital digital CATV broadcast signal. 8. An interface unit for recording the compressed first compression method code signal or the compressed second compression method code signal in an external recording device. The described CATV receiver.

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