JP4293547B2 - Signal recording apparatus and signal recording method - Google Patents

Description

  The present invention relates to a signal recording apparatus and a signal recording method, and more particularly to a signal recording apparatus and a signal recording method capable of simultaneously recording and reproducing a number of television broadcast programs while maintaining a radio wave format. .

  FIG. 12 is a block diagram showing a configuration of a conventional digital terrestrial broadcast receiver and a content recording / playback system. The receiver receives radio waves with an antenna and converts a signal of a desired channel into a low frequency band signal. Since this signal is orthogonal frequency multiplexing (OFDM) modulated in the case of terrestrial digital broadcasting, it is demodulated and returned to a signal (baseband signal) encoded by MPEG2. Further, the encoded signal is decoded (decoded), converted back to an analog signal such as video or audio, and a television program (content) is viewed.

  There are roughly two methods for recording and reproducing contents. The first method is recording on a conventional magnetic tape. This records the decoded video and audio analog signals as analog signals. There is also a method in which the same analog signal is digitized and recorded on a DVD or a hard disk device (hereinafter also referred to as HDD). The second method is a method in which OFDM is demodulated, but the digital signal encoded in MPEG-2 is digitally recorded on, for example, an HDD or a magnetic tape via an IEEE1394 bus. In terms of image quality, the second method is most excellent for digital broadcast program recording.

For example, in the following document, there is an apparatus relating to a first method in which an analog television signal output from a tuner is digitized by a signal processing circuit, further compressed to MPEG image data by a compression / decompression circuit, and then recorded on a hard disk. It is disclosed.
JP 2003-174613 A

  The above-described conventional recording / playback method is suitable for the purpose of recording a desired program and editing the recorded data to create a desired video library for long-term storage. On the other hand, when it is desired to watch or record a program that has been aired in the past about one day and missed, it is required that recordings remain continuously for all broadcast channels for a certain period of time in the past.

  However, the conventional recording / reproducing system does not have such a function. Although it is possible in principle to add such a function to each recording / reproducing apparatus shown in FIG. 12, the configuration of the apparatus becomes complicated, and the circuit and apparatus scale become very large. There was a problem.

  In addition, since the conventional recording / reproducing apparatus is a system for recording / reproducing received / demodulated content, even if there is a defective part of video or audio, there is no function to repair it. There was also.

  An object of the present invention is to provide a digital broadcast wave signal recording apparatus and signal recording method capable of solving the above-described problems and recording and reproducing a number of television programs simultaneously while maintaining the radio wave format. .

  The signal recording apparatus according to the present invention includes a frequency converting means for converting a broadcast signal into a low frequency signal, an A / D converting means for A / D converting the low frequency converted broadcast signal, and an A / D conversion. And a data storage means for storing the processed data.

  In the above signal recording apparatus, the D / A conversion means for D / A converting the data read from the data storage means, and the output signal of the D / A conversion means is converted to a desired frequency. A frequency conversion means may be provided.

  Further, in the signal recording apparatus described above, the frequency converting means may synthesize a plurality of broadcast signals by converting the frequencies into different frequency bands that do not overlap each other.

  The signal recording apparatus described above may further include clock means for outputting time information and time information insertion means for inserting time information output from the clock means into A / D converted data. .

  The signal recording apparatus described above may further include a signal correction unit that reads data from the data storage unit, corrects the signal, and writes the signal in the data storage unit.

  The signal recording method of the present invention stores a step of frequency-converting a broadcast signal into a low-frequency signal, a step of A / D-converting the broadcast signal frequency-converted to a low frequency, and A / D-converted data. The main feature is to include steps.

  According to the present invention, broadcast signals of a plurality of channels can be collectively recorded with a very simple circuit configuration due to the above-described features. And since the entire contents of TV programs for a certain period in the past are recorded, it is possible to easily watch programs that have been overlooked by the same operation as when viewing in real time, greatly improving the convenience of the recording and playback device. This has the effect of improving.

  In addition, when you want to edit and leave a program using a commercially available recording / playback device, the program material is recorded in a form that can be played back multiple times. There is also an effect that the editing operation of the content is remarkably facilitated.

  In addition, since the recorded broadcast signal can be recorded again after being processed, for example, by waveform equalization, there is a possibility that a signal with better image quality can be reproduced in real time than when viewed on a television receiver. There is also an effect that there is.

  FIG. 1 is a functional block diagram showing functions of the signal recording apparatus of the present invention. The distribution means 20 distributes the signal from the antenna 10 into two. The distribution means 20 is not an essential component, and the antenna 10 may be directly connected to the frequency conversion multiplexing means 21.

  The frequency conversion multiplexing means 21 frequency-converts the signal of a desired television broadcast channel into a low-frequency signal, details of which will be described later. A plurality of broadcast signals may be frequency-converted into different frequency bands and synthesized. In this case, packing is performed so that no extra space is generated from the lower frequency (0 Hz), and the upper limit of the entire frequency band is reduced as much as possible.

  The A / D conversion means 22 performs known analog / digital conversion. The input signal is A / D converted through a low-pass filter that passes only a band of 1/2 or less of the sampling frequency fs.

  The time information insertion unit 23 inserts the time information output from the clock unit 29 into data to be recorded at a predetermined period of about 1 second to 1 minute, for example. The time information to be inserted may be time information or elapsed time information from the start of recording. The time information inserting means 23 is not essential constituent elements of the present invention, and the output data of the A / D converting means 22 may be recorded as it is.

  As the data storage means 24, the type of media is arbitrary such as a magnetic disk, an optical disk, a magnetic tape, a semiconductor memory, etc., but preferably has a large capacity. For example, an HDD can be used, for example. The D / A conversion means 25 performs known digital / analog conversion. The frequency conversion means 26 frequency-converts a low-frequency analog signal to a desired broadcast frequency that can be received by the television receiver 12, as will be described in detail later.

  The synthesizing unit 27 synthesizes and outputs the output signal of the frequency conversion unit 26 and the output signal of the distributing unit 20. The synthesizing means 27 is not an essential component of the present invention, and the output of the direct frequency conversion means 26 may be directly connected to the television receiver 12.

  The clock means 29 provides time information to the control means 28. The control means 28 controls each means in the apparatus by, for example, storage program control, and executes recording, reproduction, or signal correction operations. As will be described later in detail, the signal correction unit 30 reads out data stored in the data storage unit 24, performs signal processing such as spectrum equalization processing, and records the data again.

  It is possible to copy the recording data stored in the data storage means 24. Furthermore, it is possible to perform channel selection (digital filter processing), OFDM demodulation, MPEG-2 decoding, etc. by digital processing without D / A conversion of the recorded data. Since these processes do not need to be executed in real time, they can be executed by a low-speed CPU. The recording data amount can be reduced by converting only the necessary program data into MPEG-2 data after recording and recording again. Examples will be described below.

  FIG. 2 is a block diagram showing a hardware configuration example of an embodiment of the signal recording apparatus of the present invention. As an example, an apparatus for recording and reproducing a broadcast signal of terrestrial digital television broadcasting will be described as an example. However, the apparatus and method of the present invention can be used for any broadcast regardless of the modulation method, content, transmission band, etc. / Applicable to recording / reproduction of communication / reproduction signals. A known distribution circuit 40 distributes the signal from the antenna 10 into two. The frequency conversion multiplexing means 41 converts the frequency of a desired television broadcast channel signal into a low-frequency signal.

  FIG. 3 is a block diagram illustrating a configuration example of the frequency conversion multiplexing circuit 41. The distributor 60 amplifies the output signal of the distribution circuit 40 to a predetermined level if necessary, and then distributes it to a plurality of band-pass filters (hereinafter referred to as BPF) 61. The plurality of BPFs 61 are composed of, for example, SAW filters, and each passes only the broadcast signal band of, for example, one of the terrestrial digital broadcast channels.

  The switch circuit 62 is configured by an electronic switching element or the like, and connects an arbitrary BPF 61 and an arbitrary one of the frequency conversion circuits 63 based on an external control signal. In FIG. 3, BPFs 61 corresponding to channels A, C, and E are connected to the frequency conversion circuit 63, respectively.

  The plurality of frequency conversion circuits 63 multiplies the output signal of the BPF 61 and the local oscillation signal output from the local oscillation signal generation circuit 65, and outputs a frequency difference signal. As the frequency conversion circuit 63, for example, a known arbitrary frequency conversion circuit such as a ring modulator can be adopted.

  The local oscillation signal generating circuit 65 is composed of a frequency synthesizer circuit using a known PLL circuit, for example, and generates a plurality of desired local oscillation signals fLO based on control from the outside. The combining circuit is composed of, for example, a resistance adding circuit, and adds and combines the output signals from the plurality of frequency conversion circuits 63.

  In the present invention, it is also possible to adopt a normal superheterodyne system. However, in the normal superheterodyne, since it is converted into an intermediate frequency band having a frequency much higher than the signal bandwidth, separation from the image signal is easy, but in the present invention, the (intermediate) frequency after frequency conversion is the signal band. Since the width is smaller than the width, unless the unnecessary wave is attenuated by the BPF 61 in the previous stage of the frequency conversion circuit 63, the converted signal of 0 Hz or less is turned back to cause interference and cannot be normally received.

  FIG. 5 is an explanatory diagram showing frequency multiplexing of the reception channel to the low frequency band. In this example, three channels A, C, and E are recorded simultaneously. Of the television signals of each channel arranged on the frequency axis, the BPF (in this case, BPF-A, BPF-C, BPF-E) corresponding to the desired channel is passed, and the frequency conversion circuit 63 converts the frequency into a low frequency band. To do.

The difference between the frequency f _LO of the local oscillator signal with the center frequency of a desired channel to control the frequency f _LO of the local oscillator signal entering the frequency converting circuit 63 so that f _1, f _2, f ₃ in FIG. The arrangement on the frequency axis in the low frequency band is densely arranged in such a range that does not affect each other from the lower frequency. In a terrestrial digital broadcasting system having a channel frequency interval of 6 MHz, for example, it may be arranged at an interval of 6.5 MHz. In this way, the total bandwidth W is about 20 MHz for the three channels.

  FIG. 6 is an explanatory diagram showing an example in which a plurality of channels having continuous broadcast frequencies are recorded together. In the case of terrestrial digital broadcasting, a plurality of broadcasting channels are densely arranged without gaps. In this case, as shown in FIG. 6, the BPF (AD) 61 that allows only the entire plurality of broadcast channels to pass through is used, and the frequency of the output signal is converted, thereby simplifying the circuit configuration of the recording apparatus. It becomes. In this case, since frequency conversion can be performed by one frequency conversion circuit 63, only one BPF 61, frequency conversion circuit 63, and local oscillation signal generation circuit are required, and a distribution circuit, a switch circuit, a synthesis circuit, and the like are unnecessary. It becomes.

  The capacity of the HDD at the present time is about several hundred GB, but this value increases with the times, and the capacity of the HDD can be expected to be several TB in a few years ahead. With the latter performance, as shown in FIG. 6, it is possible to record for a long time by taking out a single BPF having a band of all the signals of several channels and performing frequency conversion in a lump.

  Returning to FIG. 2, the A / D conversion circuit 42 performs sampling at a sampling frequency fs that is twice (2 W) or more of the signal band W that satisfies the sampling theorem, and converts the analog signal into a digital signal. The A / D converter requires a sampling frequency of about several tens to several hundreds of MHz and a conversion accuracy of about 8 to 12 bits. Such an A / D converter is commercially available. The input signal is A / D converted through a low-pass filter that passes only a band of 1/2 or less of the sampling frequency fs.

  The ADC interface (I / F) circuit 54 executes data input from the A / D conversion circuit 42 and data output to the D / A conversion circuit 43 under the control of the CPU. The control interface circuit 55 controls the frequency conversion multiplexing circuit 41, the A / D conversion circuit 42, the D / A conversion circuit 43, and the on-frequency conversion circuit 44 based on the control of the CPU.

  The CPU, the ROM, and the RAM 50 correspond to the control unit 28, and the CPU controls the entire recording apparatus by executing a program for processing to be described later stored in the ROM.

  The hard disk device 51 preferably has a large capacity. For example, when the band of the broadcast signal is 6 MHz, if the sampling frequency fs of the A / D converter is 15 MHz and the accuracy is 8 bits (1 byte), data of 15 MB per second is generated. Therefore, for example, in order to record this signal for 3 hours × 4 channels per day, 15 MB × 3600 × 3 × 4 = 648 GB is sufficient, which can be realized by using several currently available HDDs. Note that by using the data compression technique, it is possible to reduce the amount of stored data and extend the recording time.

  The panel / remote control circuit 52 includes a liquid crystal display device, a switch, a keyboard, a remote control signal transmission / reception circuit, and the like, and inputs operation information of the user and displays the status and message of the device. The clock circuit 53 incorporates a crystal oscillator or the like and provides time information. The D / A conversion circuit 43 performs known digital / analog conversion.

  FIG. 4 is a block diagram illustrating a configuration example of the on-frequency conversion circuit 44. The frequency conversion circuit 44 converts the low-frequency analog signal to a desired broadcast frequency that can be received by the television receiver 12. As the frequency conversion circuit 67 and the local oscillation signal generation circuit 68, the same circuit as the frequency conversion circuit 63 and the local oscillation signal generation circuit 65 of FIG. 3 can be used. The synthesizing circuit 45 synthesizes and outputs the output signal of the frequency conversion circuit 44 and the output signal of the distribution circuit 40.

FIG. 7 is an explanatory diagram showing frequency conversion for extracting a desired channel signal during reproduction. It is assumed that channels A, B, and C are recorded as one data, and that a program on channel B is to be reproduced. Information indicating which channel is recorded in which frequency band is stored in recorded data or as a separate file. Also, it is assumed that the television receiver is set so that it can be viewed with an empty channel x (the center frequency is f _R ).

In this case, when the reproduction of channel B is designated, the frequency f _LO of the local oscillation signal becomes f _R −f ₂ . Thereby, the program of channel B can be viewed on channel x of the television. Thus, the channel setting can be dealt with by changing the transmission frequency of the local oscillation signal. If the upper and lower channels of channel x are also free in the state of FIG. 7, for example, channel A or channel C can be viewed by changing the television channel up and down.

  Also, as shown in FIG. 6, when a plurality of channels are recorded in a lump, instead of designating the reproduction of a specific channel, the plurality of channels are converted to the original broadcast frequency band, thereby It is possible to select and view a desired channel in the same manner as viewing in real time. In this case, a switch circuit is used instead of the synthesis circuit 45 so that only the output signal of the frequency conversion circuit 44 is input to the television receiver 12.

  FIG. 8 is an explanatory diagram showing addition of time information (time code) to A / D conversion data. For reproduction, a mechanism for instantaneously extracting data of a desired channel and a designated time is required. Therefore, the time information is recorded in the header of the sectorized data, and this is searched to realize the reproduction start from an arbitrary time.

  The A / D converted signal 70 is blocked at an appropriate time interval, and a time code 73 as time information is added to each signal data block 72 as header information. This is continuously recorded on the HDD as a sector. The unit time for blocking may be, for example, about 1 second to 1 minute. . At the time of reproduction, this time information is D / A converted from the removed digital data 74.

For the channel information, the center frequency (f ₁ , f ₂ , f _{3 in} FIG. 5) of each channel signal after being converted to the low frequency band, or the order information on the frequency axis, together with the time code or separately. Record it. Thereby, it is possible to specify a channel at the time of reproduction.

  FIG. 11 is a flowchart showing the contents of recording and reproduction processing of the signal recording apparatus of the present invention. In the signal recording device, it is assumed that information on a time zone for recording daily and a channel for recording is set in advance. In the recording process of FIG. 11A, in S10, the process waits until the recording start time comes. In S11, a channel is selected. That is, the BPF 61 corresponding to the channel to be recorded is connected to the frequency conversion circuit 63, and the local oscillation signal frequency data is set in the local oscillation signal generation circuit 65.

  In S12, the date / time information and the arrangement information of the channel to be recorded are generated and written in the header information added to the data or stored as a separate file. In S13, recording start control is performed. That is, the A / D converter is set to perform A / D conversion at a predetermined sampling period, the converted data is read into the RAM, and when the data for a predetermined time is accumulated, a time code is added and written to the HDD Set to repeat.

  In S14, it is determined whether or not a predetermined time has elapsed. If the determination result is negative, the process proceeds to S16, but if the determination is affirmative, the process proceeds to S15. In S15, for example, time information is acquired from the clock circuit, and a time code including the time information is inserted into the recording data. In S16, it is determined whether or not the end time is reached. If the determination result is negative, the process proceeds to S14, but if the determination is affirmative, the process proceeds to S17. In S17, recording end control is performed.

  In the playback process of FIG. 11B, in S20, the playback time zone and channel desired by the user are input based on the playback operation of the user using the panel or the remote control. In S21, channel setting is performed. That is, the frequency conversion circuit 44 is set so that the recorded signal of the desired channel is converted into the frequency of the desired channel of the television receiver.

  In S22, playback is started from the designated date and time. That is, the time code in the recorded data is searched, the reading from the sector data corresponding to the desired reproduction start time is started, and the D / A conversion circuit 43 is set so as to perform D / A conversion every predetermined sampling period. Control. In S23, the reproduction process is continued until a predetermined time has elapsed, and in S24, a reproduction end process is performed.

  Next, correction of the recorded signal will be described. According to the recording apparatus of the present invention, when the quality of the signal recorded by the recording apparatus is deteriorated due to the poor radio wave environment at the reception point, waveform shaping (equalization) or the like is performed on the signal. Digital signal processing can be performed and processed and reproduced without quality degradation.

  The processing referred to here means, for example, processing on software that performs frequency analysis on the received signal and flattens the frequency characteristics by signal processing. The processing content is arbitrary, such as waveform shaping, extraction of specific channel signals (filtering), OFDM demodulation, decompression of compressed signals or conversion to other compression methods, and since they are recorded on the HDD, the processing is performed in real time. Therefore, it can be executed by a low-speed CPU.

  FIG. 9 is a block diagram showing a waveform shaping process which is an example of the signal correction unit 30. FIG. 10 is an explanatory diagram showing signal quality determination and waveform shaping results by frequency component analysis. The frequency component analysis means (FFT) extracts a part of the recording data, for example, about 1 second before and after the specified time as one block data, and performs frequency component analysis using, for example, fast Fourier transform.

  The waveform distortion determination means 81 determines that the radio wave environment is poor (NG) when the frequency characteristic has a dispersion of a certain range or more due to the influence of a reflected wave or the like, and the radio wave environment is good if the dispersion is within the range. Judge as (OK). FIG. 10A shows an example in which NG is determined. If it is determined to be NG, the waveform shaping means 82 performs a correction operation to weight each frequency component and make it flat. FIG. 10B shows an example of the spectrum after the correction calculation. In the case of NG, the data writing control means 83 replaces the original signal with the data processed by the waveform shaping means 82 and saves it. The method described here is merely an example, and the quality determination method of the recorded signal and the signal processing method in the case of NO are arbitrary.

  Although the embodiments have been described above, the following modifications may be considered for the signal recording apparatus of the present invention. As an embodiment, the configuration example as shown in FIG. 2 is disclosed. For example, the present invention can be achieved by mounting a board having a frequency conversion function, an A / D conversion function, a D / A conversion function, etc. on a known personal computer. It can be implemented. In this case, a signal is recorded on the HDD provided in the personal computer.

  As an embodiment, an apparatus for recording and reproducing a broadcast signal of terrestrial digital television broadcasting has been disclosed. However, the apparatus and method of the present invention can be used for any broadcast / communication / reproduction regardless of the modulation scheme, content, transmission band, etc. The present invention can be applied to signal recording / reproduction. For example, an analog broadcast signal and a digital broadcast signal may be mixed.

  In order to record / reproduce without modifying a normal television receiver, the reproduced signal must be returned to the frequency band of the broadcast wave. However, when the recording / reproducing apparatus of the present invention and the receiver are designed as one unit In this case, the reproduced signal is not returned to the high frequency signal, but can be connected as the input signal of the television receiver with the baseband signal subjected to low frequency or quadrature detection (IQ separation).

In the present invention, since the recorded signal can be processed, by using the recorded received signal and performing processing such as performing predetermined deterioration on the received signal, in a mobile environment where reception deterioration is expected. It can also be used for evaluation of reception characteristics and the like.
As an embodiment, an example in which conversion is performed by one A / D converter has been disclosed. However, a plurality of A / D converters are used, or one A / D converter is time-division-multiplexed to perform a plurality of conversions. The low frequency signals of the channels may be A / D converted and recorded as separate data.

It is a functional block diagram which shows the function of the signal recording apparatus of this invention. It is a block diagram which shows the hardware structural example of the Example of the signal recording apparatus of this invention. 3 is a block diagram illustrating a configuration example of a frequency conversion multiplexing circuit 41. FIG. 3 is a block diagram illustrating a configuration example of an on-frequency conversion circuit 44. FIG. It is explanatory drawing which shows the frequency multiplexing to the low frequency band of a receiving channel. It is explanatory drawing which shows the example which records a several continuous channel collectively. It is explanatory drawing which shows the frequency conversion at the time of reproduction | regeneration. It is explanatory drawing which shows addition of the time information to A / D conversion data. It is a block diagram which shows the waveform shaping process which is an example of a signal correction means. It is explanatory drawing which shows the signal quality determination and waveform shaping result by a frequency component analysis. It is a flowchart which shows the content of the recording and reproduction | regeneration processing. It is a block diagram which shows the structure and recording / reproducing system of the conventional receiver.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Antenna 11 ... Signal recording device 12 ... Television receiver 20 ... Distribution means 21 ... Frequency conversion multiplexing means 22 ... A / D conversion means 23 ... Time information insertion means 24 ... Data storage means 25 ... D / A conversion means 26 ... On-frequency conversion means 27 ... Synthesis means 28 ... Control means 29 ... Clock means 30 ... Signal correction means

Claims (5)

Each frequency band does not overlap and is densely arranged in a range that does not affect each other from the lowest frequency, and by converting multiple broadcast signals to different frequency bands and synthesizing them into low frequency signals A frequency conversion means for frequency conversion;
A / D conversion means for A / D converting a signal frequency-converted to a low frequency by the frequency conversion means;
Data storage means for storing data A / D converted by the A / D conversion means;
D / A conversion means for D / A converting the data read from the data storage means;
A signal recording apparatus comprising: an on-frequency converting means for converting an output signal of the D / A converting means to a desired frequency.   2. The timepiece means for outputting time information, and time information insertion means for inserting time information output from the timepiece means into the A / D converted data. Signal recording device.   2. The signal recording apparatus according to claim 1, further comprising a signal correction unit that reads data from the data storage unit, corrects a signal, and writes the data in the data storage unit.   The signal recording apparatus according to claim 1, wherein the frequency conversion unit includes a plurality of band-pass filters that allow only a plurality of broadcast signals to pass therethrough.   The signal recording apparatus according to claim 1, wherein the frequency conversion unit includes a band-pass filter that collectively passes a plurality of broadcast signals having adjacent frequency bands.

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