JPH089330A - Digital signal processing unit in image transmission system - Google Patents

Abstract

PURPOSE:To allow the processing unit to record and reproduce received multiplexed data simultaneously. CONSTITUTION:Multiplexed data from a local conditional access processing circuit 5 are fed to recording signal processing circuits 12, 16. A digital VTR recording and reproducing section 14 and a HDD recording and reproducing section 18 record simultaneously the received multiplexed data and record a time code or the like together with the multiplexed data. Furthermore, the HDD section 18 records and reproduces the multiplexed data simultaneously and the digital VTR section 14 reproduces the multiplexed data in succession to the multiplexed data reproduced by the HDD section 18. The reproduced multiplexed data are fed to an MPEG decoder circuit 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image transmission system for transmitting a television signal subjected to time base compression, for example, a digital signal processing device in digital CATV or digital satellite broadcasting.

[0002]

2. Description of the Related Art Conventionally, a signal transmitted from a broadcasting station has been an analog video / audio signal. In recent years, with the development of digital technology, the transmission from this broadcasting station is being digitized. Also, due to advances in compression technology,
A video signal transmitted from a broadcasting station is compressed with high efficiency, and, for example, in the conventional analog 1 channel transmission band, about 1
It is becoming possible to transmit 0-channel signals.

Further, a method of transmitting a highly efficient compressed signal on the time axis is also considered. That is, as an example, when a video signal compressed to 1.5 Mbps is transmitted using a transmission line capable of transmitting actual digital data excluding error correction codes at 24 Mbps, for example, it is 16 times on the time axis. It can be compressed to 2 hours and a 2-hour movie can be sent in 7-8 minutes.

Here, FIGS. 6 and 7 show a configuration in which a signal highly compressed is further compressed on the time axis and transmitted. In FIG. 6, a transmission request for a desired program is sent from each home to the program distribution center 101 using a telephone line. In the program distribution center 101, the digital signal which has been highly efficiently compressed and which has been subjected to time-axis compression processing is transmitted via the parabolic antenna 102 to the communication satellite 1
03 is transmitted. The communication satellite 103 transmits the received digital signal to the parabolic antenna 104 of the cable TV center and / or the parabolic antenna 107 of each home. The cable TV center 105 transmits the received digital signal to the contracted home 108 using a CATV line.

By the way, in such a system, since the received digital data is compressed on the time axis, it cannot be viewed as it is. That is, on the receiving side, the received digital data must be recorded in a recording device such as a digital VTR, and after the recording of one broadcast program is completed, the time axis must be restored and reproduced. Therefore, each home 106, 108 has a receiver connected to the recording device, and records the digital signal once received by the recording device. Then, the broadcast program is played back after the recording is completed while returning the time axis to the original position.

Further, for example, the billing information is stored in the billing database (not shown) of the program distribution center via the telephone line when recorded in the recording device, and the viewing fee is paid from each home through the financial institution 109. Be seen.

Next, FIG. 7 shows the internal structure of the program distribution center 101. A signal from a video / audio signal source 110 such as a VTR or an optical disc is sent to the MPEG encoder unit 11
At 1, it is highly efficiently compressed. The compressed signal is packetized by the packet generation unit 112 and compressed on the time axis by the time axis compression processing unit 113. In FIG. 7, the above-described processing system is provided for a plurality of channels, and the signals processed by these channels are sent to the multiplexer 11
In 4, the multiplexing process is performed. The multiplexed signal is encrypted in the scramble processing unit 116 by the scramble key generated in the conditional access unit 115. This scramble key may be transmitted to each home using a telephone line, or may be multiplexed with a transmitted digital signal and transmitted. The encrypted signal is subjected to modulation suitable for addition and transmission of an error correction code via the error processing unit 117 and the modulation unit 118. The signal processed as described above is output to the output terminal 119.
And transmitted via the parabolic antenna 102.

The applicant of the present invention received the digital signal transmitted as described above in Japanese Patent Application No. 5-137651 filed on June 8, 1993, and recorded it using a digital VTR. Then, we applied for a recording and reproducing device that reproduces while returning the time axis to the original. In this case, when the user wants to watch a 2-hour movie at each home, he / she cannot immediately watch it even if he / she makes a request to the broadcasting station, and the data is recorded on a recording device such as a digital VTR. After all the recording is completed, it is necessary to wait at least 7 to 8 minutes before starting to watch the movie, because it is played back by reversing the time axis.

[0009]

Therefore, the present invention is
Provided is a digital signal processing device in an image communication system capable of shortening the time from when a request for an image signal transmitted from a broadcasting station after time-base compression is sent to the broadcasting station to when a movie is actually started. The purpose is to do.

[0010]

SUMMARY OF THE INVENTION The present invention provides a digital signal processing apparatus for recording / reproducing multiplexed data in an image communication system in which time-axis compressed multiplexed data is received. A first recording / reproducing apparatus for recording data, a first partial data of the multiplexed data is recorded in parallel with the recording operation of the first recording / reproducing apparatus, and a partial data is reproduced. After the second recording / reproducing device and the first recording / reproducing device have finished recording the multiplexed data for a predetermined period, the second recording / reproducing device is shifted to the reproducing state, and the partial data reproduced by the second recording / reproducing device is expanded on the time axis. And a control means for continuing the time axis expanded signal reproduced by the first recording / reproducing apparatus for the signal. A signal processing unit.

[0011]

The received time-compressed digital data is continuously recorded in the digital VTR unit for one broadcast program to the end. Simultaneously with the start of recording in the digital VTR section, the HDD section records the time-axis-compressed digital data for a predetermined period. For example H
The recording operation of the DD section is performed until the disc is full. After the recording in the HDD section is completed, the reproduction operation in the HDD section is started. The digital data reproduced from the HDD unit is expanded on the time axis and output as restored image data to, for example, a monitor. When recording is completed to the end in the digital VTR section, the magnetic tape is rewound to the point where reproduction is being performed in the HDD section and switched to reproduction by the digital VTR section. After the switching is performed, the digital VTR section reproduces the broadcast program to the end, thereby receiving the time-axis-compressed digital signal and recording the digital signal in the digital VTR section. When the recording in the HDD section is completed, the broadcast program contents can be viewed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a digital signal processing device according to the present invention will be described below with reference to the drawings.
FIG. 1 shows a block diagram of an example of a digital signal processing device of the present invention. For example, MPEG2 (Moving Picture E
xperts Group 2) high-efficiency-coded and time-axis-compressed digital signals, or digitally-multiplexed data obtained by multiplexing digital signals just high-efficiency-coded by MPEG2 are supplied to the tuner circuit 1. The tuner circuit 1 selectively receives a desired broadcast channel.

After the signal in which the desired broadcast channel is selected by the tuner circuit 1 is demodulated by the demodulation circuit 2, the error correction circuit 3 corrects the error generated in the transmission system. The error-corrected signal is supplied to the demultiplexer circuit 4, and the desired program is selected. The signal output from the demultiplexer circuit 4 is supplied to the local conditional access processing circuit 5 and descrambled in accordance with the contract information stored in the IC card 6. When the scramble is released, the microcomputer 23 transmits the billing information to the program distribution center 101 using the telephone line via the modem 24. The descrambled signal is supplied from the local conditional access processing circuit 5 to the movable contact 7 a of the switch circuit 7. The fixed contact 7b of the switch circuit 7 is connected to the recording / reproducing unit 11, the fixed contact 7c of the switch circuit 7 is connected to the fixed contact 8a of the switch circuit 8, and the fixed contact 8b is recorded / reproduced. A signal from the unit 11 is supplied. The movable contact 8c of the switch circuit 8 has an MPE
It is connected to the G decoder circuit 9. The signal output from the MPEG decoder circuit 9 is output to a monitor or the like via the output terminal 10.

Next, the recording / reproducing section 11 for recording the received digital signal will be described. Recording / playback unit 1
1 is mainly composed of a digital VTR recording / reproducing unit 14 and an HD.
And a D recording / reproducing unit 18. The signal supplied to the fixed contact 7b of the switch circuit 7 is supplied to the recording signal processing circuits 12 and 16. The recording signal processing circuit 12 includes a buffer, an error correction code encoding circuit, a framing circuit, a channel modulation circuit, and the like, and performs each processing. The output of the recording signal processing circuit 12 is supplied to the digital VTR recording / reproducing unit 14 via the switch circuit 13 and recorded on the magnetic tape. Here, on the magnetic tape, in addition to the image signal and the audio signal, the time code data generated by the time code generation circuit 21 and the absolute track number generated by the absolute track number generation circuit 22 are recorded.
For example, it is recorded in the subcode area on the magnetic tape.

When reproducing the recorded magnetic tape, it is supplied to the reproduction signal processing circuit 15 via the switch circuit 13 and to the fixed contact 8b of the switch circuit 8 via the switch circuit 20. The reproduction signal processing circuit 15 includes a channel demodulation circuit, an error correction code decoding circuit, and a TBC.
A circuit, a frame decomposing circuit, etc. are included and each processing is performed.

The signal supplied to the recording signal processing circuit 16 is sent to the HDD recording / reproducing unit 1 via the switch circuit 17.
8 and is recorded on the hard disk. The recording signal processing circuit 16 includes a buffer, an error correction code encoding circuit, a framing circuit, a channel modulation circuit, and the like, like the recording signal processing circuit 12 described above, and performs each processing. Here, the time code data generated by the time code generation circuit 21 is recorded on the hard disk together with the image / sound signal.

The signal reproduced from the hard disk is H
The signal is supplied from the DD recording / reproducing unit 18 to the reproduction signal processing circuit 19 via the switch circuit 17. Reproduction signal processing circuit 19
Includes a channel demodulation circuit, an error correction code decoding circuit, a frame decomposing circuit, and the like, similar to the reproduction signal processing circuit 15 described above, and performs each processing. The output of the reproduction signal processing circuit 19 is supplied to the fixed contact 8b of the switch circuit 8 via the switch circuit 20.

The switch circuits 7, 8, 13, 17, 20,
The switching of 26 is controlled by the microcomputer 23. The microcomputer 23 is connected to an IC card 6, an operation panel 25, a modem 24, and a remote controller light receiving unit 27 that receives control signals from the remote controller 25, and the digital VTR recording / reproducing unit 14 is connected.
It also controls the drive system of the HDD recording / reproducing unit 18.

In FIG. 1, the signal after the local conditional access processing circuit 5 is supplied to the recording / reproducing section 11, but the signal supplied to the local conditional access processing circuit 5, that is, in this embodiment. ,
The signal output from the demultiplexer circuit 4 may be supplied to the recording / reproducing unit 11. However, by disposing the recording / reproducing unit 11 after the local conditional access processing circuit 5, since the descrambled digital signal is recorded, the search can be performed by the visible image.

Now, the operation of FIG. 1 will be described. First, the user selects a desired program service by moving the cursor 30 using the operation panel 25 and / or the remote controller 25 on the program selection screen displayed on the monitor or television as shown in FIG. Then, a case will be described in which the selected program is “1. Free program” or “2. Pay program (viewing)” which is highly efficient coded by MPEG2. In this case, the switch circuit 7 is switched to the fixed contact 7c side and the switch circuit 8 is switched to the fixed contact 8a side so that the signal processing can be performed while the signal processing is performed together with the signal reception, and the signal is decoded by the MPEG decoder circuit 9. Output to the monitor. still,
When "2. Pay program (viewing)" is selected, it is not recorded in the recording / reproducing unit 11, but since it is a pay broadcast, the billing information is sent to the program distribution center 101 via the modem 24. Since this billing information is only the viewing fee for one time, it is relatively cheap.

Next, when the user selects "3. Pay program (record)" on the program selection screen, MPEG2
If a high-efficiency-coded program is recorded in the recording / playback unit 11 and is desired to be viewed at a later date, the switch circuit 7 is switched to the fixed contact 7b side to switch to the digital VTR.
It is recorded in the recording / reproducing unit 14. Only in this case, the program can be viewed even while the switch circuit 26 is turned on and the digital VTR recording / reproducing unit 14 is recording. In this case, since recording is performed in the digital VTR recording / reproducing unit 14 and viewing can be performed any number of times, the charging information sent to the program distribution center 101 via the modem 24 is different from the one-time viewing fee described above. Will be expensive. If a program other than “3. Pay program (record)” is selected on the program selection screen, the switch circuit 26
Is turned off.

Next, in the program selection screen, the user
A case will be described in which the program "4. Pay program (high-speed delivery)" that is highly efficient coded by MPEG2 and that has been time-axis compressed is selected. In this case, since it is impossible to perform the signal processing at the same time as the reception and to watch it, the switch circuit 7 is switched to the fixed contact 7b side so that the recording / reproducing unit 11 once records.

FIG. 3 is a timing chart showing an example of the recording / reproducing operation. FIG. 3 shows an example in which the time axis is compressed to 1/6 and a movie for 2 hours is received. Figure 3A
The time period (20 minutes) during which the time-axis compressed movie is received is shown. FIG. 3B shows a period (about 4 minutes) during which a time-axis-compressed movie is recorded in the HDD recording / reproducing unit 18. Figure 3C
Indicates a period (about 24 minutes) during which the movie recorded in the HDD recording / reproducing unit 18 is reproduced. FIG. 3D shows a digital VTR.
A period (20 minutes) during which a time-axis-compressed movie of 2 hours is recorded in the recording / reproducing unit 14 is shown. FIG. 3E shows the digital V
The period (about 1 to 2 minutes) during which the TR recording / reproducing unit 14 is rewinding and cueing the magnetic tape on which the movie is recorded is shown. FIG. 3F shows a period during which the digital VTR recording / reproducing unit 14 is reproducing the movie recorded on the magnetic tape.

As can be seen from FIGS. 3A, 3B and 3D, the digital VTR recording / reproducing unit 14 and the HDD recording / reproducing unit 18 record the movie at the same time when the reception of the movie subjected to the time base compression is started. Start. At this time, the recording rates of the digital VTR recording / reproducing unit 14 and the HDD recording / reproducing unit 18 are the same. The HDD recording / reproducing unit 18 records data until the hard disk is full (about 4 minutes). When the hard disk is full, playback is started immediately as shown in FIG. 3C. Since the hard disk has a faster access speed than the magnetic tape, the reproduction can be started immediately after the end of recording. When the hard disk is played back, the moving speed of the recording / playback head (not shown) is set slower than the speed at the time of recording to restore the time axis to the original position, or the played signal is temporarily stored in the memory (not shown). , By setting the read clock appropriately, the time axis is restored and reproduced. The signal whose time axis has been returned to its original state is supplied to the MPEG decoder circuit 9 via the switch circuit 20 and the switch circuit 8 (the switch circuit is switched to the fixed contact 8b side) to be restored.

When the movie recorded on the HDD recording / reproducing unit 18 is being reproduced, the digital VTR recording / reproducing unit 14 is operated.
Records the movie to the end on magnetic tape. Digital V
When the recording of the movie is completed in the TR recording / reproducing unit 14,
The microcomputer 23 recognizes the time code of the portion currently being reproduced by the HDD recording / reproducing unit 18 and converts it into the absolute track number recorded on the magnetic tape.
Do. The microcomputer 23 rewinds the magnetic tape at a high speed to the absolute track number of the calculated result, and then performs the cue. Since high-speed search with absolute track numbers is possible up to about 200 times speed, it is possible to rewind to the tape top in about 6 seconds if recording for 20 minutes, so even if the time for cueing is included, It is possible to synchronize with the part where the hard disk is playing in 1 to 2 minutes.

When the HDD recording / reproducing unit 18 is synchronized with the reproducing portion, the switch circuit 20 is switched to switch the reproduction from the digital VTR recording / reproducing unit 14. This allows the viewer to continue watching until the end of the program.

As described above, in the hard disk of the HDD recording / reproducing unit 18, the time (20 minutes) required for the digital VTR recording / reproducing unit 14 to record the program to the end and the recorded magnetic tape are rewound to the hard disk. Time required to synchronize with the part that is playing (about 1-2 minutes)
It suffices to record the data so that it can be reproduced only for the added time, and at the same time, it suffices to have the capacity.

Therefore, the user needs to rewind (about 22 minutes) after the recording of the digital VTR recording / reproducing section 14 is completed.
It is not necessary to wait until the hard disk finishes recording (about 4 minutes). Therefore, the waiting time is greatly shortened.

Next, a second embodiment using the present invention will be described with reference to FIGS. 4 and 5. Although a block diagram is shown in FIG. 4, description of the same components as those in FIG. 1 will be omitted, and only different components will be described. Figure 4
In the HDD recording / reproducing unit 18, a recording-only head (not shown) and a reproduction-only head (not shown) are separately provided. The signal output from the recording signal processing circuit 16 is supplied to the recording-only head and recorded on the hard disk. In addition, since the read-only head is provided in the second embodiment, the recorded portion can be immediately reproduced at the same time as the recording. The reproduced signal is FI
It is input to an FO memory (First In First Out memory) 31, the time axis is returned to the original, and output to the reproduction signal processing circuit 19.

FIG. 5 is a timing chart showing an example of the recording / reproducing operation in the second embodiment. FIG. 5 shows an example in which the time axis is compressed to 1/6 and a movie for 2 hours is received as in the first embodiment. Figure 5A
Is the time period (20
Minutes). FIG. 5B shows a period (about 4 minutes) during which the HDD recording / reproducing unit 18 is recording a time-axis compressed movie. FIG. 5C shows a period (about 24 minutes) during which the movie recorded by the HDD recording / reproducing unit 18 is being reproduced. FIG. 5D shows
The period (20 minutes) during which the digital VTR recording / reproducing unit 14 is recording a time-compressed movie is shown. Figure 5E shows
A period during which the digital VTR recording / reproducing unit 14 is rewinding and cueing the magnetic tape on which a movie is recorded (about 1-2).
Minutes). FIG. 5F shows the digital VTR recording / reproducing unit 14.
Indicates the period during which the movie recorded on the magnetic tape is being reproduced.

In the second embodiment, as can be seen from FIGS. B, C, and D, the digital VTR recording / reproducing section 14 and the HD are simultaneously started when the reception of the program subjected to the time base compression is started.
Both recordings of the D recording / reproducing unit 18 are started, and further, the HDD
The recording / reproducing unit 18 is different from the first embodiment in that the recording / reproducing unit 18 also performs a reproducing operation at the same time. Also in this case, the recording rates of the digital VTR recording / reproducing unit 14 and the HDD recording / reproducing unit 18 are the same. The HDD recording / playback unit 18 records data until the hard disk is full (about 4
Minutes). Therefore, the reproduction data for 24 minutes is recorded in the hard disk when the time axis is restored. Although the reproduced data is stored in the FIFO memory 31 and the time axis is returned to the original position in FIG. 4, the moving speed of the read-only head may be slower than the moving speed of the recording-only head for playback. good.

While the HDD recording / reproducing unit 18 is reproducing, the digital VTR recording / reproducing unit 14 completes recording until the end of the program. When the recording of the digital VTR recording / reproducing unit 14 is completed, the reproducing position of the HDD recording / reproducing unit 18 and the digital VTR recording / reproducing unit 1 are performed as in the first embodiment.
4 is synchronized with the reproduction start point, and after the synchronization is achieved, the switch circuit 2 is provided on the reproduction side of the digital VTR recording / reproducing unit 14.
0 is switched. This allows the viewer to continue watching until the end of the program.

As described above, as in the first embodiment, the hard disk of the HDD recording / reproducing unit 18 has a digital VTR.
The time required for the recording / reproducing unit 14 to record the program to the end (20 minutes) and the time required for rewinding the recorded magnetic tape and synchronizing it with the portion being reproduced by the hard disk (about 1 to 2 minutes ) Need only be recorded so that the program can be played back for an additional time, and at the same time, the hard disk only needs to have a recording capacity.

As described above, in the second embodiment, the HDD recording / reproducing unit 18 simultaneously executes the recording operation and the reproducing operation, so that the user can see the image with almost no waiting.

In the above-mentioned embodiments, the hard disk is used for recording, but the present invention is not limited to this. For example, an optical disk, a magneto-optical disk, a semiconductor or the like can be used.

Further, in the above embodiment, the digital VT
Reproduction start point of R recording / reproducing unit 14 and HDD recording / reproducing unit 1
Although the time code is used to synchronize with the reproduction point of No. 8, the synchronization may be achieved by using the address of the hard disk and calculating the track number or time code of the magnetic tape.

Furthermore, in the above-mentioned second embodiment, H
Although the DD recording / reproducing unit 18 is provided with the recording-only head and the reproduction-only head separately, the present invention is not limited to this, and the recording / reproducing head and the FIFO are used to perform the time-division processing of the recording operation and the reproducing operation. You may do it.

[0038]

Since the digital signal processing device according to the present invention can reproduce the digital image data compressed in the time domain at the same time or in a short time, the waiting time for the user can be short. It is possible to view the restored image data immediately after the user's request.

[Brief description of drawings]

FIG. 1 is a first digital signal processing device according to the present invention.
It is a block diagram showing an example of.

FIG. 2 is a diagram showing an example of a program selection screen according to the present invention.

FIG. 3 shows a first digital signal processing device according to the present invention.
6 is a timing chart showing a recording / reproducing operation in the embodiment of the present invention.

FIG. 4 shows a second digital signal processing device according to the present invention.
It is a block diagram showing an example of.

FIG. 5 shows a second digital signal processing device according to the present invention.
6 is a timing chart showing a recording / reproducing operation in the embodiment of the present invention.

FIG. 6 is a diagram showing an image transmission system for receiving time-axis-compressed digital image data according to the present invention.

FIG. 7 is a block diagram of a transmission side of an image transmission system for receiving time-axis-compressed digital image data according to the present invention.

[Explanation of symbols]

 14 Digital VTR recording / reproducing unit 18 HDD recording / reproducing unit 23 Microcomputer 12, 16 Recording signal processing circuit 15, 19 Reproducing signal processing circuit 7, 8, 13, 17, 20, 26 Switch circuit

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location H04N 5/93 H04N 5/91 L 5/93 E (72) Inventor Akira Shimazu 6-chome Kitashinagawa, Shinagawa-ku, Tokyo 7th 35th Sony Corporation

Claims (2)

[Claims] 1. A digital signal processing device for recording and reproducing the digital image data in an image transmission system in which time-axis-compressed digital image data is received, and a receiving section for receiving the digital image data, A first recording / reproducing section for recording digital image data on a magnetic tape, and a predetermined portion from the beginning of the received digital image data is recorded in parallel with the recording operation of the first recording / reproducing section, and A second recording / reproducing unit adapted to reproduce the partial data; and, after the second recording / reproducing unit finishes recording the predetermined part of the digital image data, shifts to a reproducing state,
A control means for continuing the time-axis expanded signal reproduced by the first recording / reproducing section with respect to the time-axis expanded signal of the predetermined partial data reproduced by the second recording / reproducing section. A digital signal processing device in an image transmission system characterized by being provided. 2. The digital signal processing device in the image transmission system according to claim 1, wherein the second recording / reproducing device reproduces while recording the digital image data. Digital signal processing device in image transmission system.