Okamoto, et al.: A Consumer Digital VCR for Advanced Television
`
`199
`
`A CONSUMER DIGITAL VCR FOR ADVANCED TELEVISION
`Hiroo Okamoto, Masafumi Nakamura, Yuji Hatanaka, Shigeru Yamazaki,
`Takaharu Noguchi, and Takao Arai
`Image & Media System Laboratory, Hitachi, Ltd.
`
`ABS TRACT
`A prototype of a consumer digital VCR
`for ATV has been developed. This VCR can
`record a compressed digital HDTV signal for 4
`hours whose data rate i s about 20 Mbps.
`
`1. Introduction
`The development of Advanced Television
`(ATV) system is now in progress. To meet
`the demand for an early realization of a VCR
`for the ATV system, we have developed a
`prototype consumer digital VCR for the ATV
`system which can be
`implemented by
`the
`current VCR technology. This VCR records a
`compressed digital HDTV signal whose data
`rate
`the
`is 21.6 Mbps. At playback,
`reproduced signal
`is decompressed
`to
`the
`HDTV signal by an ATV decoder.
`In this paper, the technology adopted in
`the prototype VCR is described.
`
`Table 1 Concept of the Digital VCR
`for ATV System
`
`Item
`
`Tape Width
`
`Tape Material
`Drum Diameter
`
`Recording Time
`
`Specification
`inch
`
`1/2
`
`y -Fe203
`62 mm
`
`4 hour
`
`2. Basic Concept
`Table 1 shows the basic concept of the
`digital VCR for the ATV system. To realize a
`low cost digital VCR, we
`focused on
`trans fer
`tech no 1 o g y
`from
`current
`analog
`VCRs. Although, we have adopted a 1/2-inch
`oxide tape and a drum diameter of 62 m m
`because they are widely used in the current
`analog VCRs, our goal for the recording time
`is more than four hours.
`Because the main issue for this concept
`is the possible recording bit rate, we have
`done experiments on a various recording bit
`rate.
`
`3. Examination of The Recording Bit
`Rate
`the
`Fig. 1 shows the relation between
`symbol error rate (1 symbol = 8 bits) and the
`signal-to-noise ratio (Vpp/Nrms) which
`is
`measured by a
`transmission
`characteristic
`simulator. It is necessary for the digital VCR
`to attain the symbol error rate of less than
`1 X lo-’. Therefore, the signal-to-noise ratio
`should be higher than 24 dB.
`the
`Fig.2 shows the relation between
`signal-to-noise ratio and the recording bit rate
`tape and metal
`with both oxide ( y -Fe,O,)
`powder
`tape on
`the conditions
`that
`the
`scanning speed is 5.8m/s and the track pitch
`is 19 p m . According to this figure, the
`
`Manuscript received June 11, 1993
`
`0098 3063/93 $03.00 @ 1993 IEEE
`
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`IEEE Transactions on Consumer Electronics, Vol. 39, No. 3, AUGUST 1993
`
`recording bit rate of 20 Mbps is possible with
`oxide tape.
`This means that the VCR can record the
`signal whose data rate is as high as 40 Mbps
`with the two-channel recording, because of
`simultaneous recording with two heads. And,
`four-hour recording would be possible when
`we use an equivalent cassette size as VHS and
`a tape thickness of 15 ,U m .
`Therefore, we have adopted a recording
`format described in the next section for the
`digital VCR whose recording bit rate is about
`40 Mbps.
`
`4. Recording Format
`The digital VCR records the compressed
`digital HDTV data of t h e ATV system.
`This data is transmitted as two priority
`classes which are for high priority (HP) data
`and for standard priority (SP) data. Fig.3(a)
`shows the packet format of the HP and SP
`data. The packet consists of 148-byte data
`including a packet sync code, header data and
`a
`forward
`error
`correction
`code. Data
`transmission rates are 4.32 Mbps for the HP
`data and 17.28 Mbps for the SP data. Total
`
`1 0 3 ,
`
`1
`
`a
`
`L
`
`2 104
`9
`I5 B
`5
`
`1 0 - ~
`
`108
`
`1 o - ~
`
`Signal-to-Noise Ratio [dB]
`
`Fig.1 Symbol Error Rate vs. Signal-to-Noise Ratio
`
`35
`
`:
`
`v=5.8m/s, Tp=19 p m
`
`l5
`
`l b
`
`20
`Recording Bit Rate [Mbps]
`
`30
`
`Fig.2 Signal-to-Noise Ratio vs. Recording Bit Rate
`
`1 Packet
`
`
`
`Video, Audio or Aux Data Video, Audio or Aux Data
`
`
`
`FEC Code FEC Code
`
`
`
`a a
`
`
`I I
`
`I I
`
`(b)
`
`Sync
`
`Block
`Address
`
`HP or SP Packet Data
`
`1 Block
`
`Error Correction
`code
`
`r
`
`Fg.3 Data Recording Format of Digital VCR
`
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`Okamoto, et al.: A Consumer Digital VCR for Advanced Television
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`
`transmission rate is 21.6 Mbps.
`The VCR records these packet data with
`a block format. Fig.3(b) shows the block
`format of the recording data. A block consists
`of one packet data with a block sync code,
`block address data and error correction code.
`
`Fg.4 Track Format of Digital VCR
`
`Table2 Specifications of the Digital VCR
`
`Drum Speed
`
`Number of Heads
`
`I
`I 21.6 Mbps
`I Transmission Rate
`I Error Correction Code I Reed-Solomon Code I
`1 Modulation Method
`I 8-10 Modulation
`I
`
`Recording Bit Rate
`
`Tape Speed
`
`Track Pitch
`
`Minimum Wave Length
`
`36.8 Mbps
`
`22.24 mmls
`
`19
`pm
`0.64 p m
`
`(packet)
`The VCR records 180 block
`data in a track. Fig.4 shows the track format.
`A track consists of three areas that are one
`HP data area and two SP data areas. The VCR
`records
`60
`block
`data
`in
`each
`area.
`Considering dropouts on
`the
`tape
`and
`reduction in quantity of reproduced data at
`trick play, we have recorded
`the HP data
`doubly in the HP data area.
`
`5. Main Specifications
`Table 2 shows main specifications of
`the digital VCR for the ATV system.
`A drum speed is 1824.3 revolutions per
`minute. This drum speed comes from
`the
`packet data rate of the ATV signal. At this
`speed, the VCR can record 180 packet data in
`each track.
`The VCR uses the Reed-Solomon code
`for error correction.
`Recording data are modulated based on
`an 8-10 modulation method which is the same
`that of the Digital Audio Tape
`method as
`(DAT) system. This method is suitable for
`magnetic recording, because a low frequency
`component of recording signal is reduced. The
`recording bit rate after modulation is 18.4
`Mbps per channel. The total recording bit rate
`is 36.8 Mbps because of
`two
`channel
`recording.
`A tape speed is 22.24 mm/s and a track
`pitch is 19 p m. A minimum wave length is
`0.64 p m .
`
`6. Recording and Reproducing
`Characteristics
`Fig.5 shows the power spectrum of the
`reproduced signal. Fig.S(a) shows the power
`spectrum of the system noise. Fig.S(b) shows
`the power spectrum of the reproduced signal
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`(9.2
`when a maximum recording frequency
`MHz) signal is recorded. Fig.S(c) shows the
`power spectrum of
`t h e reproduced signal
`when 8-10 modulated signal is recorded. A
`head width is 23 ,u m. A signal-to-noise ratio
`of 27.2 dB (Spp/Nrms, Signal freq.= 9.2
`MHz) has been obtained.
`
`Tw = 23 pm, Tp = 19pm
`
`10 dB/div
`
`SPAN 20 MHz, CENTER 1 OMHz
`
`Fig.5 Power Spectrum of Reproduced Signal
`
`Tw=23 pm,Tp=19pm, 0 =f20'
`
`Fig.6 shows the power spectrum of a
`talk signal
`from an adjacent
`track.
`cross
`Fig.6(b) shows the power spectrum of the
`reproduced signal when 9.2 MHz signal is
`recorded on
`t h e measured
`track and 8-10
`modulated signal is recorded on the adjacent
`track. An azimuth angle of the head is *20
`degree. This cross taIk signal degrades
`the
`signal-to-noise ratio of about 2 dB. Therefore,
`the total signal-to-noise ratio is 25.2 dB.
`the
`Fig.7 shows an eye pattern of
`reproduced signal. We have obtained a symbol
`error rate of less than 3 X los6.
`
`the
`
`7. Structure of The Digital VCR
`Fig.8 shows a block diagram of
`digital VCR for the ATV system.
`A recording circuit of the VCR consists
`of an
`interface circuit, a memory and two
`channel encoders. A reproducing circuit of the
`VCR consists of two channel PLL circuits,
`two channel decoders, a memory and an
`interface circuit .
`At recording, t h e ATV decoder sends the
`demodulated packet data to the VCR. The
`interface circuit of
`the VCR receives
`this
`data, and stores in the memory. Encoders read
`
`10 dB/div
`
`SPAN 20 MHz, CENTER 1 OMHz
`
`Fig.6 Power Spectrum of Cross Talk
`
`Fig.7 Eye Pattern of Reproduced Signal
`
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`Okamoto, et al.: A Consumer Digital VCR for Advanced Television
`
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`
`Fig.8 Block Diagram of the DigitalVCR
`
`packet data from the memory, and convert this
`data into the block format of the VCR. These
`block structured data are recorded on the tape
`by two rotary heads s im u 1 t aneou s 1 y .
`At playback, the decoders of the VCR
`correct errors of
`the reproduced data by
`Reed-Solomon code. After correction,
`the
`decoders convert
`the data
`into
`the packet
`format of the ATV system, and store these
`data in
`the memory. The interface circuit
`reads the packet data from t h e memory, and
`sends these data to the ATV decoder. The ATV
`decoder decompresses the received packet data
`to the HDTV signal and audio signal.
`
`7. Conclusions
`(1) A prototype of digital VCR for the ATV
`system has been developed.
`(2) This VCR records the compressed digital
`HDTV signal of the ATV system.
`(3) The total recording bit rate is 36.8 Mbps
`(18.4 Mbps per channel) and the maximum
`
`recording time is 4 hours with oxide tape.
`(4) We have confirmed that it is possible to
`produce a low cost consumer digital VCR
`for the ATV system with the current VCR
`tech no logy.
`
`ACKNOWLEDGMENT
`The authors would like to thank the
`members of Advanced Television & Systems
`Laboratoly, Hitachi America, Ltd. for their
`assistance in the development of this VCR.
`
`REFERENCES
`[ l ] "Advanced Digital Television: Prototype
`Hardware Description" submitted to FCC
`SS/WPl by ATRC, February 1992.
`[2] Y.-S.Ho, C.Basile and A.Miron, "MPEG-
`Based Video Coding for Digital Simul-
`casting", International Workshop on HDTV
`'92 Proceedings,Vol. 1. November 1992.
`
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`
`B IOGRAP H I E S
`
`IEEE Transactions on Consumer Electronics, Vol. 39, No. 3, AUGUST 1993
`
`Hiroo Okamoto is a senior
`researcher in the 3rd dept. at
`Image & Media System
`Laboratory, Hitachi Ltd.,
`Yokohama, Japan. He receiv-
`ed the B.S degree and the M.S
`degree from Kumamoto Univ-
`ersity in 1980. Since then, he
`has been with Hitachi and
`engaged in the development of
`digital audio and video
`products, especially in the
`field of signal processing
`circuits.
`
`Masafumi Nakamura is a
`researcher in the 3rd dept. at
`Image & Media System
`Laboratory, Hitachi Ltd.,
`Yokohama, Japan. He receiv-
`ed the B.S degree from Keio
`University in 1981. Since
`then, he has been with Hitachi
`and engaged in the develop-
`ment of digital audio and
`video products.
`
`Yuji Hatanaka is a researcher
`in the 3rd dept. at Image &
`Media System Laboratory,
`Hitachi Ltd., Yokohama,
`Japan. He received the B.S
`degree and the M.S degree
`from Nagoya University in
`1984. Since then, he has been
`with Hitachi and engaged in
`the development of digital
`signal processing circuits.
`
`is a
`Shigeru Yamazaki
`researcher in the 3rd dept. at
`Image & Media System
`Laboratory, Hitachi Ltd.,
`Yokohama, Japan. He gradua-
`ted from Osaka Prefectural
`Technical College in 1975.
`Since then, he has been with
`Hitachi and engaged in the
`development of digital audio
`and video products, especially
`in the field of magnetic
`recording technology.
`
`Takaharu Noguchi is a senior
`researcher in the 3rd dept. at
`Image & Media System
`Laboratory, Hitachi Ltd.,
`Yokohama, Japan. He receiv-
`ed the B.S degree from
`Hiroshima University in
`1973. Since then, he has
`been with Hitachi. Since
`1979, he has been engaged in
`the development of digital
`audio and video products.
`
`is a chief
`Takao Arai
`researcher in the 3rd dept. at
`Image & Media System
`Laboratory, Hitachi Ltd.,
`Yokohama, Japan. He received
`the B.S degree from Keio
`University in 1968. Since then,
`he has been with Hitachi and
`worked on advanced tape
`recorders and noise reduction
`system. Since 1978, he has
`been engaged in the develop-
`ment of digital audio and video
`products such as PCM proce-
`ssors, CD players, receiver for
`DBS, DATs, VCRs and so on.
`
`ATI Technologies ULC
`Ex. 2005
`LG Electronics, Inc. v. ATI Technologies ULC
`IPR2015-00321