Development History
VHS format recorder
In 1976, Japan JVC found VHS format recorder, then in 1982 in order to with Sony video8 (V8) Format Crapping Machine Phases to compete, and the VHS-C (Compact) camera, in accordance with JVC, the JVC of the VHS recorder is increased from the original mono (MONO) to two road Hi-Fi stereo ( STEREO). In 1987, it was a milestone of major changes in household recorders. In this year, the high-quality SupervHS (S-VHS) was officially debuted, and only about 240 lines of the original level of 240 lines were increased to 400 lines, while S-VHS recorder It is still compatible with VHS. With the launch of high-quality HI-VISION TV systems, JVC has developed Japan's domestic special W-VHS format recorders in 1992, which can be used to include Hi-Vision's program and play the Hi-Vision screen.
D-VHS R & D
and D-VHS R & D is to cater to the coming of all-digital high-tech quality TV broadcast era, and several mainly in the design The concept is: (1) Maintaining compatibility with traditional VHS, in order to gradually convert analog video system into digital; (2) as a home server (HOMESERVER) in various applications in multimedia, each volume D -VHS tape capacity can be up to 50GB (using DF-480 tape; GB is 1 billion byte / bit group); (3) using mature VHS technology and existing recorder and video tape production equipment, D-VHS Will be a digital home video format of the excellent value.
How do D-VHS do digital recording? Basically, it is a bitstream of the digital television broadcast program directly on the video tape, and there is no need to pass a special processing or digital coding conversion; when it is in the case, via the external settopbox (conversion box, referred to as STB) or machine The internal receiving decoding device converts the digital signal to analog video and audio signal, and then sent to TV / monitor viewing. STB is essentially a digital TV broadcast receiver. It can also convert digital signals into an analog signal to appreciate the contents of the program. After all, the digital signal cannot be seen directly!
D-VHS multiple recording mode
The digital signal mentioned here is actually MPEG2 encoding signal, because whether it is DirectTV that has been broadcast in the two countries, PerfectV and other digital satellite live TV programs or next-generation DTV (digital TV) is an MPEG2 encoded digital signal, so D-VHS is included in the MPEG2 bitstream, called TS signal, and the record is called MTP (MPEG2TRANSPORTSTREAMPACKET; STB is a digital satellite TV tuning set that contains an MPEG2 decoder.
D-VHS maximum video / transmission bit rate is 28.2Mbps (one million bits per second, BITPERSECOND), the video data when using the DF-420 tape is 44 .4GB (DF-300 is 31.7GB), which means that the future even the digital high-parsing (HD) TV broadcasts of up to 23Mbps can be recorded for three and a half; if the signal is only equivalent to the 2Mbps equivalent to VCD, The icon time can be up to 49 hours.
Basically, the D-VHS has three video modes: the speed of the standard (STD) mode is 16.67mm per second, the video bit rate is 14.1Mbps, 5 hours of video time (DF -300) / 7 hours (DF-420); high speed (HS: highspeed) mode speed is 33.33mm per second, recorded bit rate 28.2Mbps, video time 2.5 hours (DF-300) / 3 .5 hours (DF-420); four low-speed (LS: LOWSPEED) mode, there are four types, respectively, LS2: 8.33mm per second, record bit rate 7Mbps, video time 10 hours (DF-300) / 14 hours (DF-420). LS3: 5.55mm per second, recorded bit rate 4.7Mbps, video time 15 hours (DF-300) / 21 hours (DF-420). LS5: 3.33 mm per second, recorded bit rate 2.8Mbps, video time 25 hours (DF-300) / 35 hours (DF-420). LS7: With 2.88mm per second, record bit rate 2Mbps, video time 35 hours (DF-300) / 49 hours (DF-420).
D-VHS Why have so many video modes? The main reason is to have a variety of broadcast modes to correspond to future DTV, and increase the elastic use space when many recordings, as long as they are within the storage capacity range of the recording tape, you can choose to record multiple channel programs or extended Video time.
Although the bit rate in HD (high parsing) mode is approximately 23Mbps, but sometimes only 14Mbps to play HD program, this time, this time, this time, this time, use STD mode (14.1Mbps) instead of HS mode (28.2Mbps) to record, not only can complete the program, but also prolong the video time of the tape; although the transmission bit rate of each digital TV channel is different, but in the SD (Standard Resolution) mode The average bit rate is probably 3.5Mbps, which is theoretically to include three different 4.7Mbps television channels.
This elastic formation capacity between the priority order of television broadcast quality and the proposed video plan is is one of the main advantages of D-VHS. The 23Mbps of the HS mode is generally equivalent to the amount of information of a live satellite transmitter, and for the broadcast of SD mode, it is equal to six channels.
D-VHS video mode
Whether you choose D-VHS which video mode, and VHS is the drum of 62mm in diameter, the speed is 1800 In addition, the trackwidth is also fixed in 29 micron, just half of the VHS / S-VHS in the SP (Standard Speed) video mode of 58 microns.
In a traditional analog video format, a track (TRACK) is recorded by a field of field; but for the transfer bitstream (TRANSPORTSTREAM, it is mentioned earlier The MPEG2 compression information received by the TS signal is completely different. If a single satellite transmitter sent a broadcast of six channels, then the information of all six channels is received at the same time, so D-VHS must first separate the information of these channels during the TS signal transmission, and resolunch within the individual channel bitstream, the time label is also recorded on the tape to ensure that it can be Read the correct area (Block).
In such a way, the so-called synchronous area (SYNCBLOCK, SB), two SBs are equal to a DataPacket in MPEG2, which is the MTP recording mode.
D-VHS includes three parts of an outerparity, a mainparity, a subData (SUBDATA). In addition to erroor-correctioncode, in addition to the outer part of the same area, in Subdata, it also provides incorrect correction information to achieve accuracy of video and hopping; the recorded in the main data area is The received audio and video information contains 336 SBs in the main data area; and the correct location (address) and the necessary chapter / index (CHAPTER / INDEX) data are made as a search (SEARCH) feature. According to the use, these information is not transmitted from the television broadcast, but the D-VHS recorder is generated inside when the video is recorded, and the automatic record is on the video tape, and there is also SB in the sub-data area, but only four A.
D-VHS About the head structure of the recording angle, in general STD and LS3, LS5, LS7 video mode, only two heads, if you want to use the LS2 mode, you must add a magnetic head. And turn into three heads to HS mode, four heads, of course, this time all video mode can be used.
In the D-VHS standard, IEEE1394 has been used as its digital interface. The IEEE1394 terminal is a DV terminal, but also known as I. The LINK terminal, it started to be used on a full digital DV camera / record player. Here, it is necessary to mention that the digital signals outputted by the IEEE 1394 terminals of D-VHS have anti-copy signals to the corresponding copyright protection, which is recognized via DTLA (Digital Transmission Management).
See here, think that smart friends may say that D-VHS and DV camera / recorders have DV terminals, just able to make digital contractions, sorry! That is not good! How can I do this? Because D-VHS and DV are two completely different formats, it is naturally incompatible. The DV is 4: 1: 1 color difference numeral (CommponentDigital, also known as component digital record) 8-bit quantification, the brightness signal sampling frequency is as high as 13.5MHz, the color signal sampling frequency is also as high as 3.375MHz, and the video compression ratio is only 5: 1, the information transmission bit rate reaches 25Mbps; while D-VHS is primarily recorded by MPEG2 digital signals, the video compression ratio is approximately 30: 1 to 40: 1. The transmission bit rate is 14.1Mbpx in STD mode. Therefore, through the DV terminal, D-VHS and DV are simply unable to directly compute, and the technical specifications are good than D-VHS.
D-VHS model has been listed in
Next to introduce several D-VHS recorders in Japan's new listing in Japan. First let's see Hitachi's DT-DR3000 and DT-DR5000, these two have MPEG2 encoders and decoders, indicating that the received analog BS live satellite program with General TV programs or other traditions. Video source code is MPEG2 digital signal to do D-VHS format video, then the decoder can be placed, and they can also record VHS, S-VHS format, and the D-VHS section only STD video mode, two The only difference is that the DT-DR5000 has more IEEE1394 I. Ink terminal, DT-DR3000 price is not tax 148000 yen, D-DR5000 does not include tax sold 200,000 yen. SLD-DC1 is the first D-VHS recorder launched by SONY, equipped with I. Ink terminal, pricing does not include tax only 14000 yen, but it needs to match the SAS-MS9SET digital CS tuner (62000 yen does not contain tax), via I. The INK terminal feeds the TS signal of MPEG2 to the SLD-DC1 in D-VHS video, and then it is raided again by i. The LINK terminal transmits the signal back to the SAS-MS9SET, and the MPEG2 decoder is used inside, and the decoded audio and video signal is output to the SLD-DC1, and then output to the TV / monitor, the SLD-DC D-VHS is the same. Only STD mode is only recorded in VHS format.
JVC's HM-DR10000 can be said to be a more complete D-VHS video recorder in the market, not only equipped with an MPER2 encoder and decoder, not only the analog video signal is converted to a number. The signal is D-VHS video, which also has a DV decoding line, which can pass I. The DV compressed signal is restored by the LINK terminal, and then MPEG2 encoding is made so that the D-VHS video is recorded. In addition to the STD, there is an LS3 mode, and the HM-DR10000 is also a quite advanced S- VHS recorder, pricing does not contain sharp 198,000 yen. These four four models are the latest D-VHS recorders.
喔! correct! By the way, everyone is that D-VHS record must use a special videotape, the outer surface it and the traditional S-VHS strip is only recognized by the IDHole. The price of D-VHS tape on Japan in 2013, DF-300 is 2000 yen, and DF-420 is 3,500 yen.
D-VHS format The supporters in technology are Hitachi, Philips (Philips) and Matsushita Electric (Matshita), withdrew the hardware manufacturer, which agrees with this format, Toshiba, South Korea Samsung, Sanyo, Sharp, Sony, Nanhan Daewoo (Daewoo), Mitsubishi (Mitsubishi), etc., the videos manufacturers have Konica, Sumitomo 3M, TDK, BASF, Maxell and Fuji.
All friends should have a clearer understanding of D-VHS, and the D-VHS recorder is not necessarily compatible with S-VHS, which is likely to be compatible with VHS (such as Sony model). It seems that the emergence of D-VHS is not just to extend the life of the VHS system, but propose a new video concept, digital technology development is really unlimited!