Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1994-06-22
2001-04-17
Young, W. R. (Department: 2651)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C360S018000, C360S073060, C386S349000
Reexamination Certificate
active
06219487
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a record mode discriminating apparatus employed in a magnetic recording/reproducing system, and more particularly, to a record mode discriminating apparatus which records signals of a specific frequency band having a predetermined periodicity that varies depending on the recording mode, e.g., standard play (SP) or long play (LP). The signals are recorded with an audio/video signal on a record media in 8 mm camcorder. The record mode discriminating apparatus discriminates a record mode by employing the periodicity of the specific frequency band signal detected when a reproduction is performed in a search mode.
In general, as shown in
FIG. 1
, video tape for 8 mm video equipment utilizes only video region A where an image signal is recorded. The frequency distribution of the signal recorded in video region A is shown in FIG.
2
and includes, a pilot signal, an AFM (Audio FM) signal, a chrominance signal (C), and a luminance signal (Y). Four pilot signals, f
1
, f
2
, f
3
and f
4
, in the band from
100
KHz to
160
KHz, are employed as an automatic track finding (ATF) signal when one frame is constituted by four tracks as is usual. The AFM (Audio FM) signal is in the 1.5 MHz ±100 KHZ band; the chrominance signal (C) is converted into a low frequency band having a center frequency at 743 KHz; and the luminance signal (Y) is in the 4.2 MHz to 5.4 MHz band.
Inasmuch as the length of video tape used as the recording media is limited in image signal recording/reproducing systems, such as a VCR or camcorder, it is desirable to provide a function for recording more information over a long time.
In an analog system, a recording can be made at a lowered speed (1/N), where N is the standard running speed. This allows recording over a longer than standard period with a limited tape length. Thus, a long play (LP) mode or super long play (SLP) mode, where the time period recordable on a given length tape is increased relative to that in a standard play (SP) mode, can be used. The LP mode has a recordable time period twice that of the SP mode by running the tape at half the standard speed, while the SLP mode has a recordable time period three times that of the SP mode by running the tape at one-third of the standard speed.
However, an 8 mm camcorder has only SP and LP modes as record modes, and when a reproduction operation is performed, the system determines whether the signal recorded on the video tape is recorded in the SP mode or LP mode. Normal screen quality can be obtained only if the reproduction is performed in accordance with the determination of the recording mode; i.e., if a signal recorded in LP mode is reproduced in LP mode and if a signal recorded on SP mode is reproduced in SP mode.
In a conventional 8 mm camcorder, when reproduction is performed in a search mode such as fast forward or rewind, the determination of whether the recording mode is LP or SP is made by examining the envelope level of the ATF signal. However, when the envelope level differential between SP and LP mode is small or when noise is included in the ATF signal, discriminating between SP mode and LP mode may be impossible or at least difficult. When the latter occurs, a hunting phenomenon, which causes a periodic rolling undulation, occurs.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide in a magnetic recording/reproducing system a record mode discriminating apparatus, which records signals of a specific frequency band having a predetermined periodicity that varies depending on whether the audio/visual signal is being recorded in the SP or LP mode. During reproduction, the system determines the recording mode of the recorded signal by examining the periodicity of the specific frequency band signal detected when a reproduction is performed in a search mode.
To accomplish the above object, the present invention provides in a magnetic recording/reproducing system, a record mode discriminating apparatus, which records an audio/video signal having a predetermined frequency band and a pilot signal for automatic track finding onto a recording media by means of a read/write head, and reproduces the audio/video signal from the recording media by employing the read/write head, the apparatus comprising: record mode discriminating signal generating means for generating a record mode discriminating signal of a specific frequency band having a periodicity that is varied depending on the record mode; mixing means for mixing the record mode discriminating signal, the audio/video signal and the pilot signal and transferring the mixed signal to the read/write head; detecting means for detecting the record mode discriminating signals from among signals reproduced by the read head; and means for detecting the record mode of said reproduced signals form the discriminating signals detected by the detecting means, whereby the reproduction mode can be carried out at the same mode speed as the record mode at which the signals were recorded.
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Habermehl James L
Samsung Electronics Co,. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Young W. R.
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