Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
2000-08-03
2004-08-03
Tran, Thai (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C386S349000
Reexamination Certificate
active
06771882
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a data transmission apparatus adapted to reproduce digital data from a tape-shaped recording medium in a format corresponding to the recording format of the tape-shaped recording medium that is used for recording the data of a frame including video data on an odd number of tracks and then transmit the reproduced data. The present invention also relates to a data transmission method to be used for such a data transmission apparatus.
2. Related Background Art
Recently, digital video tape recorders equipped with a video camera and console type digital video tape recorders are marketed for home use. Such digital video tape recorders are adapted to record digital video signals and digital audio signals on a magnetic tape.
A recording format referred to as DV format is known and used with digital video tape recorders of the above described category (IEC 61834 helical scan digital video tape cassette recording system using 6.35 mm magnetic tape for consumers (525/60, 625/50, 1125/60 and 1250/50 systems). With the DV format, the video signals to be recorded are compressed typically by means of a technique of so-called discrete cosine transform and a high data recording density is realized to make it possible to record high quality images for a long period of time than ever.
More specifically, with the DV format, video data are recorded in two recording modes (SD mode, SDL mode) that are different from each other in terms of compression ratio in order to achieve an optimal recording efficiency for any program that may be transmitted at any of a variety of bit rates.
In the recording mode for the higher recording efficiency (SDL mode), the compression ratio is made higher than that of the ordinary recording mode (SD mode) by using only a half of the amount of information of the SD mode and reducing the running speed of the magnetic tape to a half of that of the SD mode for recording/reproducing data. Then, data are recorded intermittently on the magnetic tape by way of the magnetic head in the SDL mode. In other words, in the SDL mode, data are not recorded continuously on the magnetic tape in terms of time and the number of times of recording data on the magnetic tape by way of the magnetic head is reduced to a half of that of the SD mode so that the magnetic tape may allow a total recording time twice as long as that of the SD mode. Then, useless data in the form of stuffing bytes and/or packs containing no information of a program that reduce the recording efficiency in the SD mode because of the low bit rate of the mode can be prevented from being recorded on the magnetic tape in the SD mode to consequently improve the recording efficiency.
Now, the DV format will be discussed further along with the SD mode and the SDL mode that are used for the DV format.
FIG. 1
is a schematic illustration of the track pattern of a 6.35 mm wide magnetic tape adapted to record digital data in the DV format (hereinafter referred to as DV tape).
In the DV format, data including video data are recorded on a 6.35 mm (=¼ inch) wide DV tape by way of a rotary drum. The rotary drum is typically provided with a pair of magnetic head with different azimuth angles (±20°). Then, the paired magnetic heads are made to scan the magnetic tape with a predetermined angle relative to the running direction of the tape to produce a track pattern of data-carrying tracks with two different azimuth angles that are arranged alternately as shown in FIG.
1
.
Now, assume that every ten consecutive data-carrying tracks form a unit on the DV tape and track numbers of
0
through
9
are assigned to the ten tracks of each unit as shown in FIG.
2
. Also assume that the tracks carrying the data recorded by one of the magnetic heads are referred to as even tracks E
0
, E
2
, E
4
, E
6
and E
8
, whereas those carrying the data recorded by the other magnetic head are referred to as odd tracks O
1
, O
3
, O
5
, O
7
and O
9
to indicate the recording sequence. It will be appreciated that data are recorded on the tracks in the order of E
0
,
01
, E
2
and so on.
In the SD mode, the digital data of a frame are recorded on the ten tracks (with track numbers
0
through
9
) of a unit out of a video signal of the NTSC system.
In the SDL mode, on the other hand, the digital data of two frames are recorded on the ten tracks (track numbers
0
through
9
) of a unit out of a video signal of the NTSC system. More specifically, in the SDL mode, the digital data of a frame are recorded on the front five tracks (with track numbers
0
through
4
) of a unit and the digital data of another frame are recorded on the rear five tracks (with track numbers
5
through
9
) of the unit. Therefore, hereinafter, the frame recorded on the front five tracks (with track numbers
0
through
4
) of a unit is referred to as front frame and the frame recorded on the rear five tracks (with track numbers
5
through
9
) of the unit is referred to as rear frame.
Additionally, all the data recorded on each track are subjected to a 24/25 transform in the DV format. As the data to be recorded are subjected to a 24/25 transform, a pilot signal for ATF (automatic track finding) is laid on the entire track. Therefore, the magnetic head is made to readily operate for tracking by detecting the pilot signal when reproducing the recorded data. With the 24/25 transform, an extra bit (1 byte) is added to every 24 bits (3 bytes) of data to lay three low frequency pilot components on the string of the data to be recorded. More specifically, the run length of the data to be recorded is made not greater than 9 and pilot signal components with frequencies f
0
, f
1
and f
2
are laid on the data-carrying tracks. Then, in the DV format, typically the pilot signal component with frequency f
0
is laid on the even tracks E
0
, E
2
, E
4
, E
6
and E
8
, while the pilot signal components with frequencies f
1
and f
2
are laid alternately on the odd tracks O
1
, O
3
, O
5
, O
7
and O
9
. Thus, a repetitive pattern of frequencies of . . . , f
0
, f
1
, f
0
, f
2
, f
0
, f
1
, f
0
, f
2
, . . . appears on the tracks for the pilot signal. As a result of recording a pilot signal showing such a pattern of frequencies, when the magnetic head is made to scan a track with a pilot signal component having the frequency of f
0
in order to reproduce the recorded data, the pilot signal components with frequencies f
1
and f
2
are obtained as cross talk signal so that the magnetic head can be reliably made to operate for tracking.
A rotary drum
101
provided with three magnetic heads as shown in
FIG. 3
is typically used for recording data both in the SD mode and the SDL mode. Referring to
FIG. 3
, CH0 head
102
and CH1 head
103
are arranged squarely opposite to each other on the rotary drum
101
with the axis of rotation of the drum disposed therebetween. The azimuth angle of the CH0 head
102
shows a positive value, whereas that of the CH1 head
103
shows a negative value. Additionally, CH2 head
104
is arranged on the rotary drum at a position upstream relative to the CH0 head
102
and displaced by 90° therefrom in the sense of rotation of the rotary drum.
The CH0 head
102
and the CH1 head
103
are used for recording in the SD mode, whereas the CH2 head
104
is left unused. In the SD mode, the DV tape is made to run at a constant speed of 18.8 mm/s while the rotary drum
101
is driven to rotate at a rate of 9,000 rpm. As shown in
FIG. 4
, the CH0 head
102
and the CH1 head
103
are consecutively switched from one to the other by a 150 Hz ({fraction (1/150)} second cycle) head SW signal for the operation of signal recording. Thus, an amount of information good for two tracks is recorded while the rotary drum is driven to make a full turn in the SD mode. Therefore, the tracks carrying the data recorded by the CH0 head
102
showing a positive azimuth angle and the tracks carrying the data recorded by the CH1 head
103
showing a negative azimuth angle are arranged alte
Imai Kenichiro
Nara Yuka
Frommer William S.
Frommer & Lawrence & Haug LLP
Sony Corporation
Tran Thai
LandOfFree
Data transmission apparatus and data transmission method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Data transmission apparatus and data transmission method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Data transmission apparatus and data transmission method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3324230