Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1999-11-08
2002-10-22
Boccio, Vincent (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C375S366000, C375S368000
Reexamination Certificate
active
06470142
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a data recording apparatus, a data recording method, a data recording and reproducing apparatus, a data recording and reproducing method, a data reproducing apparatus, a data reproducing method, a data record medium, a digital data reproducing apparatus, a digital data reproducing method, a synchronization detecting apparatus, and a synchronization detecting method that are used for recording and/or reproducing a digital video signal and a digital audio signal.
2. Description of the Related Art
A data recording and reproducing apparatus that records a digital video signal and a digital audio signal to a record medium and that reproduces a digital video signal and a digital audio signal therefrom is known. A typical example of such an apparatus is a digital VTR (Video Tape Recorder). In a record processing portion of a digital video signal recording apparatus, digital video data and digital audio data are placed packets with a fixed length. ID information is added to each packet. The packetized data is encoded with an error correction code. A synchronous pattern and ID information are added to packetized data, an error correction code parity, and so forth so as to form a sync block. A plurality of sync blocks are grouped as a sector corresponding to each data type. Each sector as serial data is recorded on a magnetic tape by a rotating head. The length of each sync block in the same sector is the same. The sync blocks are successively assigned unique ID numbers. The ID information has the same value. A product code is used as an error correction code. In other words, a two-dimensional array of data symbols is encoded with an outer code in the vertical direction and an inner code in the horizontal direction. Thus, each symbol is dually encoded. One minimum data encoding/decoding unit of the product code is referred to as ECC block.
On the reproducing side, the start position of each sync block is detected with a synchronous signal. Packets in each sync block are rearranged corresponding to ID numbers and ID information. Since a unique synchronous pattern is added at the start position of each sync block, using the bit sequence of the synchronous pattern, the pattern occurrence interval, successive ID numbers in the same sector, and the same ID information, the phase of a synchronous block can be detected. In other words, when the conditions that the bit sequence of a synchronous pattern matches a fixed pattern, that the same pattern is detected at a position delayed by the block length, and that the block ID is proper are satisfied, the phase of the synchronous block is detected. In the format of such a conventional digital VTR, to easily perform the synchronization detecting process, the length of each synchronous block is fixed (to one type) regardless of the data type.
To record and reproduce video data, a compression encoding process is performed. When video data corresponding to MPEG (Moving Picture Experts Group) standard is compression-compressed, coefficient data generated by DCT (Discrete Cosine Transform) process is encoded with a variable length code. When the amount of data that is recorded per track or every a predetermined number of tracks is fixed, the data amount of the variable length code that is generated in a predetermined time period is limited to a predetermined value. Variable length code encoded data (namely, variable length data) is packed in data areas of a plurality of sync blocks corresponding to a predetermined time period.
The data amount of a digital audio signal is not so large in comparison with that of a digital video signal. To prevent the audio quality from deteriorating in the compressing process and to prevent a complicated process because the data access unit of an MPEG audio signal does not match a video frame and a video signal and an audio signal are switched, non-compressed audio data (linear PCM) is recorded and/or reproduced.
There are as many as 18 types of digital television broadcasting formats in the United States. In such an environment, a digital VTR that can record and reproduce video data in a plurality of formats is desired. When the length of each sync block is fixed to one type regardless of data types as with the conventional digital VTR, although synchronization is easily detected, it is difficult to record data in various formats. Next, this point will be described.
Next, an example of the conventional digital VTR will be described. The VTR records video data and audio data on a tape in a tape format as shown in FIG.
1
A. As shown in
FIG. 1A
, data of six tracks is recorded per frame. One segment is composed of two tracks with different azimuths. In other words, six tracks are composed of three segments. A pair of tracks that compose one segment are assigned track numbers [0] and [1] corresponding to the azimuths. Video sectors are formed on both edges of each track. Video data is recorded on the video sectors. An audio sector is formed between the two video sectors. Audio data is recorded on the audio sector.
In the track format shown in
FIG. 1A
, audio data of four channels can be handled. Referring to
FIG. 1A
, A
1
to A
4
represent sectors of channels
1
to
4
of audio data, respectively. The video data is shuffled (interleaved) and recorded on sectors on the upper side and the lower side. A system area (sys) is formed at a predetermined position of each video sector on the lower side. In
FIG. 1A
, SAT
1
(Tr) and SAT
2
(Tm) are areas in which a servo lock signal is recorded. In addition, gaps (Vg
1
Sg
1
, Ag, Sg
2
, Sg
3
, and Vg
2
) with predetermined sizes are formed between individual record areas.
As shown in
FIG. 1B
, data recorded on the tape is composed of a plurality of blocks that are equally divided (these blocks are referred to as sync blocks).
FIG. 1C
shows an outlined structure of one sync block. One sync block is composed of an ID (that identifies the current sync block), a DID (that represents the contents of data that follows), a data packet, and an error correction inner code parity. Data is recorded and reproduced as sync blocks (the minimum data recording/reproducing unit is one sync block). For example, a video sector is composed of many sync blocks that are arranged.
One sync block is composed of a synchronous signal, an ID, a data packet, and an inner code parity. Now, one sync block is denoted by
sync block: sync pattern+sync id+data packet+inner parity.
Design condition: The length of one data packet of video data is the same as the length of one data packet of audio data.
Next, as an example of the recording process of video data, the following video data and conditions are considered.
Video data (4:2:2)
Design conditions: Data compression ratio=2 or more (the data amount after data compressing process is 1/2 or less of the data amount before data compressing process).
10 DCT blocks are packed to two sync blocks.
6 tracks per field.
-[525 lines/60 fields] format video signal-
Amount of video data per field:
512×720×(8+4+4) bits/8/2=368640 bytes
Number of DCT blocks per field:
512×720/8/8=5760
10 blocks/2 syncs→1152 sync blocks
Length of data packet>368640×(1/2)/1152=160 (1)
-[625 lines/60 fields] format video signal-
Amount of video data per field:
608×720×(8+4+4) bits /8/2=437760 bytes
Number of DCT blocks per field:
608×720/8/8=6840
10 blocks/2 syncs→1368 sync blocks
Length of data packet>437760×(1/2)/1368=160 (2)
An example of the recording process for audio data is as follows:
-Audio data (24 bits, 48 kHz sampled)-
Design condition: Non-compression
AUX data: 6 bytes per field
Number of samples per field in [525/60] format:
48 k/59.94 Hz×24 bits/8=2402.4 bytes
(5 field sequence)
AUX data of 12 bytes→2415 bytes (total data amount)
Number of samples per fiel
Isozaki Masaaki
Oyone Yoshio
Boccio Vincent
Frommer William S.
Frommer & Lawrence & Haug LLP
Kessler Gordon
method apparatus, and synchronization detecting
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