Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1999-11-08
2003-11-25
Boccio, Vincent (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000, C386S349000, C375S240250
Reexamination Certificate
active
06654544
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a video data recording apparatus, a video data recording method, a video data reproducing apparatus, a video data reproducing method, a video data recording and reproducing apparatus, and video data recording and reproducing method applicable for video data corresponding to for example MPEG2 (Moving Picture Experts Group Phase 2) standard.
2. Description of the Related Art
As exemplified with a digital VCR (Video Cassette Recorder), a data recording and reproducing apparatus that records a digital video signal to a record medium and that reproduces the digital video signal therefrom is known. Since the information amount of the digital video signal is large, it is compressed. As an example of an encoding process for compressing the data amount of moving picture data, inter frame motion compensation predictive encoding process is known. As such an encoding standard, the MPEG2 standard is known.
When picture data corresponding to the MPEG2 standard is recorded and reproduced, all an elementary stream (ES), a packetized elementary stream (PES), and a transport stream (TS) can be recorded and reproduced. The ES is a bit stream that an encoder outputs and that is composed of access units corresponding to video frames. The PES is a packetized ES. Each packet has a PES header. The TS is segmented with packets whose length is 188 bytes each. Data of the PES is divided into packets. Each packet contains a TS header.
MPEG data has a hierarchical structure. The highest layer of the hierarchy is a sequence layer. The sequence layer is followed by a GOP (Group Of Picture) layer, a picture layer, a slice layer, a macro block layer, and a block area. In the MPEG standard, data contained in each layer is defined. The block layer that is the lowest layer contains DCT coefficient data generated corresponding to the DCT (Discrete Cosine Transform) process. One macro block is composed of four blocks of a luminance signal and one or two blocks of a color difference signal. Thus, one macro block contains a total of six blocks or eight blocks of coefficient data. The coefficient data is encoded with a variable length code. Macro block mode data that represents a macro block type is added to a macro block that has been encoded with the variable length code.
When PEG data is recorded or reproduced by a digital VCR in the environment of a broadcasting station, it is advantageous to record and reproduce an ES rather than a TS because the delay becomes the minimum and the switching timing becomes clear. These features are very important for a VCR used in a broadcasting station. As an interface for an ES in the MPEG standard, SDTI-CP (Serial Data Transform Interface Content Package) interface can be used. There are following differences between an ES in the SDTI-CP format and a TS in the MPEG format.
In the SDTI-CP format:
Clock synchronization: H/V synchronous signal of SDI
Frame synchronization: Frame synchronous signal of SDI
Decode delay: one frame (two frames for END and DEC)
In the MPEG-TS format:
Clock synchronization: PCR
Frame synchronization: PTS/DTS of PES
Decode delay: Several frames (depending on vbv delay)
As is clear from the comparison, it is advantageous to use an TS in the case that a synchronous signal cannot be transmitted between two far points by another means. However, in a broadcasting station, all operations are performed using a single synchronous signal named house sync. Thus, a synchronous signal can be easily obtained. Consequently, it is not necessary to place a synchronous signal PCR (Program Clock Reference) on a stream. This applies to frame synchronization. A time reference termed time code is totally used in the broadcasting station. Thus, new time stamps such as PTS (Program Time Stamp) and DTS (Decoding Time Stamp) of a PES are not required.
More importantly, a transmission system that performs encoding/decoding processes with a small delay is required. In the case of the MPEG-TS, a vbv buffer (that the encoder estimates as the storage capacity of a buffer on a decoder side) is used to smooth the transmission rate. When the size of the buffer is large, the delay of the decoder becomes large.
On the other hand, in the SDTI-CP, with a sufficient transmission band, a stream (video data, audio data, additional data, and so forth) of one frame can be transmitted as bursts. Thus, since the frame is immediately preceded by a synchronous signal thereof, a switching operation can be performed on a transmission path for video data, audio data, additional data, and so forth. In addition, unlike with the MPEG-TS, it is not necessary to take a time for storing data to the vbv buffer. Thus, in the next frame, data can be decoded. Because of such a reason, it is preferred that a digital VCR used in a broadcasting station can input an ES, record it on a tape, and output data reproduced from a tape as an ES.
When an ES is recorded and reproduced by a VCR, because of the characteristics thereof, with the syntax of the MPEG standard, a problem takes place. In the MPEG2 standard, a variable length code is used. As a data synchronization detecting system for data, (1) preceded by (0) of 23 bits is used as a start code. The minimum unit of the lowest hierarchical layer is a slice. Normally, one slice is composed of one stripe (16 lines). With one stripe, a variable length code starts with the left edge of the screen and ends with the left edge thereof.
When an MPEG ES of which one slice is composed of one stripe is recorded on a tape by a VCR, the resistance against an error is weak. Even if one error takes place in the slice, the error propagates to the right edge of the screen. The error cannot be restored until the next slice header is detected. When a variable speed reproducing operation of which part of data is reproduced is performed, only a portion followed by a variable length code is reproduced. Thus, a reproduced portion concentrates at the left side of the screen. Consequently, the screen cannot be equally updated. In addition, when a high speed reproducing operation is performed, the arrangement of data on the tape cannot be predicted. Thus, when a tape pattern is traced at predetermined intervals, the screen cannot be equally updated.
Moreover, in the MPEG syntax, the maximum slice length (maximum macro block length) is not limited. Thus, data whose data amount becomes larger than the original video data is permitted. In this case, it takes a long time to perform a process for rearranging coefficients every macro block. Thus, since a buffer is required, a system delay becomes large.
In association with the rearranging process for coefficients every macro block, a packing process will be described. In a VCR, to simplify signal processes for the recording operation and the reproducing operation, a synchronous signal and an ID are added to data with a predetermined length so as to form sync blocks. A process for packing data in the data area of a sync block is referred to as packing process. The packing process is performed on the recording side. In contrast, a process for removing data from the data area of a sync block is referred to as depacking process. The depacking process is performed on the reproducing side. When a product code is used, data is packed in one line of an ECC (Error Correcting Code) block of the product code.
In a VCR, the amount of data that can be recorded every track or every a predetermined number of tracks is fixed. Thus, the data amount of a variable length code generated in a predetermined time period is controlled so that it does not exceed a predetermined value. Data encoded with a variable length code is packed in data areas of a plurality of sync blocks in a predetermined time period.
When variable length data of each macro block is packed, fixed portions (equivalent to data areas for sync blocks) corresponding to the number of macro blocks in a predetermined time period (for one frame as an edit unit) of which the data amount is selected are prepared. One varia
Miyazawa Satoshi
Suzuki Takao
Togashi Haruo
Boccio Vincent
Frommer William S.
Frommer & Lawrence & Haug LLP
Simon Darren M.
Sony Corporation
LandOfFree
VIDEO DATA RECORDING APPARATUS, VIDEO DATA RECORDING 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 VIDEO DATA RECORDING APPARATUS, VIDEO DATA RECORDING METHOD,..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and VIDEO DATA RECORDING APPARATUS, VIDEO DATA RECORDING METHOD,... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3139180