JP3485693B2 - Video data recording method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of recording video data in which a video signal is digitized on a tape, and more particularly to a video data recording method which enables special reproduction.

[0002]

2. Description of the Related Art In the ATV (Advanced Television) standard proposed as a next-generation digital broadcasting system in the United States, MPEG (Moving Picture Image) which is an international standard for image compression is used as a compression method when transmitting image data.
Coding Experts Group) method is about to be adopted. In addition, DVB (Digital Video)
Broadcasting) will also use MPEG.

The MPEG system employs motion-compensated prediction, DCT (discrete cosine transform), and variable length coding in data coding. As shown in the frame structure of FIG. Depending on the prediction mode, I (intra-c
oded) picture, P (predictive coded) picture, B (bi
-directionally predictive coded) pictures are classified into three types. The I picture is an intra-frame coded image, the P picture is an inter-frame predictive coded image predicted from a temporally preceding frame, and the B picture is an inter-frame predictive coded image from preceding and following frames.

FIG. 8 shows a data hierarchical structure of an image in the MPEG system. It is configured as follows from the lower layer. (Block layer) Blocks are 8x adjacent to each other in luminance or color difference.
It consists of 8 pixels, and DCT is executed in this unit. (Macroblock Layer) A macroblock is composed of four adjacent luminance blocks and two chrominance blocks Cb and Cr at the same position on the screen, for a total of six blocks. (Slice Layer) A slice is composed of a plurality of macroblocks that are continuous in the scanning order of an image. (Picture layer) A picture consists of multiple slices,
Form one image. It is classified into the above-mentioned I picture, P picture, and B picture depending on the encoding format. (GOP Layer) A GOP (Group of Pictures) is composed of one or a plurality of I pictures and 0 or a plurality of non-I pictures. (Video Sequence Layer) A video sequence is composed of one or a plurality of GOPs having the same image size and image rate.

On the other hand, HD (High Definition) digital V
The CR Council is studying the standardization of a digital VTR that records and reproduces video signals as digital data. Here, it is conceivable to record the ATV standard data (ATV signal) compressed by the above-mentioned MPEG method or the DVB signal on the magnetic tape.
FIG. 9 shows a standard signal recording format in a digital VTR. As shown in the figure, the track formed on the signal surface of the magnetic tape (21) is composed of an ITI area including insert data and track information, an audio data area, a video data area, and a subcode data area. In the PAL mode, 360 tracks are recorded on the magnetic tape per second, and an average of 1 frame image is 1
It is recorded using two tracks.

Data is recorded in units called sync blocks, and 135 data is recorded in a video data area of one track.
Sync blocks can be recorded. As shown in FIG. 10, each sync block has a sync data area (2 bytes), an ID data area (3 bytes), and a video data area.
(77 bytes) and parity area (8 bytes) for a total of 90
Composed of bytes.

When recording MPEG data in the above-mentioned video data area, paying attention to the macro block unit in which the input MPEG bit stream is recorded in the data hierarchy shown in FIG. 8, the code length of this macro block is not constant. Since it is recorded without being mixed with the upper layer,
There is no fixed relationship between the sync block and the recorded macro block. That is, the position on the screen determined by the macro block and the position on the recording track pattern determined by the sync block are irrelevant.

When the magnetic tape recorded in this way is run at a speed different from that at the time of recording to perform special reproduction such as high-speed reproduction, the head scans across a plurality of tracks, and therefore the MPEG system is used. The data of is not obtained continuously and becomes fragmentary. As described above, since P pictures and B pictures in the MPEG bit stream are inter-frame predictive coded images, even if they are acquired in pieces, the images cannot be reconstructed.

That is, the special reproduction picture can be reconstructed based only on the I picture which is the intra-frame predictive coded picture, and in the reconstruction of the I picture, the I picture distributed on the track can be reconstructed. You need to get all the data in order. Therefore, special reproduction cannot be performed by a method of sequentially recording the input MPEG bit stream as it is.

Therefore, as a special reproduction method in the digital VTR, the journal "Intern" issued in October 1993 was published.
“A Recording Metho” from “ational Workshop On HDTV '93”
d of ATV data on a Consumer Digital VCR ”is known.

In this method, a specific area is provided in the video data area of each track, and the I picture data is recorded as the special reproduction data in the specific area in addition to the normal reproduction data. . The reason why such a recording method is possible is that the data rate of the ATV signal is about 19.3 Mbps, while the HD digital VC is
This is because the one-track video data area based on the standards of the R Council can be recorded at a data rate of about 24.9 Mbps, so that an area corresponding to about 5.6 Mbps remains as a recordable area. This surplus area is
This corresponds to about 32 SB for the video data area 135 SB (sync block) of one track.

Specifically, as shown in FIG. 11, a data area NPA for normal reproduction is provided in the video data area on one track, and the front, center and rear areas on the track are divided into three areas. Data area TP for special playback
A is provided. A total of 32 SB of the video data area 135SB of one track is allocated to the three special reproduction data areas TPA.

In this case, trick play data is assigned by the method shown in FIG. First, macroblocks A, B, C, ... Of an I picture are extracted from the MPEG bit stream as shown in FIG. 9A, and data strings A ′, B ′, C ′, and so on are extracted as shown in FIG. Get ... here,
The code lengths of the encoded macroblocks are different. Then, as shown in FIG. 7C, the data strings A ′, B ′,
C ′, ... In order of sync blocks SB1, SB2, S
Allocate to B3, ... At this time, since the sync block has a constant code length, there is no fixed relationship between each sync block and the assigned macro block, and one macro block extends over a plurality of sync blocks.

Then, the same special reproduction data is recorded on the same number of tracks as the maximum double speed number n set in special reproduction. For example, when n = 5, the same data is recorded in the special reproduction data area TPA of five consecutive tracks as shown in FIG.

Further, the data is updated in units of 5 tracks, and this is repeated a plurality of times (m times) to record all the I picture data by 5 × m tracks.
According to the above-mentioned recording method, if the reproduction speed is 5 times or less, 5 × m tracks will be recorded once every 5 tracks for a total of m.
By scanning twice, it is possible to acquire all the video data of the I picture.

[0016]

By the way, in DVB (Digital Video Broadcasting) to be adopted in Europe, the bit rate of a broadcast signal of one program is, for example, 2
It will be variably set to an arbitrary value such as 0 Mbps, 10 Mbps, and 4 Mbps. On the other hand, digital VTR
In, it is possible to record a signal with a bit rate of 25 Mbps. Therefore, DVB signal (normal playback data)
If the DVB signal is less than 19.3 Mbps, if the DVB signal is recorded as it is on the magnetic tape by the digital VTR, a no-signal area having a width corresponding to the amount of decrease in the bit rate is generated. There is a problem in effective use of.

An object of the present invention is to provide a video data recording method capable of effectively utilizing a tape even when the bit rate of normal reproduction data is lowered.

[0018]

In the video data recording method according to the present invention, when recording video data on a tape by a signal recording head, one or a plurality of tracks are recorded as one track.
As a block, each of one or a plurality of tracks included in each block has a first area in which normal reproduction data is recorded and a second area in which special reproduction data is recorded.
The first area is reduced and the second area is enlarged as the bit rate of the data for normal reproduction decreases while the track is arranged in the track longitudinal direction.

That is, when the bit rate of the normal reproduction data decreases, the size of the first area necessary for recording the normal reproduction data decreases according to the amount of decrease, so that the second area is reduced accordingly. It expands. The data area for special reproduction needs to be arranged at a limited position where head trace during special reproduction can be performed, and although the amount of data is limited, due to the expansion of the second area, Tracking control for the reproduction data area becomes easy. or,
The image quality can be improved by increasing the data amount of special reproduction data.

Specifically, when the second area is expanded, the second area formed when the bit rate of the normal reproduction data is maximum is used as the basic area, and the second area is set as an area in which head tracing during special reproduction is possible. Add 2 areas. In this case, the head trace passing through the basic area of the second area during special reproduction passes through the additional area in the middle thereof, and data is reproduced from both the basic area and the additional area.

More specifically, the second area is added in order from an area where tracking control is easily performed during special reproduction, or an area in which data is likely to be reliably reproduced during special reproduction. Can be adopted.

If the same image data as that of the basic area is recorded in the additional area, even if the head trace that should pass through the basic area in the second area is slightly displaced, the additional area will be recorded. The data will be reliably reproduced from.

On the other hand, special reproduction data includes main data (I picture data) necessary for special reproduction and auxiliary data (for example, I of different frames) that should contribute to image quality improvement.
Picture data), the main data is recorded in the basic area and the auxiliary data is recorded in the additional area in the second area formed in the fixed tape section.
The image quality can be improved by reproducing both data.

[0024]

According to the video data recording method of the present invention, even if the bit rate of the normal reproduction data is lowered, the tape can be effectively used by facilitating the tracking control or improving the image quality.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION In the following, data of the DVB standard will be recorded in HD.
An example of recording by a digital VTR based on the standards of the Digital VCR Council will be described in detail with reference to the drawings. However, since the DVB standard has not been finalized, the data of the ATV standard will be described as an example.

First, FIG. 4 shows a structure of a recording track which is a premise of the present invention. The head is composed of two 180 ° facing type heads, and a high-speed special reproduction data area TH for realizing special reproduction by high-speed feed (for example, 18 times speed reproduction) and special reproduction by low-speed feed for the video data area 135SB. A low speed special reproduction data area TL for realizing (for example, 4 × speed reproduction) is formed. still,
Each track is classified into an f0 track, an f1 track and an f2 track according to the type of pilot signal for tracking, and these tracks are repeatedly formed in the order of f0 → f1 → f0 → f2 as shown in the figure.

Specifically, for the f0 track, S
B40-44, SB62-66, SB84-88, SB
106-110, SB128-132, and SB150
Data area TH for high-speed special playback in 6 areas up to 154
Is provided. SB116 to f1 track
A low speed special reproduction data area TL is arranged in the area 155. And other areas of the f0 and f1 tracks,
The entire video data area of the f2 track is used as the normal reproduction data area NA.

The special reproduction data is assigned to each area by the method shown in FIG. First, the same figure
The macroblocks A, B, C, ... Of the I picture are extracted from the MPEG bit stream as shown in (a), and the data strings A ′, B ′, C ′, ... Are extracted as shown in FIG. obtain. Here, the code lengths of the encoded macroblocks are different. Then, as shown in FIG. 9C, the data blocks A ′, B ′, C ′, ...
1, SB2, SB3, ... Then, the same special reproduction data is repeatedly recorded on the same number of tracks as the double speed number n. For example, when n = 4, the same data is recorded in the special reproduction data area in the same unit with four continuous tracks as one unit.

Further, the data is updated in units of 4 tracks, and this is repeated a plurality of times (m times), and all the video data of the I picture is recorded by (4 × m) tracks. According to the above-described recording method, if the reproduction speed is 4 times or less, (4 × m) tracks are scanned once every four tracks, for a total of m times, to obtain all video data of I pictures. You can

In this embodiment, a DV having a variable bit rate is used.
A recording area for low-speed special reproduction data is added to the B signal by using the low-speed special reproduction data area TL shown in FIG. 4 as a basic area. FIG. 1 shows an add-on area when quadruple speed reproduction is realized by two 180 ° facing type heads. That is, SB45 to 61, SB67 to 83, and SB89 for the f0 track before the f1 track.
To 105 and SB111 to 115, the low speed trick play data area TA can be added. For the f1 track, a low-speed special reproduction data area TA can be added in the area of SB99 to 115. Further, a low-speed special reproduction data area TA can be added to the area of SB31 to 54 on the f2 track.

The additional area TA shown in FIG. 1 is obtained by computer simulation as an area in which the signal can be reproduced by the head trace when the effective trace rate is 50%. Where the effective trace rate is 5
0% means that when a region of 50% or more of the track width is traced by the magnetic head, the recording signal of the region can be read.

Further, in the present embodiment, in response to the bit rate of the DVB signal being variably set, when the low-speed special reproduction data area is expanded in accordance with the decrease in the bit rate, the expansion area is set to the above-mentioned expansion area. Then, the priority order was set about which area part should be prioritized. When setting the priority order, the effective trace rate is 50% to 60%, 70
In view of the fact that the readable area decreases as the percentage increases, a higher priority is set for the area that can be read even if the effective trace rate increases.

FIGS. 2 and 3 show the priorities assigned to the additional area TA. Here, the relationship between the bit rate of the DVB signal and the extension area (priority order) is set as follows. (Bit rate) (Additional area) 16.863 to 17.787 Mbps ... 15.246 to 16.863 Mbps ..., 14.553 to 15.246 Mbps ..., 9.600 to 145553 Mbps ...

As shown in FIG. 1, the low-speed special reproduction data area TL, which is the basic area, is provided on every third track, and is the same for two low-speed special reproduction data areas TL across eight tracks. Data is recorded and updated every 8 tracks. And do this multiple times
Repeat (m times) by (8 × m) tracks, I
All video data of a picture is recorded.

On the other hand, for the data to be recorded in the extension area TA, the following two modes are switched and set. That is, in the first special reproduction mode, the same data as the basic area TL is recorded in the extension area TA according to the above-mentioned priority order. In this case, the image quality of the special reproduction video does not change, but tracking control becomes easier as the extension area is expanded.

Further, in the second special reproduction mode, the frames different from the basic area TL according to the above-mentioned priority order.
The special reproduction data of (I picture) is recorded in the extension area TA. In this case, the value of m described above may be small, and as a result, the image update rate at the time of special reproduction is high, and high-quality special reproduction video can be obtained.

FIG. 5 shows a signal recording circuit in a digital VTR for carrying out the video data recording method of the present invention. First, the MPEG bit stream based on the DVB standard is input to the first buffer memory (1), the I picture extracting circuit (2) and the bit rate check circuit (4). The first buffer memory (1) performs signal processing for allocating the input bit stream to the normal reproduction data area of each sync block, and mixes the normal reproduction sync block data obtained by the signal processing. ).

On the other hand, the I picture extracting circuit (2) extracts only the I picture from the input bit stream and supplies it to the second buffer memory (5). The second buffer memory (5) performs signal processing for allocating the input data to the trick play data area of each sync block, and the trick play sync block data obtained thereby is supplied to the mixing circuit (3). To be done.

At the same time, the bit rate check circuit (4)
Checks its bit rate based on the input bit stream and supplies the result to the mixing circuit (3). The selection signal of the above-mentioned first special reproduction mode / second special reproduction mode is inputted to the mixing circuit (3). The mixing circuit (3) determines, according to the bit rate, to which priority order the extension area should be provided, and also determines the data to be recorded in the extension area according to the mode selection signal, as shown in FIG. A switching operation is performed to realize the recording patterns in the priority order shown in FIG. The mixed data of the normal reproduction data and the special reproduction data thus obtained is supplied to the error correction code adding circuit (7). When a header representing the maximum bit rate is added to the input bit stream, the bit rate check circuit (4) can be replaced with a header decoding circuit.

In the error correction code adding circuit (7), the mixing circuit
After the error correction code is added to the output of (3), the sync data and the ID data are added by the first data adding circuit (8). Further, in the second data adding circuit (9) in the subsequent stage,
I, audio data, and subcode are added to form data of a predetermined format shown in FIGS. 9 and 10, and this data is recorded on the tape by the magnetic head.
The error correction code adding circuit (7) includes a memory control circuit (1
RAM (10) controlled by 1) is connected and R
The error correction code is read from the AM (10) and supplied to the error correction code adding circuit (7). The operation timing of the additional circuit (8) and the memory control circuit (11) is controlled by the timing circuit (6).

FIG. 6 shows the configuration of the signal reproducing circuit of the digital VTR. First, the signal reproduced from the tape by the magnetic head is separated into ITI, audio data and sub-code by the first separation circuit (12), and then further sync data by the second separation circuit (13) in the subsequent stage. And the ID data are separated. The video data thus obtained is subjected to known error correction in the error correction circuit (14). The data after error correction is the normal reproduction data N in the third separation circuit (15).
It is separated into P and special reproduction data TP. The normal reproduction data NP is converted into a constant rate by the first buffer memory (16) and input to the selector (17).

On the other hand, the trick play data TP passes through the second buffer memory (18) and then the MPEG formatting circuit (19).
Is supplied to. In the MPEG formatting circuit (19),
A layer above the macroblock is added to the trick play data to form a bitstream that can be decoded by an MPEG decoder (not shown), and the bitstream is sent to the second buffer memory (20) at the next stage.

The bit stream is constant-rated in the second buffer memory (20) and supplied to the selector (17). The selector (17) selects the input data according to the mode signal NP / TP for switching between the normal reproduction and the special reproduction, and outputs it as an MPEG bit stream to the television receiver. As a result, the normal reproduction image or the special reproduction image is displayed on the screen of the television receiver.

According to the above digital VTR, when the bit rate of the original DVB signal (MPEG bit stream) to be recorded on the tape is reduced, the special reproduction data area is expanded according to the reduction amount. Image quality can be improved by facilitating tracking control or improving the image update rate.

The above description of the embodiments is for explaining the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope.
Further, it goes without saying that the configuration of each part of the present invention is not limited to the above-described embodiment, and various modifications can be made within the technical scope described in the claims.

[Brief description of drawings]

FIG. 1 is a diagram showing a signal recording pattern according to a video data recording method of the present invention.

FIG. 2 is a diagram in which priorities of extension areas are entered in a trick play data area of each track.

FIG. 3 is a diagram showing a correspondence relationship between priorities and additional areas of special reproduction data areas.

FIG. 4 is a diagram showing a signal recording pattern which is a basis of the video data recording method of the present invention.

FIG. 5 is a block diagram showing a configuration of a signal recording circuit.

FIG. 6 is a block diagram showing a configuration of a signal reproduction circuit.

FIG. 7 is a diagram showing a frame structure of an MPEG system.

FIG. 8 is a diagram showing a data hierarchical structure in the MPEG system.

FIG. 9 is a diagram showing a signal recording format on a track in a digital VTR.

FIG. 10 is an explanatory diagram showing a data structure of a sync block in a digital VTR.

FIG. 11 is a diagram showing a signal recording pattern according to a conventional video data recording method.

FIG. 12 is an explanatory diagram showing a method of allocating special reproduction data.

[Explanation of symbols]

NA Normal playback data area TH High-speed special playback data area TL Low-speed special playback data area TA expansion area

─────────────────────────────────────────────────── --- Continuation of front page (72) Inventor Masahiko Nishikawa 2-5-5 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. (56) Reference JP-A-8-163504 (JP, A) JP Flat 8-32926 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 5/76-5/956 G11B 20/10-20/12

Claims (2)

(57) [Claims] 1. When a plurality of tracks are repeatedly formed on a tape by a signal recording head and a series of digital video data is recorded on these tracks, one or a plurality of tracks are set as one block and each block is recorded. In the video data recording method, the first area in which the normal reproduction data is recorded and the second area in which the special reproduction data is recorded are arranged in the track longitudinal direction on each of one or more tracks included in And the bit rate of normal playback data
The first area shrinks as
Formed when the bit rate of the playback data is maximum
Head trace during special playback with the second area as the basic area
Video data recording method to add a second area to the available area
Therefore, the special playback data is the main data required for special playback.
Data and auxiliary data that should contribute to image quality improvement.
Of the second area formed within a certain tape section, the foundation
Main data is recorded in the area, while auxiliary data is recorded in the extension area.
A video data recording method characterized by recording data. 2. A signal recording head is used to copy data onto a tape.
Repeatedly forming several tracks to create these tracks
When recording a series of digital video data on the
Included in each block with several tracks as one block
Each of the one or more tracks that are
Data area for normal playback in which
Multiple types of special playback data recorded with special playback data
Video data that arranges the data area in the longitudinal direction of the track
In the recording method, the bit rate of the normal playback data is
Normal playback data area shrinks as it decreases
And when the bit rate of the data for normal playback is the maximum
The special playback data area formed on the
Video data recording method to expand special playback data area
The special playback data area is used for other types of special
Characterized by expansion in the area excluding the playback data area
And video data recording method.