KR100200577B1 - Method for recording image data for trick play - Google Patents

Abstract

The present invention relates to a method for recording video data for trick play in recording an ATV (Advanced Television) or DVB (Digital Videl Broadcasting) signal on a digital video tape, wherein the four consecutive tracks of the digital video tape are united. A track classification step of dividing the track into a first track, a second track, a third track, and a fourth track sequentially; The first track and the third track divided in the track division step are divided into groups of one or more sync blocks as one group, and normal data is recorded in the odd odd group and the even group A video data recording step on first and third tracks for recording trick data, respectively; In the track classification step, the divided second track is divided into three groups comprising one or more sync blocks as one group, and the normal data is recorded in the odd odd group and the trick data in the even group. Recording image data on a second track for recording the respective tracks; The fourth track divided in the track classification step includes a video data recording step on the fourth track that records only normal data. Therefore, cost reduction is achieved by adding and recording an error correction code for error correction of the trick data and not adding a separate decoder therefor.

Description

Video data recording method for trick play

1 is a diagram showing a track format of a digital video tape having a recording format of an SD-VCR.

2 is a diagram illustrating a typical data sink block.

3 is a diagram showing only video sectors in one track.

4 is a layout structure of trick data recorded in one track amount according to the present invention.

5 is a diagram showing an embodiment in which normal data and trick data are mixed and recorded on a magnetic tape according to the present invention.

The present invention relates to a digital video cassette recorder, and more particularly, to a method of recording video data for trick play in recording an ATV (Advancde Television) or DVB (Digital Videl Broadcasting) signal on a digital video tape.

Currently, the signal recording formats of ATV and DVB video cassette recorders basically use the SD-VCR recording format, which is agreed upon at corporate meetings. Accordingly, development of a digital video tape recorder (hereinafter referred to as DVCR) that records and plays back an ATV or DVB signal on a digital video tape of an SD-VCR (Standard Definition Video Cassette Recorder) is in progress. How to arrange data for trick play for slow etc.

The underlying technical principle for recording trick data for baby trick play on digital videotape is that the bitstream of the SD-VCR is 24.9 Mbps (Mega bits per second), and the bits of the ATV and DVB signals. This is due to the stream being 19.3 Mbps. As a result, a recording area corresponding to 5.6 Mbps remains. In any way, recording trick data for performing trick play in the extra area, that is, the extra video sector area, can satisfy various trick play speeds, satisfy various types of scanners, and solve image quality and noise problems. Research is underway on whether it can be improved.

One approach to trick data recording for trick play is to place the trick play data on the trajectory of the recording medium that the head scans in response to each trick play speed. This method has excellent image quality of the trick play screen, but requires precise servo control such as speed lock, pager lock, and track select to accurately scan the trajectory of the head where the data for trick play is precisely arranged according to each speed. There is a problem that the cost is increased due to the burden of hardware design.

Also, ATV and DVB signals are signals vulnerable to MPEG2 and are vulnerable to errors. This is due to performing signal processing in units of 1 GOP (Grpup of Picure). The ATV and DVB signals are based on MPEG2 signals, which are intercoded bitstreams with 1 picture (Intra picrure), p picture (Predictive picture) and B picture (Bidirectional Predictive picture). It is composed. I pictures are intra coded, p pictures are inter coded using pictures of the past, and B pictures are inter coded using pictures of the past and the future. That is, since the I picture is independent but the P picture and the B picture are dependent on the I picture, when an error occurs, the picture in 1 GOP unit continuously generates an error. In other words, since the pictures that make up 1GOP are correlated, if an error occurs in one picture, the effect also affects the other picture. Thus, a description of error correction must be involved. Therefore, an error correction code (ECC) is recorded in a predetermined recording area for error correction of normal data. In addition, the error does not occur only in normal data, but may occur in trick data. Therefore, the recording of the error correction code is also required in the signal processing of the trick data for trick play. Therefore, there is a problem of cost increase because a separate decoder for interpretation of an error correction code recorded for error correction of trick data has to be added.

That is, the prior art for trick play has a problem of a cost increase due to the need for accurate servo control and the addition of a decoder that needs to interpret an error correction code for error correction of trick data.

Accordingly, the first object of the present invention is to solve the problems of the prior art as described above, and does not require the accuracy of the servo control in the head scanning the trick data, and also the ratio of the servo control. The present invention provides an image data recording method that does not deteriorate image quality despite an accurate scan, resulting in technical improvement due to cost reduction.

In addition, the second object of the present invention is to record image data that allows the error correction code of the trick data to be interpreted with the decoder used for error correction of normal data without separately adding a decoder to be used for error correction of the trick data. In providing a method.

The present invention for achieving the above-mentioned first and second purposes is to record ATV and DVB signals including normal and trick data, which are supplied at predetermined intervals and independently decodable, and are recorded on a digital video tape. A video data recording method comprising: a track classification step of sequentially dividing four consecutive tracks of the digital video tape into a first track, a second track, a third track, and a fourth track; The first track and the third track divided in the track classification step are divided into n groups including one or more sync blocks as one group, and the normal data is divided into the odd odd groups. Recording the video data on the first and third tracks for recording the trick data in the even group; The second track divided in the track classification step is divided into three groups comprising one or more sync blocks as one group. The group includes an image data recording step on a second track for recording trick data respectively;

The fourth track divided in the track classification step includes a video data recording step on a fourth track that records only normal data.

Preferably, the n groups distinguished in the image data recording step on the first and third tracks consist of eleven first and third tracks, respectively.

In the image data recording step on the first and third tracks, the trick data recording area divided into five groups is divided into five groups consisting of five sync blocks in 30 sync blocks. It is preferable to construct.

Hereinafter, with reference to the accompanying drawings will be described the present invention in more detail.

1 is a diagram showing a track format of a digital video tape having a recording format of an SD-VCR. In FIG. 1, tracks are divided in the order of the ITI (Insert and Track Inrormation) sector 2, the audio sector 4, the video sector 6, and the subcode sector 8 from the couple at which the head starts to scan. Gaps G1, G2, and G3 exist between the sectors. The ITI sector 2 includes an ITI Pre-Amble region 10, a Start-Syncblock region 12, a Track Information region 14, and an ITI Postamble ( ITI Post-Amble) region 16. The audio sector 4 has an audio preamble area 18, fourteen audio data sync blocks 20, and an audio post-amble area 22. The video sector 6 has a video preamble area 24, 149 video data sync blocks 26, and a video post-amble area 28. The subcode sector 8 has a subcode preamble area 30, a subcode area 32 and a subcode postamble area 34. The area after the subcode sector 8 is an overwrite margin 36.

2 is a diagram illustrating a typical data sink block. In Fig. 2, reference numeral 38 denotes a sync area having a recording area of 2 bytes, 40 denotes an ID code having a recording area of 3 bytes, and 42 denotes a recording area of 77 bytes. 44 is inner parity having an 8-byte recording area.

3 is a diagram showing only video sectors in one track.

In Fig. 3, reference numeral i on the left indicates the sync block number of the video sector as the sync block number. It can be seen that the video sector allocates sync blocks from sync block 19 to sync block 167. Reference numeral 100 is an area where video data is recorded, 102A and 102B are areas where video auxiliary data is recorded, 104 is a sync area, 106 is an area where an ID code is recorded, and 108 is an inner parity. An area for performing internal call error correction is recorded and 110 is an area for performing outer code error correction by recording an outer parity. In each sync block, the sink area 104 is allocated to a memory capacity of 2 bytes, and the ID code 106 is assigned to a memory capacity of 3 bytes, and the video auxiliary data areas 102A and 102B and the video data area 100 are allocated. ) And outer parity 110 are allocated to a memory capacity of 77 bytes, and inner parity 108 is allocated to a memory capacity of 8 bytes. In addition, the outer parity 110 is allocated to 11 sync blocks in one track. The speed of trick play has a speed other than normal play. At this time, the image quality when the trick play is in progress may be relatively lower than the normal play. This is because in trick play, only the outline of the screen is shown, but the function can be performed.

In the video data being recorded on the recording medium, the trick data for performing the trick play is recorded at a designated position separate from the normal data for performing the normal play. At this time, the trick data is used to extract only a part of the normal data. For this reason, the quality of the trick play is relatively lower than that of normal play. The reason for the deterioration in image quality is that the data extracted for use as the trick data is composed of data of one frequency or low frequency component of one pixel. Therefore, since the trick data uses only one picture or a part of one picture, the recording capacity required per unit picture of the trick data and normal data is naturally different. For example, if normal data having a recording capacity of 12 tracks can implement one picture, the trick data required to implement the same picture can be implemented with a recording capacity of 12 tracks or less. In practice, the recording capacity of trick data versus normal data required to implement the same picture is far less than that of normal data.

4 is a layout structure of trick data recorded in one track amount according to the present invention.

The data recorded in Fig. 4 is trick data. 4 is shown except for the sink area 104 of FIG. 3 and the area 106 where the ID code is recorded. In FIG. 4, the area 400 in which trick data is recorded is composed of 135 sync blocks, and the areas 402a and 402b in which video auxiliary data is recorded are divided into two areas. In other words, as shown in FIG. 4, the video sub data allocated to one sync block is recorded in an area 402a, and the video auxiliary data allocated to two sync blocks is recorded in an area 402b. Thus, areas 400, 402a and 402b in which video data and video assistance data are recorded are allocated to 138 sync blocks. In addition, the area 404 in which the outer parity is recorded is allocated to 11 sync blocks. In FIG. 4, an area 404 in which inner parity is recorded is allocated to 11 sync blocks. Although not shown in FIG. 4, the area where inner parity is recorded, occupies an 8-byte recording area after each sync block. In the trick data encoding, the video auxiliary data area is filled with '0' or predetermined pattern data and error correction is performed to allocate the outer parity to 11 sync blocks. When recording to tape, 138 sync blocks are recorded in 5 sync blocks except 3 sync blocks, which are areas of video auxiliary data, and outer parity is 4 sync blocks, which are dummy sync blocks, in 11 sync blocks. In addition, all are recorded in 15 sync blocks. In addition, 15 sync blocks are recorded in units of 5 sync blocks.

The data of MPEG2 is transmitted in a packet unit on a transport layer. Each packet is 188 bytes and maps two packets of 187 bytes except for one sync to 5 sync blocks. In the extra area, control signals such as time stamp, normal data, trick data, dummy data, flags, and ID are added to the front of each packet. .

As a result, according to the present invention, as shown in FIG. 4, in order to perform a trick play, the trick data and the normal data resulting from error correction of the trick data in the normal ECC structure are distributed to a plurality of tracks in a predetermined form to normal data. It is mixed with and recorded.

Next, an aspect in which the trick data is mixed with the normal data will be described based on the technical idea of the present invention.

5 is a diagram showing an embodiment in which normal data and trick data are mixed and recorded on a magnetic tape according to the present invention.

The track data of track 0 and track 2 is recorded at a specific speed, and track 1 is recorded at a speed lower than the speed specified above.

The magnetic tape consists of a plurality of tracks. Referring to FIG. 5, track 0, track 1, track 2, and track 3 are continuously repeated in one unit. Track 0 and track 2 have the same form in terms of trick data being recorded. The trick data area of track 0 is repeated k (k0) times in track 0 and track 2 in the horizontal direction.

That is, the track 0 and the track 2 are viewed horizontally in the drawing, that is, the trick data recorded in sync blocks of the same number are data generated in the same image. Of course, vertically different data. The area is divided to describe the form in which the trick data and normal data of track 0 and track 2 are recorded. Then, track 0 will be described first.

Normal data is recorded in an area 500 allocated to a predetermined number of sync blocks. Trick data is recorded in an area 502 allocated to five sync blocks. Normal data is recorded in an area 504 allocated to a predetermined number of sync blocks. Trick data is recorded in the area 506 allocated to the five sync blocks. Normal data is recorded in an area 508 allocated to a predetermined number of sync blocks. Trick data is recorded in an area 510 allocated to five sync blocks. Normal data is recorded in an area 512 allocated to a predetermined number of sync blocks. Trick data is recorded in an area 514 allocated to five sync blocks. Normal data is recorded in an area 516 allocated to a predetermined number of sync blocks. Trick data is recorded in the area 518 allocated to the five sync blocks. Normal data is recorded in an area 520 allocated to a predetermined number of sync blocks.

Track 1 is explained.

Normal data is recorded in an area 522 allocated to a predetermined number of sync blocks. Trick data is recorded in the area 524 allocated to 25 sync blocks. Normal data is recorded in an area 526 allocated to a predetermined number of sync blocks.

Track 2 is explained.

In the area 528 corresponding to a predetermined number of sync blocks, normal data is recorded. Trick data is recorded in an area 530 allocated to five sync blocks. Normal data is recorded in an area 532 allocated to a predetermined number of sync blocks. Trick data is recorded in an area 534 allocated to five sync blocks. Normal data is recorded in an area 536 allocated to a predetermined number of sync blocks. Trick data is recorded in an area 538 allocated to five sync blocks. Normal data is recorded in an area 540 allocated to a predetermined number of sync blocks. Trick data is recorded in an area 542 allocated to five sync blocks. Normal data is recorded in an area 544 in which a predetermined number is allocated to the sync block. Trick data is recorded in an area 546 allocated to five sync blocks. Normal data is recorded in an area 548 allocated to a predetermined number of sync blocks.

Track 3 is explained.

In all areas 550, only normal data is recorded.

4 and 5, the trick data of FIG. 4 is distributed and recorded like the hatched portion of FIG. Of course, the outer parity and inner parity for error correction of FIG. 4 are also recorded in the area where the trick data hatched in FIG. 5 is recorded. In FIG. 4, the trick data is recorded in 135 sync blocks. That is, in FIG. 5, five sync block groups composed of five sync blocks are separated from each other, as recorded in track 0 and track 2, and five sync blocks as recorded in track 1. Five sync block groups consisting of a group of one is located in one sink block group consisting of 25 sync blocks. Therefore, the trick data occupying the area of 135 sync blocks is composed of 27 groups, and the outer parity for error correction of the trick data occupying the recording area of 11 sync blocks is composed of 3 groups. Here, since only 11 sync blocks are required for the outer parity, 4 sync blocks write data '0'.

In the video data recording method as described above, an RS ECC structure encoder is recorded by recording an error correction code for correcting trick data by adding a small hardware using a normal data error correction structure and not adding a separate decoder therefor. It is very simple and the decoder is very complicated, so it can improve the error correction rate of trick data with little additional cost.

Claims (3)

A video data recording method in which ATV and DVB signals including picture data supplied at predetermined intervals and independently decodable are divided into normal data and trick data and recorded on an SD digital video tape. A track classification step of sequentially dividing the first track, the second track, the third track, and the fourth track by using four tracks as a unit; The first track and the third track divided in the track classification step are divided into groups of one or more sync blocks into one group, and normal data is recorded in the divided odd group. And in the even-numbered group, video data recording steps on first and third tracks respectively recording trick data; Recording image data on the second track; A video data recording method comprising a video data recording step on a fourth track which records only normal data in the fourth track divided in the track classification step; The video data recording method as claimed in claim 1, wherein the group of n divided in the video data recording step on the first and third tracks comprises 11 first and third tracks. The trick data recording area according to claim 2, wherein the trick data recording area divided into five groups is composed of eleven groups in the image data recording step on the first and third tracks, from thirty sync blocks to five sync blocks. An image data recording method comprising five groups.