Motion video signal processing for recording or reproducing – Local trick play processing – With randomly accessible medium
Reexamination Certificate
1998-11-05
2001-02-20
Nguyen, Huy (Department: 2615)
Motion video signal processing for recording or reproducing
Local trick play processing
With randomly accessible medium
C386S349000
Reexamination Certificate
active
06192186
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for reproducing or providing MPEG data.
PRIOR ART
In these years, a Digital VCR, in which a video signal is recorded and reproduced as a digital data, has been developing. The digital VCR may record a video signal, such as, from television broadcasting, encoded to MPEG format which is an International standard for a method of compressing pictures. As to a recording media, not only a tape media but also a disk media are used for a recording and reproducing apparatus. It is noted that the present invention is applicable to both type of recording media, such as, disk or tape media.
MPEG method adapted a motion compensate prediction technology, a DCT (discrete cosine transform) technology and an entropy coding method. There are three types of frame picture in MPEG method, such as, I picture, P picture and B picture, which are categorized on different prediction method in time as shown in
FIG. 4. I
picture is an intra-coded picture and a complete one flame picture can be re-constructed only from I picture data. P picture is an inter frame predictive coded picture which is predicted from P or I picture located previously in time. B picture is also an inter frame predictive corded picture predicted from I or P picture placed previously or postly in time. Accordingly, a picture corresponding to P or B picture can not be re-constructed from only P or B picture data; other frame data for the prediction is also necessary for re-construction of that picture.
Further, the amount of data for each picture is not a fixed value, then there is no fixed relation between the location on the tape and the location on each picture. In the case of pictures having a frame rate of 30 frame per second, the data of 30 frame per second on average is necessary for collective I, P and B picture.
In the following description, it is the case that the MPEG data having 30 frame per second is recorded into a digital VCR (hereinafter, DVCR) in accordance with the standard of digital VCR association.
First of all, DVCR format will be described briefly.
FIG. 5
is a schematic diagram of recording format on a magnetic tape in accordance with the standard.
The amount of data recorded per second is corresponding to the data amount of 300 tracks. Each track has an ITI (Insert and Track Information) area, an Audio area, a Video area and sub-code area recorded in this turn.
FIG. 6
is a schematic diagram of the format in the Video area.
Data of the Video area comprises a block including 77 bytes×138 bytes which include 135 bytes for picture data and 3 bytes for auxiliary data (VAUX). An ECC
2
Parity (11 bytes) is first added in the direction of 138 byte, then an ECCI parity (8 bytes) is added in the direction of 77 bytes. The data of 149 sync blocks is recorded on the media.
Audio(Sound), Video(Picture) and other data is respectively recorded as a unit of sync block. The sync block, as shown in
FIG. 7
, consists of a sync area (2 bytes), an ID area (3 bytes), a data area (77 bytes) and a parity area (8 bytes) and contains 90 bytes in total.
MPEG data, however, is recorded only into the Video data area of DVCR format. There are 135 sync block areas in the Video data area. As shown in
FIG. 8
, the Video data area contains a data area for normal play (NP data area), a data area for special play(TP data area) and, for option, a data area for error correction of MPEG signal recording (ECC
3
area). Further, the TP data area contains a TPH data area and a TPL data area in accordance with the tape speed of special play.
A method of slow motion play will be described. In normal play mode, as shown in FIG.
3
(
a
), a magnetic head runs along recorded track on the magnetic tape. If the speed of the tape is slower than normal, the magnetic head runs with some angle with recorded tracks as shown in
FIG. 3
(b). Accordingly, one scan of head can not reproduce all the data from one track completely.
It, however, is well known that, if a head width and a tape speed are defined appropriately in accordance with a track width, all of data in one track can be reproduced as a result of several times of scan. This data reproduced from several scans of one track is stored in a memory and combined then all data of one track can be reproduced.
For example, if tape speed is set at one-third of normal play, three scans of head may reproduce all the data of one track. Therefore, all of data is reproduced at one-third of normal play for tape speed.
As described above, for example, the tape speed is set at one-third of normal play, all of recorded MPEG data can be reproduced at one-third tape speed of normal play.
In the case of MPEG data, if tape speed is set at one-third of normal play and MPEG data is reproduced, usual MPEG decoder in digital broadcasting receiver may not decode the data and reproduce pictures from provided MPEG data. The reason of this is as follows.
In MPEG video data, the frame frequency of picture is fixed. Namely, if an original picture has 30 frames per second, MPEG data for one second also includes data of 30 frames. Further, each frame includes a relative time data (PTS: presentation time stamp) which designate the time when the frame is to be displayed. Then, if original data is simply provided to MPEG decoder at one-third of original speed, MPEG decoder can not reproduce pictures since the provided data having only 10 frames per second even though the original frame frequency being 30 Hz and there is also some contradiction in PTS.
Considering above, it is necessary for reproducing slow motion pictures that MPEG decoder has a special function for displaying MPEG data even if the MPEG data contains such contradictions described above.
SUMMARY OF THE INVENTION
The object of this invention is to provide an apparatus for reproducing MPEG data which apparatus makes it possible that any MPEG decoder without such special function can decode and display slow-motion picture without any contradiction.
In accordance with this and other objects, the present invention, an apparatus for reproducing MPEG data, is characterized for comprising means for providing picture data including original MPEG data without any modification at a normal speed play and means for providing picture data including original MPEG data and dummy picture data for repeatedly displaying the original picture data for several times in accordance with slow motion speed.
The dummy picture data for repeating original I picture and the dummy picture data for repeating original P picture is forward predictive B picture with zero differential data which means a motion vector value from a past reference picture is zero. The dummy picture data for repeating B picture is the original B picture itself.
The numbers of dummy picture data is so selected that sum of displayed picture numbers per second of original MPEG data and displayed numbers per second of the dummy picture data at the slow motion picture mode is equal to the displayed picture numbers per second of original MPEG data at the normal play mode.
REFERENCES:
patent: 5742728 (1998-04-01), Yanagihara et al.
patent: 6047101 (2000-04-01), Kawamura et al.
Minechika Shigekazu
Murashima Hirotsugu
Takashi Ohnaka
Tomikawa Masahiko
Michaelson Peter L.
Michaelson & Wallace
Nguyen Huy
Sanyo Electric Co. Ltd
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