Television – Format conversion
Reexamination Certificate
1995-08-17
2001-12-04
Faile, Andrew (Department: 2611)
Television
Format conversion
C348S443000, C348S458000
Reexamination Certificate
active
06326999
ABSTRACT:
This invention relates to data rate conversion and particularly, though not exclusively, to video data frame/field rate conversion.
FIELD OF INVENTION
BACKGROUND OF THE INVENTION
There are various ways of compressing video information. In particular, there are three standards under which compression may be carried out: JPEG, MPEG AND H.261. These are discussed, for example, in U.S. Pat. No. 5,212,742.
Video information is commonly formatted as a series of fields. The original information which is to be converted into, and displayed in, a video format may not be immediately compatible with the field rate at which the information is to be displayed. For example, a celluloid film is shot at a rate of 24 frame/sec. (24 Hz) while, for example, the NTSC television system has a field rate of almost 60 Hz. The technique of increasing the frame rate of the film images to match that of the television system film rate is known as pulldown conversion.
Continuing with the above example of displaying a film in a NTSC standard format, a ‘⅔pulldown’ conversion could be used in which each film frame is repeated for either two or three consecutive field periods at the video field repetition rate. The number of repetitions alternates so that the first frame is displayed twice in two consecutive field periods, the second frame is displayed three times in three consecutive field periods and so on. Thus, in one second twelve film frames at 24 Hz will each have been generated twice (i.e. for 24 field periods) while the other twelve film frames will each have been generated three times (i.e. for 36 field periods). The total (24+36) equals the 60 fields in one second at a 60 Hz field rate.
Pulldown instructions may be generated remotely and signalled to the video decoder associated with the displaying device or be generated locally at the video decoder. In the signalled pulldown, the encoder performs the pulldown calculations and signals specifically which frames are to be repeated, for example using the ‘repeat-first-field’ flag in the MPEG-2 video syntax. The decoder simply obeys the remotely generated instructions received.
In local pulldown, the encoder encodes the film information and transmits it to the receiving device. There is no information in the transmitted signal to tell the decoder at the receiving device how to perform the appropriate pulldown conversion (e.g. the ‘⅔ pulldown’ referred to above). The decoder must, therefore, calculate how to perform the appropriate conversion from the transmitted film frame rate to the displayed field rate.
If only pulldown conversion from the 24 Hz frame rate to a 60 Hz field rate were required, the single ⅔ pulldown conversion would be relatively easy to implement. However, other pulldown schemes are required. For example, the 24 Hz film frame rate may need to be converted to a 50 Hz field rate for the PAL television format.
Furthermore, an additional complexity in the NTSC television system is that the actual field rate is not 60 Hz but 60000/1001 Hz. Thus, the regular alternating ⅔ pulldown yields a field rate that is actually too high.
SUMMARY OF THE INVENTION
According to the invention there is provided a method of converting frames of data received at a slower rate into fields of data generated at a faster rate, the method comprising:
determining a basic integer number of repetitions of fields in a frame period;
calculating a differential of the field repetition rate from the difference between the ratio of the faster to the slower rates and the ratio of the basic repetition number of fields in the frame period to the slower frame rate;
additionally repeating or deleting selected ones of the repeated fields, when the differential of the rate of repeating fields is substantially at variance with the calculated differential of the field repetition rate, to maintain the repetition of the fields at the faster rate.
The terms ‘frame’ and ‘field’ are used for convenience. Both are intended to refer to any frame, field, packet or other discreet quantity of data sent, received and/or constructed as a set. The invention allows the selected repetition rate to be modified by the inclusion or extraction of frames of repeated and, therefore, redundant data to fulfill the faster field data rates. Preferably, the selected basic integer repetition rate is less than the faster field rate. In this case, the method will add additionally repeated frames at the repetition rate. The repetition rate may be less than half the field rate.
The method does not have to select a slower basic integer repetition rate. In the alternative, it could equally well select a faster rate and then the method would be arranged to delete repeated frames where necessary.
The invention also extends to apparatus for converting frames of data received at a slower rate into fields of data generated at a faster rate, the apparatus comprising:
means for determining a basic integer number of repetitions of fields in a frame period;
means for calculating a differential of the field repetition rate from the difference between the ration of the faster to the slower rates and the ratio of the basic repetition number of fields in the frame period to the slower frame rate;
means for additionally repeating or deleting selected ones of the repeated fields, when the differential of the rate of repeating fields is substantially at variance with the calculated differentials of the field repetition rate, to maintain the repetition of the fields at the faster rate.
REFERENCES:
patent: 3893042 (1975-07-01), Whitman et al.
patent: 3962685 (1976-06-01), Belle Isle
patent: 4107780 (1978-08-01), Grimsdale et al.
patent: 4142205 (1979-02-01), Iinuma
patent: 4149242 (1979-04-01), Pirz
patent: 4196448 (1980-04-01), Whitehouse et al.
patent: 4215369 (1980-07-01), Iijima
patent: 4302775 (1981-11-01), Widergren et al.
patent: 4334246 (1982-06-01), Saran
patent: 4433308 (1984-02-01), Hirata
patent: 4437072 (1984-03-01), Asami
patent: 4442503 (1984-04-01), Schutt et al.
patent: 4495629 (1985-01-01), Zaslo et al.
patent: 4540903 (1985-09-01), Cooke et al.
patent: 4580066 (1986-04-01), Berndt
patent: 4630198 (1986-12-01), I Yuan
patent: 4646151 (1987-02-01), Welles, II et al.
patent: 4679163 (1987-07-01), Arnould et al.
patent: 4689823 (1987-08-01), Wojcik et al.
patent: 4692880 (1987-09-01), Merz et al.
patent: 4747070 (1988-05-01), Trottier et al.
patent: 4785349 (1988-11-01), Keith et al.
patent: 4789927 (1988-12-01), Hannah
patent: 4799056 (1989-01-01), Hattori et al.
patent: 4799677 (1989-01-01), Frederiksen
patent: 4807028 (1989-02-01), Hatori et al.
patent: 4823201 (1989-04-01), Simon et al.
patent: 4829465 (1989-05-01), Knauer et al.
patent: 4831440 (1989-05-01), Borgers et al.
patent: 4831441 (1989-05-01), Ando
patent: 4866510 (1989-09-01), Goodfellow et al.
patent: 4866637 (1989-09-01), Gonzalez-Lopez et al.
patent: 4887224 (1989-12-01), Okano et al.
patent: 4891784 (1990-01-01), Kato et al.
patent: 4903018 (1990-02-01), Wiebach et al.
patent: 4912668 (1990-03-01), Aubie et al.
patent: 4922341 (1990-05-01), Strobach
patent: 4924298 (1990-05-01), Kitamura
patent: 4924308 (1990-05-01), Feuchtwanger
patent: 4975596 (1990-12-01), Roberts et al.
patent: 4991112 (1991-02-01), Callemyn
patent: 5003204 (1991-03-01), Cushing et al.
patent: 5027212 (1991-06-01), Marlton et al.
patent: 5038209 (1991-08-01), Hang
patent: 5053985 (1991-10-01), Friedlander et al.
patent: 5057793 (1991-10-01), Cowley et al.
patent: 5060242 (1991-10-01), Arbeiter
patent: 5081450 (1992-01-01), Lucas et al.
patent: 5086489 (1992-02-01), Shimura
patent: 5091721 (1992-02-01), Harnori
patent: 5107345 (1992-04-01), Lee
patent: 5111292 (1992-05-01), Kuriacose et al.
patent: 5113255 (1992-05-01), Nagata et al.
patent: 5122873 (1992-06-01), Golin
patent: 5122875 (1992-06-01), Raychaudhuri et al.
patent: 5124790 (1992-06-01), Nakayama
patent: 5126842 (1992-06-01), Andrews et al.
patent: 5129059 (1992-07-01), Hannah
patent: 5130568 (1992-07-01), Miller et al.
patent: 5134487 (1992-07-01), Taguchi et al.
patent: 5134697 (
Discovision Associates
Faile Andrew
Masaki Keiji
Srivastava Vivek
Stokey Richard
LandOfFree
Data rate conversion does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Data rate conversion, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Data rate conversion will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2598261