Television – Special applications – Film – disc or card scanning
Reexamination Certificate
1997-07-07
2001-05-01
Lee, Young (Department: 2613)
Television
Special applications
Film, disc or card scanning
C348S441000
Reexamination Certificate
active
06226033
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to conversion of film to video, post-production of video, conversion of video to film, and conversion between different video formats.
2. Description of the Prior Art
A vast amount of film masters are in a 24 frame/s or 25 frame/s format, and often it is required to convert the film to video for distribution, post-production and broadcast transmission, and to convert the video back to film as a sub-master. One standard format for video employs interlaced fields at 60 field/s. For example, the SMPTE 240M high definition format employs 1125 line/frame, 2:1 interlace, 60 field/s. Because of the difference in frame rate between the film and video, there is no one-to-one correspondence between the film frames and the video frames, and this presents a problem.
A partial solution to this problem in the case of 24 frame/s film (and also 25 frame/s film if a slightly incorrect speed is not unacceptable) is to use a 3232 format for the video. With 3232, there is a correspondence between a series of four film frames and ten video fields as follows:
Film
Video
Frame 1
Frame 1 odd field
Frame 1
Frame 1 even field
Frame 1
Frame 2 odd field (additional)
Frame 2
Frame 2 even field
Frame 2
Frame 3 odd field
Frame 3
Frame 3 even field
Frame 3
Frame 4 odd field
Frame 3
Frame 4 even field (additional)
Frame 4
Frame 5 odd field
Frame 4
Frame 5 even field
It will therefore be appreciated that the real-time relationship between 24 frame/s film and 60 field/s video is maintained (at least when averaged over a four film frame period), but that two of the video fields, frame
2
odd and frame
4
even, are duplicated, and so the fields of video frame
2
do not correspond to a single film frame and likewise with the fields of video frame
3
. During post-production of 3232 video, for example combining two 3232 video signals, there is the problem of synchronising the additional fields of the signals, so that if the video is later converted back to film the additional fields can be dropped and the other fields can all be maintained. Subsequent conversion to 50 field/s video compounds the problem, because every sixth field needs to be dropped. Sometimes the dropped field will be an additional field, and sometimes it will not.
SUMMARY OF THE INVENTION
The video signal according to the invention
In accordance with one aspect of the present invention, there is provided a video signal, such as a 1125 lines/frame high definition video signal, representing material which is acquired or generated at a real-time rate, wherein the video signal is in a 60 field/s format at 1.25 or 1.2 times the real-time rate. Such a video signal will hereinafter be referred to as a “gateway” video signal.
The gateway video signal provides a number of advantageous possibilities, including:
frame-locked transfer of material from real-time 24 frame/s and 25 frame/s film to the gateway format;
frame-accurate post-production editing not requiring a 3232 relationship and retaining the gateway format;
real-time post-production editing with a synchronised 3232 relationship between different sources and the product; and
frame-locked transfer of material from the gateway format to real-time 24 frame/s or 25 frame/s film and 50 field/s video.
In the case where source material is 24 frame/s film, the gateway video signal is at 1.25 times the real-time rate, hereinafter referred to as a “125% gateway” signal. In the case where the source material is 25 frame/s film, the gateway video signal is at 1.2 times the real-time rate, hereinafter referred to as a “120% gateway” signal.
Conversion of film to Gateway video
Very conveniently, a 30 frame/s telecine may be used to produce a 125% gateway signal from 24 frame/s film, and to produce a 120% gateway signal from 25 frame/s film.
Conversion of conventional 60 Hz video to Gateway video
The invention also provides a (first) method of converting a source 60 field/s video signal to a gateway video signal, comprising the step of dropping every fifth field from the source signal for 125% gateway video or dropping every sixth field from the source signal for 120% gateway video.
The invention furthermore provides a (first) apparatus for reproducing a gateway video signal from a source 60 field/s video signal recording, the apparatus including means for reproducing and outputting four out of every five fields of the recorded video signal for a 125% gateway signal, or five out of every six fields of the recorded video signal for a 120% gateway signal. Preferably, said reproducing and outputting means comprises means for reproducing the recording at 75 field/s for 125% gateway or 72 field/s for 120% gateway, and means for outputting four out of every five, or five out of every six, as the case may be, of the reproduced fields at 60 field/s.
Conversion of Gateway video to film.
Very conveniently, a 30 frame/s electron beam recorder (“EBR”) may be used to produce a film from a gateway signal. In the case of 125% gateway video, this will produce film whose proper speed is 24 frame/s, but for which viewing at 25 frame/s may be acceptable in many cases. In the case of 120% gateway video, this will produce film whose proper speed is 25 frame/s, but for which viewing at 24 frame/s may be acceptable in many cases.
Conversion of Gateway video to normal speed 60 field/s video
The invention provides a (second) method of converting a gateway video signal to a second real-time, or nearly real-time, 60 field/s video signal, comprising the step of duplicating every fourth field of the gateway signal to produce the second signal. This produces a real-time signal from a 125% gateway video signal, and a signal which is 0.96 of real-time from a 120% gateway signal. This method preferably further comprises the step of keeping track of the duplicated fields.
The invention also provides a (second) apparatus for reproducing a 60 field/s video signal from a recording of a gateway signal, the apparatus including means for reproducing the fields of the recorded video signal and duplicating every fourth reproduced field. In this case, the reproducing and duplicating means preferably comprises means for reproducing the recorded signal at 48 field/s and means for duplicating every fourth field to provide a field rate of 60 field/s. Preferably, means is provided for keeping track of the duplicated fields.
The invention also provides a (third) method of converting a gateway video signal to a second real-time, or nearly real-time, 60 field/s video signal, comprising the step of duplicating every fifth field of the gateway signal to produce the second signal. This produces a real-time signal from a 120% gateway video signal, and signal which is 1.042 of real-time from a 125% gateway signal. The method preferably further comprises the step of keeping track of the duplicated fields.
The invention also provides a (third) apparatus for reproducing a 60 field/s video signal from a recording of a gateway signal, the apparatus including means for reproducing the fields of the recorded video signal and duplicating every fifth reproduced field. In this case, the reproducing and duplicating means preferably comprises means for reproducing the recorded signal at 50 field/s and means for duplicating every fifth field to provide a field rate of 60 field/s. Preferably, means is included for keeping track of the duplicated fields.
Conversion of Gateway video to normal speed 50 field/s video
Optionally, the third method further comprises the step of conversion from the second signal to a 50 field/s video signal by dropping one in every six fields of the second signal. Preferably, the dropped fields are the fields which were duplicated when producing the second signal from the gateway signal.
Optionally, the third apparatus further comprises means, such as a 1125 lines, 60 field/s to 1250 lines, 50 field/s standards converter, or a 1125 lines, 60 field/s to 625 lines, 50 field/s standards converter, for dropping one in every six fields of the 60 field/s signal, preferably the dupl
Frommer William S.
Frommer Lawrence & Haug LLP.
Lee Young
Savit Glenn F.
Sony Corporation
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