DESCRIPTION
This is a continuation of U.S. patent application Ser. No. 33,905, filed Apr. 27, 1979 and entitled A METHOD OF POST PRODUCTION SOUND RECORDING FOR VIDEO TAPE PROGRAM in the name of Clarence Robert Fine now abandoned.
This invention relates to a method of synchronizing audio and video information. More specifically, the present invention relates to a process for producing a video tape of the type used in television broadcasting wherein motion picture techniques for synchronizing sound and video may be employed without sacrificing the advantages of modern video editing procedures.
BACKGROUND OF THE INVENTION
In the early days of television, most programs were live or optically recorded (kinescoped) on conventional motion picture film. In such cases, no editing was required. In some cases, a program was recorded on motion picture film and conventional motion picture techniques for editing and synchronizing the sound and visual tracks could be used.
Technological advances in the art of recording video information have increased the desirability of recording television programs on video tape directly. This requires that the video be edited to provide the desired visual effect and also that a sound track be prepared in which the sound effects and dialogue are exactly synchronized with the recorded video.
In recording on video tape, it is common practice to record a time code identifying each recorded frame on the tape medium. The standard time code used in the United States (and other countries which have 30 frame NTSC television is referred to as the SMPTE time code which comprises an 80-bit code of which 43 bits are used to identify the recording time (in hours, minutes and seconds) for each frame and the number of the frame on the tape. In countries where 25 frames per second is standard, the code is referred to as the EBU time code. The use of this SMPTE time code has enabled sophisticated computer controlled techniques for editing video signals and, currently, the editing of video tape is more efficient than the editing of motion picture film wherein various film effects must be spliced together to provide a finished product.
Despite the sophistication of currently available video editing techniques, there is a problem in synchronizing an audio track with the recorded video. As an example, in producing a video tape, it may be necessary to synchronize music tracks, dialogue tracks and tracks containing various types of sound effects. Each one of these tracks (sometimes referred to as a sound mixing element) must be prepared using a time lock system dependent on the recorded SMPTE time code so that the audio and video signals are synchronized exactly. In practice, this is a very expensive undertaking since costly computer equipment must be used to synchronize and prepare the mixing elements on a multi-track tape. Because of the expense involved in revising a recorded element or track, as a practical matter, artistic compromises frequently arise in cases where a director is partially dissatisfied with one or more of the mixing elements. Moreover, the inability of the director or editor to "feel" the visual medium with which he is working as the sound track is created diminishes the feeling of an artistic or creative contribution. All of these factors have limited the acceptance by industry of direct video recording of television programs.
OBJECTS OF THE INVENTION
The principal object of the invention is to provide a simplified and inexpensive method of synchronizing audio and recorded video signals.
A more specific object of the invention is to enable the use of conventional film synchronizing techniques for post production sound mixing of video tapes.
BRIEF SUMMARY OF THE INVENTION
Briefly, in accordance with the invention, a master edited video tape is prepared containing a video signal and a recorded time code identifying each frame. The video signal is then transferred to a first sprocketed magnetic film which may operate at a standard motion picture speed. Using this film as a work print, a plurality of audio tracks are produced in synchronism with the video information recorded on the work print. Thereafter, the recorded audio tracks are mixed to form a master finished audio track which is recorded on a second sprocketed magnetic film together with the time code of the original master edited video tape.
The audio and video signals may then be combined by using the recorded time codes on the finished audio film and the master edited video tape to drive them in synchronism as the audio is transferred to the video tape.
THE DRAWINGS
FIG. 1 is a flow chart showing the steps involved in practicing the invention;
FIG. 2 is a block diagram showing the means for synchronizing the master edited video tape and the master finished audio film; and
FIG. 3 is a diagrammatic illustration showing the layout of a video tape machine modified to record on and reproduce from a sprocketed magnetic film.
DETAILED DESCRIPTION
The process according to the invention contemplates the use of conventional video editing techniques in conjunction with motion picture sound synchronizing techniques. Although there is no known commercially available apparatus for performing the process of the invention, the modifications of existing devices required to practice the invention will be apparent to those of ordinary skill in the art in the light of the following description. Accordingly, this specification does not include a detailed description of the physical construction of the various devices and machines used to practice the invention.
The following description may be read in conjunction with the flow diagram of FIG. 1 in which the various steps of the invention are recounted sequentially from top to bottom.
In practicing the invention, it is necessary to first produce (or have produced) a master edited video tape. Conventionally, this may be accomplished by the use of a number of cameras recording a given scene from different angles. At the same time, an audio track containing the dialogue of the scene involved is recorded in conventional fashion on the tape. The director then edits the recorded video, most advantageously by computerized editing equipment, to produce a master edited video tape. Typically, the video is recorded by quadraplex scanning techniques on two-inch magnetic tape or by helical scanning techniques on one inch magnetic tape about 0.5 mils thick.