This invention relates to techniques for electronically editing film.
Film video and audio source material is frequently edited digitally using a computer system, such as the Avid/1 Media Composer from Avid Technology, Inc., of Tewksbury, Mass., which generates a digital representation of a source film, allowing a film editor to edit the digital version, rather than the film source itself. This editing technique provides great precision and flexibility in the editing process, and is thus gaining popularity over the old style of film editing using a flatbed editor.
The Avid/1 Media Composer accepts a videotape version of a source film, created by transferring the film to videotape using the so-called telecine process, and digitizes the videotape version for editing via manipulation by computer. The operation of the Media Composer is described more fully in copending application U.S. Ser. No. 07/866,829, filed Apr. 10, 1992, and entitled Improved Media Composer. The teachings of that application are incorporated herein by reference. Editing of the digitized film version is performed on the Media Composer computer using CRT monitors for displaying the digitized videotape, with the edit details being based on videotape timecode specifications. Once editing is complete, the Media Composer creates an edited videotape and a corresponding edit decision list (EDL) which documents the videotape timecode specification details of the edited videotape. The film editor uses this EDL to specify a cut and assemble list for editing the source film. While providing many advantages over the old style flatbed film editing technique, this electronic editing technique is found to be cumbersome for some film editors who are unaccustomed to videotape timecode specifications.
In general, in one aspect, the invention provides a system for generating a digital representation of a video signal comprised of a sequence of video frames which each include two video fields of a duration such that the video plays at a first prespecified rate of frames per second. The sequence of video frames includes a prespecified number of redundant video fields. In the invention, redundant video fields in the video frame sequence are identified by a video processor, and the video frame sequence is digitized by an analog to digital converter, excluding the identified redundant video fields. The digitized video frames axe then compressed by a video compressor to generate a digital representation of the video signal which plays at a second prespecified rate of frames per second.
In preferred embodiments, the invention further provides for storing the digitized representation of the video signal on a digital storage apparatus. The redundant video fields are identified by assigning a capture mask value to each video field in the video frame sequence, the capture mask value of a field being a “0” if the field is redundant, and the capture mask value of a field being a “1” for all other video fields. A video frame grabber processes the video frame sequence based on the capture mask values to exclude the identified redundant video frames from being digitized. The video compressor compresses the video frames based on JPEG video compression.
In other preferred embodiments, the first prespecified video play rate is 29.97 frames per second and the second prespecified digital video play rate is 24 frames per second. The rate of the analog video signal is increased from 29.97 frames per second to 30 frames per second before the step of digitizing the video frame sequence. In further preferred embodiments, the analog video signal is a video representation of film shot at 24 frames per second, and the digital video play rate of 24 frames per second corresponds to the 24 frames per second film shooting rate. The analog video signal is a representation of film that is transferred to the video representation using a telecine apparatus.
In general, in another aspect, the invention provides an electronic editing system for digitally editing film shot at a first prespecified rate and converted to an analog video representation at a second prespecified rate. The editing system includes analog to digital converting circuitry for accepting the analog video representation of the film, adjusting the rate of the analog video such that the rate corresponds to the first prespecified rate at which the film was shot, and digitizing the adjusted analog video to generate a corresponding digital representation of the film. Further included is a digital storage apparatus for storing the digital representation of the film, and computing apparatus for processing the stored digital representation of the film to electronically edit the film and correspondingly edit the stored digital representation of the film.
In preferred embodiments, the system further includes digital to analog converting circuitry for converting the edited digital representation of the film to an analog video representation of the film, adjusting the rate of the analog video from the first prespecified rate to the second prespecified video rate, and outputting the adjusted analog video. Preferably, the analog video representation of the film accepted by the analog to digital converting circuitry is an NTSC videotape. The apparatus for storing the digital representation of the film also stores a digitized version of a film transfer log corresponding to the digital representation of the film. The system includes display apparatus for displaying the digitized version of the film as the film is electronically edited and displaying a metric for tracking the location of a segment of the film as the segment is displayed, the metric being based on either film footage code or video time code, as specified by the system user.
The electronic editing system of the invention allows users to provide the system with film formatted on standard videotapes, NTSC tapes, for example, and yet allows the video to be digitally edited as if it were film, i.e., running at film speed, as is preferred by most film editors. By reformatting the analog video as it is digitized, the system provides the ability to electronically edit film based on the same metric used in conventional film editing.
Referring to
In operation, video and audio source material from a film which has been transferred to a videotape is received by the system via the video tape recorder 20, and is preprocessed and digitized by the audio A/D 22, audio processor 24, video A/D 26, and video compressor 30, before being stored in the disc storage 32. The computer is programmed to display the digitized source video on a first of the CRTs 12 and play the accompanying digitized source audio on the audio output 16. Typically source material is displayed in one window 36 of the first CRT 12 and edited material is displayed in a second window 38 of that CRT. Control functions, edit update information, and commands input from the keyboard 32 are typically displayed on the second system CRT 14.
Once a film is input to the system, a film editor may electronically edit the film using the keyboard to make edit decision commands. As will be explained in detail below, the electronic editing system provides the film editor with great flexibility, in that the video displayed, on the system CRT 12 may be measured and controlled in either the domain of film footage or the domain of videotape time code. This flexibility provides many advantages over prior electronic editing systems. At the end of an editing session, the electronic editing system provides the film editor with an edited videotape and both tape and film edit command lists for effecting the edits from the session on film or videotape.
As explained above, the electronic editing system 10 requires a videotape version of a film for electronic manipulation of that film. Such a tape is preferably generated by a standard film-tape transfer process, the telecine process, which preferably uses the Time Logic Controller™ telecine (TLC), a device that converts film into a video signal, then records the signal on videotape. A TLC controls the film-tape transfer more precisely than non-TLC systems. In addition, it outputs a report, described below, that includes video format specifications, i.e., timecode, edge number, audio timecode, scene, and take for each reference frame in each tape, thereby eliminating the need to search through the video or film footage manually to find the data required for creating a log of video playing particulars. Other telecine systems may be used, however, depending on particular applications.
Transfer from film to tape is complicated by the fact that film and video play at different rates-film plays at 24 frames per second (fps), whereas PAL video plays at 25 fps and NTSC (National Television Standards Committee) video plays at 29.97 fps. If the film is shot at the standard rate of 24 fps and then transferred to 29.97 fps NTSC video, the difference between the film and video play rates is large (and typically unacceptable). As a result, the film speed, must be adjusted to accommodate the fractional tape speed, and some film frames must be duplicated during the transfer so that both versions have the same duration. However, if the film is shot at 29.97 fps, then transferring the footage to NTSC video is simple. Each film frame is then transferred directly to a video frame, as there are the same number of film and video frames per second.
Considering the most common case, in which 24 fps film is to be transferred to 29.97 fps NTSC videotape, the telecine process must provide both a scheme for slowing the film and a frame duplication scheme. The film is slowed down by the telecine apparatus by 0.1% of the normal film speed, to 23.976 fps, so that when the transfer is made, the tape runs at 29.97 fps, rather than 30 fps. To illustrate the frame duplication scheme, in the simplest case, and disregarding the film slow-down requirement, one second of film would be transferred to one second of video. The one second of film would include 24 frames of film footage, but the corresponding one second of video would require 30 frames of footage. To accommodate this discrepancy, the telecine process duplicates one film frame out of every four as the film is transferred to tape, so that for each second of film footage, the corresponding second of tape includes six extra frames.
Each video frame generated by the telecine process is actually a composite of two video fields: an odd field, which is a scan of the odd lines on a video screen, and an even field, which is a scan of the even lines. A video field consists of 262½ scan lines, or passes of an electron beam across a video screen. To create a full video frame comprised of 525 scan lines, an odd field, or scan of the odd lines, is followed by an even field, or scan of the even lines. Thus, when a duplicate video frame is generated and added in the telecine process, duplicate video fields are actually created. During play of the resulting tape, each two video fields are interlaced to make a single frame by scanning of the odd lines (field one) followed by scanning of the even lines (field two) to create a complete frame of NTSC video.
There are two possible systems for creating duplicate video fields in the telecine process, those systems being known as 2-3 pulldown and 3-2 pulldown. The result of the 2-3 pulldown process is schematically illustrated in
Referring to
A further film-tape correspondence is generated by the telecine process. This is required because, in addition to the difference between film and video play rates, the two media employ different systems for measuring and locating footage. Film is measured in feet and frames. Specific footage is located using edge numbers, also called edge code or latent edge numbers, which are burned into the film. For example, Kodak film provides Keykode™ on the film to track footage. The numbers appear once every 16 frames, or once every foot, on 35 mm film. The numbers appear once every 20 frames, or every half foot, on 16 mm film. Note that 35 mm film has 16 frames per foot, while 16 mm film has 40 frames per foot. Each edge number includes a code for the film manufacturer and the film type, the reel, and a footage counter. Frames between marked edge numbers are identified using edge code numbers and frame offsets. The frame offset represents the frame's distance from the preceding edge number.
Videotape footage is tracked and measured using a time-base system. Time code is applied to the videotape and is read by a time code reader. The time code itself is represented using an 8-digit format: XX-XX-XX-XX—hours:minutes:seconds:frames. For example, a frame occurring at 11 minutes, 27 seconds, and 19 frames into the tape would be represented as 00:11:27:19.
It is preferable that during the telecine conversion, a log, called a Film Transfer Log (FTL), is created that makes a correspondence between the film, length-base and the video time-base. The FTL documents the relationship between one videotape and the raw film footage used to create that tape, using so-called sync points. A sync point is a distinctive frame located at the beginning of a section of film, say, a clip, or scene, which has been transferred to a tape. The following information documents a sync point: edge number of the sync point in the film footage, time code of the same frame in the video footage, the type of pulldown sequence used in the transfer, i.e., 2-3 pulldown or 3-2 pulldown, and the pulldown mode of the video frame, i.e., which of the A, B, C, and D frames in each film five-frame series corresponds to the sync point frame.
As shown in
The electronic editing system of the invention accepts a videotape produced by the telecine process and an Evertz FTL, stored on, for example, a floppy disk. When the FTL data on the disk is entered into the system, the system creates a corresponding bin in memory, stored on the system disc, in analogy to a film bin, in which film clips are stored for editing. The electronic bin contains all fields necessary for film editing, all comments, and all descriptions. The particulars of the bin are displayed for the user on one of the system's CRTs.
Referring again to
In operation, the video A/D 26 processes the video signal to reformat the signal so that the video represented by the signal corresponds to film speed, rather than videotape speed. The reformatted signal is then digitized, compressed, and stored in the computer for electronic film editing. This reformatting process allows users to provide the editing system with standard videotapes, in NTSC format, yet allows the video to be edited as if it were film, i.e., running at film speed, as is preferred by most film editors.
Referring also to
Assuming the use of the 2-3 pulldown scheme, as discussed above, in the capture process, the first two analog video fields (AA in
Appendix A of this application consists of an example of assembly language code for the Macintosh™ computer and the TI 34010 coprocessor for performing the reformatting process. This code is copyrighted, and all copyrights are reserved.
Referring again to
There are traditionally three different types of film productions that shoot on film, each type having different requirements of the electronic editing system. The first film production type, commercials, typically involves shooting on 35 mm film, transferring the film to a videotape version using the telecine process, editing the video based on the NTSC standard, and never editing the actual film footage, which is not again needed after the film is transferred to video. Thus, the electronic editing is here preferably based on video timecode specifications, not film footage specifications, and an NTSC video is preferably produced at the end of the edit process. The electronic commercial edit should also preferably provide an edit decision list (EDL) that refers back to the video; the edited version of this video is typically what is actually played as the final commercial.
The second production type, episodic film, involves shooting on either 35 or 16 mm film, and producing an NTSC videotape version and additionally, an (optional) edited film version for distribution in markets such as HDTV (High Definition Television) or foreign countries. To produce the edited film footage for the film version, the film is transferred to videotape using the telecine process, and electronic editing of the film is here preferably accomplished based on film footage, and should produce a cutlist, based on film footage specifications, from which the original film is cut and transferred to the NTSC format. To produce a video version, the videotape is then preferably edited based on video timecode specifications to produce an EDL for creating an edited video version.
The third film production type, feature film, typically involves shooting on 35 mm film, and produces a final film product; thus electronic editing is here preferably based on film footage specifications to produce a cutlist for creating a final film version.
The user interface of the electronic editing system is designed to accommodate film editors concerned with any of the three film production types given above. As shown in
As an example of an editing session, one scene could be selected from the bin and played on the source window 36 of the system CRT display 12. A film editor could designate frame points to be moved or cut in either timecode or film footage format. Correspondingly, audio points could be designated to be moved or the audio level increased (or decreased). When it is desired to preview a video version of such edits, an NTSC video is created by the system based on the sync information in the electronic bin, from the system disc storage, to produce either a so-called rough cut video, or a final video version. In this process, the system generates an analog version of the digital video signal and restores the redundant video frames necessary for producing the NTSC video rate. The system also produces a corresponding analog audio track and decreases the audio speed so that the audio is synchronized with the video. In this way, the system essentially mimics the telecine process by slowing down the video and audio and producing a 29.97 fps videotape based on a 24 fps source.
Referring again to
The electronic editing system may be programmed to produce an edit listing appropriate to the particular media on which the finalized version of the film source material is to appear. If the source film material is to be finalized as film, the system may be specified to produce a cut list. The cut list is a guide for conforming the film negative to the edited video copy of the film footage. It includes a pull list and an assemble list. The assemble List provides a list of cuts in the order in which they must be spliced together on the film. The pull list provides a reel-by-reel listing of each film cut. Each of these lists specifies the sync points for the cuts based on film footage and frame keycode, as if the film had been edited on a flatbed editor. If the source film material is to be finalized as video, the system may be specified to produce an edit decision list (EDL). The EDL specifies sync points in video time code, as opposed to film footage. The editing system generates the requested edit fists based on the electronic bin; as the film is electronically edited, the bin reflects those edits and thus is a revised listing of sync points corresponding to the edited film version. Because the bin is programmed to specify sync points in both film, footage and video timecode, the editing system has direct access to either format, and can thereby generate the requested EDL or assemble and pull lists. Appendix B consists of examples of an EDL, assemble lists, and pull lists, all produced by the electronic editing system. Thus, at the end of an electronic film edit, the editing system provides a film editor with an NTSC videotape of the film edits and a edit list for either film or videotape.
Other embodiments of the invention are within the scope of the claims.
This application is a CONTINUATION application of and claims the benefit under 35 U.S.C §120 of the filing date of: U.S. patent application Ser. No. 10/657,800, filed Sep. 8, 2003, entitled ELECTRONIC FILM EDITING SYSTEM USING BOTH FILM AND VIDEOTAPE FORMAT, pending, which is a continuation of U.S. patent application Ser. No. 09/304,932, filed May 4, 1999, entitled ELECTRONIC FILM EDITING SYSTEM USING BOTH FILM AND VIDEOTAPE FORMAT, issued as U.S. Pat. No. 6,618,547 on Sep. 9, 2003, which is a continuation of both U.S. patent application Ser. No. 08/393,877, filed Feb. 24, 1995, entitled ELECTRONIC FILM EDITING SYSTEM USING BOTH FILM AND VIDEOTAPE FORMAT, and now U.S. Pat. No. 5,930,445, issued Jul. 27, 1999, and U.S. patent application Ser. No. 08/393,886, filed Feb. 24, 1995, entitled ELECTRONIC FILM EDITING SYSTEM USING BOTH FILM AND VIDEOTAPE FORMAT, and now U.S. Pat. No. 5,905,841, issued May 18, 1999, which are a divisional application, and continuation application, respectively, of application Ser. No. 07/908,192, filed Jul. 1, 1992, now abandoned; andU.S. patent application Ser. No. 09/304,932, filed May 4, 1999, entitled ELECTRONIC FILM EDITING SYSTEM USING BOTH FILM AND VIDEOTAPE FORMAT, issued as U.S. Pat. No. 6,618,547 on Sep. 9, 2003, which is a continuation of both U.S. patent application Ser. No. 08/393,877, filed Feb. 24, 1995, entitled ELECTRONIC FILM EDITING SYSTEM USING BOTH FILM AND VIDEOTAPE FORMAT, and now U.S. Pat. No. 5,930,445, issued Jul. 27, 1999, and U.S. patent application Ser. No. 08/393,886, filed Feb. 24, 1995, entitled ELECTRONIC FILM EDITING SYSTEM USING BOTH FILM AND VIDEOTAPE FORMAT, and now U.S. Pat. No. 5,905,841, issued May 18, 1999, which are a divisional application, and continuation application, respectively, of application Ser. No. 07/908,192, filed Jul. 1, 1992, now abandoned; andU.S. patent application Ser. No. 08/393,877, filed Feb. 24, 1995, entitled ELECTRONIC FILM EDITING SYSTEM USING BOTH FILM AND VIDEOTAPE FORMAT, and now U.S. Pat. No. 5,930,445, issued Jul. 27, 1999, which is a divisional application of application Ser. No. 07/908,192, filed Jul. 1, 1992, now abandoned; andU.S. patent application Ser. No. 08/393,886, filed Feb. 24, 1995, entitled ELECTRONIC FILM EDITING SYSTEM USING BOTH FILM AND VIDEOTAPE FORMAT, and now U.S. Pat. No. 5,905,841, issued May 18, 1999, which is a continuation of application Ser. No. 07/908,192, filed Jul. 1, 1992, now abandoned; andU.S. patent application Ser. No. 07/908,192, filed Jul. 1, 1992, now abandoned.
Number | Date | Country | |
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Parent | 07908192 | Jul 1992 | US |
Child | 08393886 | US | |
Parent | 07908192 | Jul 1992 | US |
Child | 08393886 | US | |
Parent | 07908192 | Jul 1992 | US |
Child | 08393877 | US |
Number | Date | Country | |
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Parent | 10657800 | Sep 2003 | US |
Child | 12156634 | US | |
Parent | 09304932 | May 1999 | US |
Child | 10657800 | US | |
Parent | 08393877 | Feb 1995 | US |
Child | 09304932 | US | |
Parent | 08393886 | Feb 1995 | US |
Child | 08393877 | US | |
Parent | 07908192 | Jul 1992 | US |
Child | 07908192 | US | |
Parent | 09304932 | May 1999 | US |
Child | 07908192 | US | |
Parent | 08393877 | Feb 1995 | US |
Child | 09304932 | US | |
Parent | 08393886 | Feb 1995 | US |
Child | 08393877 | US | |
Parent | 07908192 | Jul 1992 | US |
Child | 07908192 | US | |
Parent | 08393877 | Feb 1995 | US |
Child | 07908192 | US | |
Parent | 08393886 | Feb 1995 | US |
Child | 07908192 | US | |
Parent | 07908192 | Jul 1992 | US |
Child | 08393886 | US | |
Parent | 07908192 | Jul 1992 | US |
Child | 07908192 | US |