Conforming & Editing (EDLs / AAF)

Film editing is the fine art of storytelling practiced by connecting two or more shots together to form a sequence, and the subsequent connecting of sequences to form an entire movie. Almost every motion picture, television show and TV commercial is shot with one camera per take; every single shot is separated from every other single shot by time and space. On its most fundamental level, film editing is the art, technique, and practice of assembling these shots into a coherent whole. However, the job of an editor isn’t merely to mechanically put pieces of a film together, nor is it to just cut off the film slates, nor is it simply to edit dialogue scenes. A film editor works with the layers of images, the story, the music, the rhythm and the pace which shapes the actors' performances, "re-directing" and often re-writing the film during the editing process, honing the infinite possibilities of the juxtaposition of small snippets of film into a creative, coherent, cohesive whole.

I previously mentioned only one camera, more than likely several cameras will have captured the scene or event at the same time, therefore making the editor spend time working out which shot works best and at what angle, wide or close up. This is where editing and being able to review many different sequences on a layered timeline helps the director work out best how to represent their vision, although we are also now seeing multiple camera views within one scene or different views covering one sequence.

The editorial process by the time it reaches DI has supposedly been locked. In truth I’ve never seen many films where the edit has not been tinkered with. Once they have removed themselves from the edit suite to a plush cinema or colour-grading suite, ultimately seeing the final mastered timeline in all of its glory, (high definition or 2K) for some can be a harrowing experience.

This has been, in my experience when the director and director of photography (DOP) have suddenly been frightened and panicked by their own work. Unfortunately the checking procedure throughout production paints a different picture to the final raw scans used for the DI process. Watching small resolution infinitely compressed images, throughout the editorial stage taken from the rushes dailies tapes can paint a hugely different story. Which incidentally will almost certainly have been colour corrected by the telecine operator, sometimes painting a somewhat rosier picture than what is captured on the actual negative.

Data Dailies

Ultimately the only true way of representing what is on the negative and in my opinion a far better way of working, would be to scan the negative from the start and offer a true representation without the often misguided but hopefully keen colourist’s interpretation of a scene. Subtle colour lighting can be graded out to normalise what the DOP was after, or alternatively a shot that looks great from the telecine may have been under or over exposed, which is not noticeable gauging from the rushes. HD rushes are making the process easier but you still cannot remove the telecine operator from trying to make the scene look beautiful, when sometimes they simply are not.

Data Dailies are beginning to be offered and take this uncertainty away from the rigmarole of rushes. These are not unlike scans but are smaller resolution versions that can be viewed from Digi Beta, they are a technical scan of what is exactly on the negative, removing the subjective ‘Colourist’ from the equation. This would give a far more reliable approach to this problem, which will always remain while a colourist is able to subject their individual vision of the scene.

Another problem with telecine transfers is that all sorts of tricks and operations can be applied to the image to make it look good. High grain can be smoothed or softened; out of focus shots can be digitally sharpened and ultimately change the way something is looking. If the director had the knowledge before the scene is wrapped, he or she may have been able to go back and re shoot, saving a 'fix it in post' mentality that is industry rife. A set may have been dismantled making it to expensive to shoot a pick up or revisit it! (Only in post production can you start to approach these shots, this is the kind of thing I shall discuss in the effects section. These are not the kind of effects you may associate with film but they have a strong part to play within the Digital Intermediate process.)


A quick note about Offline/Online

Offline editing is the film and television production process in which raw footage is copied and edited digitally, without affecting the camera original film or tape, you had to be very experienced not to cause damage to negative while editing a film. Once a film or programme has been completed in offline, the original media will be conformed, or on-lined, in the online editing stage. It is useful to note that Onlining does not cause any degradation of the material, unless it is compressed on the disk. Tape to tape transfers of old cause 'generation loss' - this only refers to tape mastering, which is something else to bear in mind when dubbing your deliverables.

Modern offline editing is conducted in a non-linear editing suite. The digital revolution has made the offline editing process immeasurably quicker, as practitioners moved from time-consuming negative copying and editing, butt splicing and movieola’s, linear (tape to tape) suites were then replaced by computer hardware and software such as Adobe Premiere, Final Cut Pro, Avid, Vegas Video and Lightworks. Typically, all the original footage (often tens or hundreds of hours) is digitized into the suite at an extremely low resolution. The editor and director are then free to work with all the options to create the final cut or master timeline.


When the offline edit is complete, the pictures are re-assembled at full or 'online' resolution, usually 2K. An edit decision list or equivalent (AAF) is used to carry over the cuts and dissolves from the offline. This ‘final’ conform is checked against a video copy of the offline edit to verify that the edits are correct and frame-accurate. As well, this cutting copy provides a reference for any video effects and working copy that need to be added.

DPX (Cineon)

Digital Picture Exchange (DPX) is now a common file format used for digital intermediate and visual effects work and has been ratified as an ANSI/SMPTE standard (268M-2003). The file format is most commonly used to represent the density of each colour channel of a scanned negative in a 10-bit log format where the gamma of the original camera negative is preserved as taken by a film scanner. Other common video formats are also supported. DPX provides a great deal of flexibility in storing colour and other information for exchange between production facilities.

The DPX file format was originally derived from the output file format (.cin) of the Kodak Cineon 'FIDO' film scanner, but the difference is that DPX can hold Linear or LOG data. Cineon is only a LOG format. The header information within DPX files contains three sections in addition to picture data:

  1. generic file information including data format
  2. motion picture and television industry specific information such as film perforation edge number or video timecode information
  3. user-defined information which may include ASCII data. Since each DPX frame is "one of tens of thousands" in a motion picture, users will track intellectual/bibliographic metadata separately from the set of DPX files

Each DPX file represents a single image with a single component, e.g. luma, or multiple components, e.g., red, green, blue; or Cb, Y, Cr (chrominance-luminance data). Many variations in multiple component data are supported. DPX images may be produced by scanning film or by using a camera that produces a DPX output. DPX files can be any resolution but are usually HD, 2K or 4K for a DI production.

The header information within the file at minimum holds the data format, colour space information - linear or LOG, the timecode and tape or reel reference name or number, this is the minimum requirement to conform the data onto a timeline. It is now becoming common for many other details to be within the header data such as key code reference.

One thing to note is that DPX files originally used to have six padded numbers, which in essence referred to unique timecode, some systems still use this but more commonly they refer to the header details for conforming the data.


Usually a project will be over scanned to allow handles for these errors. When comparing against the offline, you should check the first and last frame of every edit. Not doing so can also cause issues, especially if the editor has been using trick effects to make something fit a particular sequence (this will be discussed in effects).

Every shot may need to slip by a frame or two to adjust for these anomalies. Another thing to note is that the editor may have sent you an older version of the edit and you have the newer EDL, which looks slightly different. Yes there are many pitfalls you can find yourself in but being aware of them can infinitely help with completing the project. I’ve never been involved in one project where the edit has matched the offline comparison fully and it’s usually due to very simple editorial decisions – however ultimately you need to be able to also reproduce these tricks to match the offline as best you can.

Also speed changes (M2 commands) need to be over scanned to allow for the extra frames needed to produce the slomo or speed increase. It should be understood that complex speed changes may need to be undertaken by other equipment, as sometimes profiles and interpolation techniques can go look out of place using film material - you should note that there will always be a situation that may work on a small editors screen but will ultimately not work on frame based material projected at 2K.

The re-emergence of online - High Definition Television

With the introduction of high definition television, the online edit has become prominent again. Massive storage requirements of HD have resulted in editor’s off lining in standard definition (SD) then conforming in high definition and mastering from this final timeline.


What is an EDL

An Edit Decision List or EDL is a way of representing a film or video edit. It contains an ordered list of reel and timecode data representing where each video clip can be obtained in order to conform the final cut.

EDLs are created by offline editing systems, or can be paper documents constructed by hand. These days, linear editing systems have been superseded by non linear editing systems which can output EDLs electronically to allow auto conform on an online editing system - the recreation of an edited programme from the original sources (usually video tapes) and the editing decisions in the EDL. They are also often used in the digital video editing world, so rather than referring to reels they can refer to sequences of images stored on disk.

Some formats, such as CMX3600, can represent simple editing decisions only. Both XML and the Advanced Authoring Format are relatively advanced file formats that can contain sophisticated EDLs.


Linear editing systems cannot dissolve between clips on the same tape. Hence, one of these clips will need to be dubbed onto a new tape. EDLs designate these occurrences by marking such dissolves' source reels as b-reels. For example, the EDL will change the 8th character of the reel name to the letter B.

However, sometimes editors will (confusingly) use the letter B to designate timecode breaks on a tape. If there is broken timecode on a tape, there will be two (or more) instances of a particular timecode on the tape. When re-capturing, it can be ambiguous as to which timecode is the right one. The letter B may indicate that the right timecode is from the second set of timecode on the tape. (Confused yet? You will be!!)

EDL incompatibilities and potential problems

EDL formats such as CMX, GVG, Sony, Final Cut Pro, and Avid are similar but can differ in small (but important) ways. Particular attention should be paid to reel naming convention. On the Avid, reel names can be up to 15 characters, but only the first 8 are unique. On FCP (Final Cut Pro), in CMX3600 format, only six characters are allowed. Particular attention should be paid towards b-reels. If the EDL dissolves to the same reel, reel names should be limited to 7 characters since the 8th character may be replaced.

EDLs can use either drop-frame or non-drop frame timecode, running at 23.98, 24, 25, 29.97 or 30fps. Overall, EDLs are still commonly used as some systems do not support other more robust formats such as the emerging AAF and XML formats.


The point is that these many different idiosyncrasies between EDLs will effect the conform for the Digital Intermediate. Simply because the material you will be using will be scanned and not from tape, per se. The material must have the necessary information within its header data, at minimum the files will need the source timecode and tape info (reel number) for the conform to work without holes – also something to note is that with the many different frame rates that you can be working with a frame speed is not represented within the EDL and if you get 30 fps mixed up with 25 fps, you may not have enough handles to cover the length of the edit.

Whether this happens across a network or within a designated set of drive disks, it is essential that the material is available and has the correct number of frames. Otherwise at minimum you will conform and if not correct you will be left with a hole in the timeline.


The Advanced Authoring Format (AAF) is a professional file interchange format designed for the video postproduction and authoring environment. AAF was created to help address the problems of multi-vendor, multi frame rate, cross platform interoperability for computer-based digital video production. AAF does a number of things:

  • Allows complex relationships to be described in terms of an object model.
  • Facilitates the interchange of metadata and/or program content.
  • Provides a way to track the history of a piece of program content from its source elements through final production.
  • Makes downstream rendering possible (with appropriate equipment).
  • Provides a convenient way to "wrap" all elements of a project together for archiving.

By preserving source referencing, and abstracting the creative decisions that are made, AAF tries to improve workflow and simplify project management. AAF's rich data model combining metadata and various types of essence has led to its use in non-broadcast applications as well.

Cross platforming can still be a problem as some manufacturers still have instil their own data, sometimes referred to as ‘dark meta data’ that can only read between its own platforms. This inherently goes against the fundamental idea of how AAF, which has a set structure will allow different machines to work seamlessly with each other.


EDL - an insight to the working EDL


Multi Layered Timelines

Basically a multi layered timeline is exactly that, several video layers stacked on top of each other. A lot of editors use this technique to view different edited scenarios and also to perform effects such as multi camera work or effects that composite through the layers to form a single image that we view. A lot of editing software works with several video layers in real time, the top one being the one shown on the output monitor. Lots of effects can also be treated in real time, thus not rendering or committing the effect, this is all very well and simple of a linear compressed image at 720x576 pixels, possibly using fields as well!!

The problem with these techniques which will be discussed in effects, is that some DI equipment only work with a single timeline or video layer. So providing an EDL with a multiple timeline can pose problems in the conform for these post houses. You may be asked to supply an individual EDL for each video layer, this will then need to be conformed independently, thus creating several timelines that need putting together. The effects that were so simple in the editing process can start to become quite complicated and time consuming. When you transfer the same ideals or settings and try to make it work on logarithmic 2K material, this could be assumed to be a proper visual effect - this is something to bear in mind or become familiar with.


Offline Comparison - The Ultimate Check

Offline comparison is absolutely essential when checking against the conformed material. Errors in data can be checked, such as timecode errors against the keycode, the offline editor may have entered a tape name incorrectly therefore the wrong material may not be able to be sourced leaving temporary holes in the edit. However with the offline edit material you have a visual reference that can at least be looked at to find the source material. Plus simple effects that may not be shown such as horizontal flops will be easily seen.

Something to note is that editors seem willing to ignore frame inaccuracies, as it does not indirectly affect them! Plus not noting timecode break which can also affect the scanning process. Usually when the conform enters the DI lab, the editors job is pretty much done and they may have already cleared their Avid and moved on to their next project. However you should realise– the EDL is only as good as the person who entered the original data into the edit suite. The EDL is pretty much a glorified database, holding information pointing to the correct frames on the film negative. Names have to be entered correctly and the tape checked for accuracy, the pool list is the final list for the scanning procedure and if their are holes and anomalies it can be a painful process and lets face it, the editor does not care at this stage, it is not their problem.

I have seen on one project alone a multitude of errors, the film rested on 80 separate tapes, a frame inconsistency of up to 5 frames over all of them!! In actual fact this was not the editors fault at all, when I finally tracked down where the inconsistency was happening, it was all the way back in the Telecine suite. A new digital routing system had been employed and depending how far from the Telecine the Digi Beta was (a long cable run), a frame error was being introduced on layout to tape. Anything above tape deck 5, introduced an increment of another frame error. Therefore tape deck 6, led the first frame down at 10:00:00:01, deck 7 at 10:00:00:02 and so on, an interesting quandary.