Exchanging video files between different computers, operating systems and editing software can be frustrating and difficult, yet this task is sometimes necessary.  This can be something as simple as transferring video footage to someone for editing or it may involve collaborative editing where multiple editors are involved with each using different systems and editing software.  Larger in-house operations usually use a common set of editing tools to simplify project collaboration.  However, when independent editors are involved, this task is more complex because of the different computer platforms and editing software that are likely to be used.  The purpose of this paper is to define the best practices for this and to provide easy and understandable procedures for exchanging video files between systems while, at the same time, avoiding damaging or reducing the quality of the video files involved.

The scope of this paper includes definitions of video elements, files and systems only to the extent necessary for clear understanding of the issues involved without unnecessary technical detail that might bog down the clarity of the procedural information that is described.

The process of video encoding begins in cameras where a couple of challenges must be dealt with by the camera manufacturers.  The first is the size of uncompressed or raw video.  Uncompressed raw video is impractical to handle.  Very large file sizes and extremely high data rates make raw video too unwieldy to use.  The second problem is that raw video is simply a stream of video with no file structure.  Raw video streams can’t be handled in computer systems because computers are structured to handle files, not raw video streams.  For this reason, video files are sometimes referred to as containers or wrappers.  As an example, a refrigerator has shelves that are designed to hold containers of food.  But it would be a real mess to open your refrigerator and just toss in unpackaged food.  It would quickly become a foul jumble with no order to anything.

The first step in ‘taming’ raw video begins in the camera.  In order to reduce the size and data rate of raw video, the camera compresses the video when it stores it on the media in the camera.  This process is defined and controlled by a codec (coder / decoder).  A codec is an algorithm that defines and controls the video stream compression.  This compression is not a good thing, even though it’s a necessary thing, because it damages the video stream with unavoidable compression artifacts.  The key objective for a well designed codec is to minimize the amount of visible damage to the video stream while achieving the objective of reducing the video’s size and transfer rate to a more manageable level.  The objective is to minimize visible damage to the video when viewed.

Tape based HD camcorders use various codecs that were defined by the Motion Picture Experts Group called MPEG.  Since unstructured video steams can’t be handled by computer systems, a file structure is applied when the encoded video is captured or transferred to a computer.  

For example, HDV video is organized into a file structure called .m2t.  These .m2t files have the necessary structure for a computer system to handle.  This file structure defines its size, the elements and locations of the content in the file and a key piece of information that specifies the codec that is required to open or play the video and audio content of the file.  Just as a codec defined the compression algorithm when the video was compressed, it also defines the decoding process that is necessary to open or play the video.  

Without the codec that matches the codec that was used to initially encode the video and audio content of the file, it can’t be opened or played.  Since video files are just containers for the video streams within, they can contain a wide variety of encoded video.  To simply describe a file as an .avi or .mov file for example, says nothing about the codec used to encode the video stream within it.  It’s a bit like coming home from the supermarket and announcing that you have a bag.  That’s nice, but what’s in the bag is more the matter of interest.  “It’s a bag”, isn’t a very good answer when someone asks, “What’s for dinner?”  So when someone tells you they have a .mov or .avi file, they are just telling you they have a bag in this analogy; they aren’t telling you the type of video they have in the file.

Opening or playing a video file is the first stage where problems may be encountered.  One problem is that the codec required to open the file may need to be installed on the host system, but installing the required codec is easy enough to do.

The second problem is more complex.  This is especially true with memory chip based video cameras that use newer and more sophisticated codecs.  The problems are the different file types that the camera manufacturers chose to ‘contain’ the video streams as well as the different codecs that are used to compress the video.  Unfortunately, among the various camera manufacturers, there are a wide variety of file types and codecs that are used.  There is a lack of standardization due in part to competition between the camera manufacturers.  Each manufacturer wants to develop the ‘best’ codec and keep it proprietary for competitive advantage.

Computer systems can’t handle file types that weren’t designed to work with their file handling protocol.  Although there are many file types used to contain video, the ones most commonly used are .mov, .avi, .m2t, .m2ts and MP4 files.   .mov files were designed for use on Apple systems although QuickTime can be installed on a Windows PC’s which allows .mov files to be opened on PC’s as well.  However, .mov files may behave unpredictably on a Windows PC and most people avoid using .mov files on a PC when possible.   .avi files were designed for use on Windows PCs and may not always work correctly on Mac systems.  .m2ts or MP4 file types are often used to contain various AVC codecs such as AVCHD and AVC H.264.  (AVC is an abbreviation for Advanced Video Coding.)  Unfortunately there are a number of variations of AVC codecs.  AVC is relatively new and various ‘improvements’ continue to be made.  To minimize problems, it’s a good idea to use the software utility that came with the camera to transfer the footage to your computer; that is unless you enjoy the ‘recreational misery’ that comes with directly transferring the files from the camera’s memory chip.  These software utilities can handle the proprietary codecs that are often used as well as seamlessly ‘stitch together’ the video file segments.

The key thing to remember is that .avi, .mov, .m2t, .m2ts and MP4 files are NOT codecs; they are simply ‘containers’ or ‘wrappers’ for the video streams inside.  Transport streams such as .m2ts are structured into packets to allow these streams to be transmitted using data transmission protocols.  A transport stream refers to the packet structure of the stream(s), not the ‘quality’ of the codec used to create the streams.  Players, such as Blu-ray, that were designed to handle transport streams can play them; however, the transport streams are still ‘contained’ in video files because the players cannot handle raw streams.  These .m2ts transport streams are put into BDMV or BDAV files for use in Blu-ray players.

No given file type is ‘better’ than the other.  Each is designed to follow the ‘rules of the road’ for file handling in the respective computer systems or players for which they were designed.  Because of this, it is sometimes necessary to convert video files from one file type to another so that they may be opened on a given computer system.  Dealing with the issue of converting from one file type to another is the first opportunity to do things rightly or wrongly.  First, the wrong way - reencoding.  This is done by loading the video file into an editor and rendering (exporting) the file into the file type and codec that is to be used on the destination system.  This should never be done.  This is an area where bad advice is often given from the “It’s good enough” crowd or blowhard advisors.  Don’t listen to it; it will reduce the quality of the video.  Unnecessarily reencoding video damages it  – always.  The only way this file type conversion should be done is to ‘rewrap’ it.  

Rewrapping doesn’t reencode the video stream therefore it doesn’t damage the quality of the video.  There are various programs that can be used for converting to or from .avi or .mov files.  

Among them are:

Avidemux - http://avidemux.sourceforge.net/ - PC

FFmpeg -   http://ffmpeg.org/ - PC or Mac

QuickTime Pro - http://www.apple.com/quicktime/ - PC or Mac

MPEG StreamClip - http://www.squared5.com/ - PC or Mac

Refer to the respective documentation on these products for usage procedures.

There are a few codecs that aren’t supported in both .avi and .mov wrappers, e.g. the Lagarith codec can be used in an .avi file but not a .mov file.  Fortunately this is an unusual situation that isn’t likely to be encountered with the codecs that are normally used for editing.  In the event you have a video file that contains a codec that can’t be used in another file type, you can also do a lossless export from your editor.  This is best for small clips because the file sizes with uncompressed video are very large.

Cameras that use memory chips utilize a software program which comes with the camera that puts the video into the appropriate file type as required for the system on which the video will be edited.  It is best to use this software rather than drilling down into the folders on the memory chip and copying the video files directly.  For example, Sony XDCAM EX cameras use Sony’s Clip Browser, a free software utility provided by Sony.  http://bit.ly/7jUsBn  It can save some major frustration if you use Clip Browser for its intended purpose.  Sony also has a convenient XDCAM Transfer Plug-In for Final Cut Pro http://bit.ly/85cd95   The efficaciousness of the video transfer utility applies to other cameras as well.  If you don’t have the camera’s transfer utility, you can download it from the camera manufacturer’s web site.

A good way to deliver EX1 or EX3 footage to someone is to advise them to download Sony’s Clip Browser and have them transfer the video from your memory chip(s) into the file structure they need.  If you don’t want to hand over your memory chips to someone, you can copy the chips’ content to a hard drive and Clip browser can still be used.  If you transfer the content to a hard disc drive, it is VERY important to copy the BPAV top-level folder and all its content so that it will work with Clip Browser.  If you prefer to export the video files from Clip Browser yourself, make sure that it is the correct file type for the system on which the files will be used.  No offence to some clients but they simply may not know the correct file type that they need.  To simply say, “It’s an .avi file” for example isn’t enough information.  To be safe, it’s a good idea to retain the original video content until you are sure that the transferred footage is in the correct format for use.

A somewhat related issue is sharing video which you are editing with someone who uses a system or editing software that is different from yours.  The first, and most desirable, are editing workgroup configurations that are deployed in larger companies.  These configurations are outside the scope of this paper.  The intent of this paper is to suggest ways to casually exchange video data between people who use different systems and NLE’s without unnecessarily damaging the video in the process.

NLE developers manage to include in their new releases many temptations to upgrade to their latest versions.  Among these features are tools to facilitate sharing  video projects with users of other NLE’s.  For example, Premiere Pro CS5 has tools that simplify sharing video projects with Final Cut Pro, AVID and several other editors.  When a need arises to transfer video clips to another editing environment, it’s worth investigating the capabilities of your editor to determine if it has the tools that may support this.  You may need to do a little exploring because this is a capability that you may not ordinarily use and therefore you may not be aware that it’s there.  This method is a great first choice for transferring video if you have it available in your editor.

The most important thing to avoid is reencoding video to either a capture or final output codec format.  This is heavy-handed and will unnecessarily damage the video.  These codecs were not designed for intermediate reencoding of video.  Their excessive compression will damage the video with compression artifacts.  Each time video is reencoded, it introduces additional compression artifacts.  The mistake that is often made is, “He or she is using format xyz so I will just convert the video to xyz and give that to them.”  This may seem easy or reasonable but it’s a bit like taking a sledge hammer to their video.  It’s a shame to take beautiful high definition video and run it through a ‘meat grinder.’

If your NLE doesn’t have the tools for transferring clips to another editor to whom you may need to transfer footage, Cineform is a very useful tool for doing so.  Cineform is an independent company that has developed a family of intermediate codecs that are specifically designed for use by video editors.  First, it would be helpful to describe a codec type that is often referred to as an ‘intermediate codec’.  These are codecs that are designed specifically for use while editing video rather than for final output.  They are called intermediate codecs because their file sizes are quite a bit larger than those of a final output or playback codec.  They aren’t completely lossless when reencoding but are nearly so.  As a result they are often referred to as ‘near lossless.’  They are designed to give video editors more options with the things they can do with their workflow in an editing project.  For example, a useful feature of these intermediate codecs is the ability to export (reencode) video clips that can be saved or reloaded into a project.  Since they are near lossless, a given video clip can be reencoded eight or ten times with little or no visible damage to the video.  Examples of intermediate codecs are Apple’s ProRes, Grass Valley’s Canopus HQ  or Canopus Lossless, and Cineform.  ProRes and Canopus HQ are proprietary codecs and don’t work outside their own editing software or computer platform.  Cineform does provide a ‘universal’ solution.

Cineform Codecs are similar to ProRes or Canopus HQ in that they are near lossless codecs that allow multiple reencoding of video with virtually no damage to it.  There are many useful features with Cineform that may be explored on their website –  cineform.com.  The features of Cineform are outside the scope of this paper however.  I will focus on one: the ability to transfer video footage between different computer systems and editors with virtually no damage to video files.

Cineform’s business objective differs from Apple’s or Grass Valley’s (Canopus) in that they are an independent company that targets the entire video editing market for use of their products.  Apple’s and Grass Valley’s intermediate codecs are proprietary architectures that are intended for use with their own editors.  Canopus does provide a way to open Canopus HQ files on a PC but this is not available on MAC systems.  The significance of this is that Cineform provides a universal way to transfer footage between different systems and editors with virtually no loss of video quality.

A major benefit of Cineform is that the reading / playback codec is free.  Cineform provides it at no charge to encourage wide usage of their codec.  It’s analogous to Adobe’s PDF reader which is also free.  Cineform makes their money by selling their encoder just as Adobe makes theirs by selling their PDF file generator.  By providing the reader at no charge, it encourages wider use of their products.  Cineform has various versions of their codec that differ primarily by the extended features that are useful to editors.  The encoding quality isn’t less with their lower priced encoders.  Their least expensive encoder is NeoScene which costs $129.  Both Mac and PC versions are available.  The resulting encoded video is the same with either version so video can be exchanged between either of these systems.

Here is a description of the way video clips may be transferred using Cineform to a different system and/or NLE.    Simply load the clip(s) that you wish to transfer into your editor and encode (export) them using the Cineform codec.  Obviously you will need to buy it if you don’t already own it.  This output is a near lossless version of the clip(s) and is encoded with the Cineform codec.  These clips may then be opened on any computer or editor that has the free Cineform reader installed.  

The free reader can be downloaded from Cineform’s website – http://cineform.com/

To summarize; if you need to convert a video file from one file format to another, use a video file conversion utility that only rewraps the video into the new file type.  It’s important to not reencode the video because of the resulting damage to the video quality that is caused by recompression.

If you need to transfer edited footage or work in process clips to someone else for additional editing, avoid encoding with capture or final output codecs.  This will unnecessarily damage the video.  A good first choice is to use project sharing features in your NLE if available.  Newer NLE versions are more likely to have this capability.  Check your manual as well as other sources of information to verify the availability of this function.  Who know, if this feature isn’t available in your NLE, this may help you justify spending the money that you have been itching to spend on an upgrade.

If work sharing tools aren’t available in your NLE, consider using Cineform as an intermediate codec for this purpose.  This involves spending a little money if you don’t already own Cineform but it is a very useful way to transfer footage without damaging the video quality.  Whatever you do, avoid transferring footage by encoding to capture or final output codecs such as MPEG, HDV. .m2t, .m2ts, WMV et al.  All of these will cause needless recompression damage to the video.