Originally Published: Tuesday, 5 September 2000 Author: Alex Young
Published to: enhance_articles_multimedia/Video Articles Page: 1/1 - [Printable]

An Introduction to Digital Video Editing

Home video editing with desktop computers has come a long way since simply using a genlock to overlay text and images onto VHS. With consumer level equipment, it is now possible to arrange chunks of DV video (running at 3.6MB/sec), chromakey images with sophisticated 3D special effects, create 2D and stop motion animations, master DVDs and distribute compressed video over the Internet.

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Home video editing with desktop computers has come a long way since simply using a genlock to overlay text and images onto VHS. With consumer level equipment, it is now possible to arrange chunks of DV video (running at 3.6MB/sec), chromakey images with sophisticated 3D special effects, create 2D and stop motion animations, master DVDs and distribute compressed video over the Internet.

DV (Digital Video), which used to be known as DVC, is a consumer video recording format that is set to supersede analogue formats[1]. The main advantage of DV is higher quality pictures and less noticeable degradation from copying. Cassettes are similar to 8mm or VHS-C. Other similar formats include Sony's DVCam and JVS's Digital-S.

A DV camcorder, used in conjunction with a FireWire card, allows footage to be uploaded to the PC for editing. The Linux 1394 Project is an effort to support FireWire under Linux. IEEE 1394 is the standard for this high speed serial bus, featuring transfer rates up to 400Mbits/sec. Currently, The supported chipsets are the Adaptec AIC-5800, Texas Instruments PCILynx/PCILynx2, and OHCI compliant chips. One of the first programs to allow capture from these devices was DV Grab.

It is also possible to use a TV Card to capture video. Most Bt848/849/878/879 cards are supported. However, my Bt878 card uses DMA sound instead of an external cable (like my Hauppage card), which isn't currently supported. Fortunately, the Bt878 card works with Linux 2.4 and the newer lmsensors package. There's also a Video For Linux 2 BTTV driver, supporting Bt8x8 cards, which is under active development. The driver is supposedly alpha quality, but I have had no problems with it after using it for 2 months.

Linux Media Labs have a Bt878 based card specifically for Linux. They primarily offer teleconferencing solutions for Linux, but their products are valuable for video editing too. For example, the LML33 video capture/playback card has hardware compression/decompression for Motion JPG, and can be used with software such as Broadcast 2000 under Linux.

NLE (Non-Linear Editing) gives one great editing power over captured footage. Video footage is edited by moving around clips, and the user can overlay text and sound. The most widely know NLE software includes Adobe Premiere and Ulead MediaStudio Pro. However, there are alternatives for Linux.

MainActor 3.55 is a suite of five programs for editing multi-media videos. With a video capture card, MainActor can be used to clean-up home movies, tile and edit movies using 2D and 3D text, and has plugin support.

The MainActor Sequencer allows clips of animation to be sequenced, along with sound and text objects. However, MainActorVE allows single animations to be edited, allowing single frames to be removed. It can also convert file formats. A possible application of this would be converting a large format, such as uncompressed video, to something more suitable for distribution on the Internet, like QuickTime. There is also a program to facilitate video capture that worked well with my Hauppage TV Card.

MainActor is only available as a RPM, and I tested it under Linux Mandrake. The RPM installed with no problems, although my setup is the stock Mandrake 7.0 CD installation for a workstation. After it installed, I queried the RPM database to view the myriad of files it had extracted onto my system. The capture program worked well after I had used 'insmod' to load the relevant kernel modules for my capture card. After capturing a few minutes of audio/video, I proceeded to test the sequencing software.

All of the MainActor applications feature a clean interface, and the package even has a MainActor help viewer. Sometimes the interface was unresponsive, which left me wondering whether it had crashed or not, however, the package is easy to pick up and would be especially easy for new Linux users to get to grips with.

Another NLE for Linux is Broadcast 2000. Broadcast 2000 boasts editing capabilities including 1920x1080 video and 24 bit sound and colour correction. The potential for enhancing video and sound by using Broadcast 2000 is impressive - graphics can be easily overlayed from packages such as The Gimp, it scales to SMP, audio and graphical effects can be added, etc. The package can also be extended using plugins. Plugins include Gaussian blur, noise reduction and image stabilization.

Another video editing package is Crow NLE. Crow is distributed under the GPL, and uses GTK and has a Gimp-like plugin API. Crow is only available via CVS, and I had major difficulties installing it. First, it required QuickTime for Linux, and then the plugins would not compile.

Crow is comprised of the Crow libraries and various other tools. At the moment, the system is not as complete as Broadcast 2000 or MainActor, but does seem to show potential.

I would recommend MainActor to new Linux users. Broadcast 2000 is clearly an excellent package, but after having problems with the installation it became clear that a newbie would prefer MainActor. However, professional results are definitely possible with Broadcast 2000.

On a slightly different tangent is The Free Film Project, a somewhat ambitious project whose aim is to provide a full suite of utilities to act as a virtual film studio. Currently the project offers four programs: an RGB filter, lighting control software, storyboard utilities and a script writing utility.

I hope this article has informed you of the possibilities for video editing under Linux. It is clear that a lot of work is still required in the field, but hopefully with the continuing growth of many projects such as the Gimp and XFree86, video editing will become more and more feasible for the desktop Linux user. Even if you only have a TV card, get the drivers and have fun splicing catpured footage together - it's surprising what you can do with amusing samples and 60s Star Trek clips.

[1] Computer Video - September 2000





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