Video Compression for the Web

Submitted by Robert Alstead on Mon, 12/22/2003 - 16:00

If you want to put video on the web or send clips by email then you are going to have to compress it. Full screen, full-frame video files are simply too big for sharing over the web. To get the best results out of compression you want to start off with clean, clear and straightforward footage. Studio-shot talking-head shots may sound boring but these will work best. At the other end of the spectrum are roaming effects-laden footage epitomised by MTV. So with this in mind here are ten tips for enhancing video that you are distributing over the web.

1. Tripod mount the camera
Tripod mounting the camera ensures a steady shot that will compress well. Even steady handheld footage is inevitably more busy, with most of the information in the picture changing from one frame, thereby creating an unnecessary extra amount of work in the compression process. This can result in visual artefacts and noise in the compressed picture.

2. Don't go crazy with the pan and zoom
This is for the same reason that you tripod mount the camera: you want the picture to be as consistent from one frame to the next to get the best compression. So if shooting an interview, just set the camera up on a tripod, frame the subject and roll with minimum camera movements for best results (technically, if not creatively speaking, at least).

3. Light it up
This could be as simple as flicking a light switch or two in the room, or moving the subject into an area that is better lit - like outside. Avoid fluorescent lighting which can create flicker and use incandescent or flood lights that cover the subject evenly.

4. Listen to the sound
The microphones that come with most camcorders are usually omni-directional, meaning they pick up sound from "all directions". While sometimes "omnis" work for ambient sound, if you are trying to hone in on, say, somebody's voice, it can come across as thin, distant, or even inaudible because it is blocked out by nearby noises. If you do many interviews invest in a handheld cardiod mic, or a lapel microphone (you can get a reasonable one for under £50), or gun mic (more pricey). You should always wear headphones when shooting so that you can be sure you are getting good sound. Try filming in silence - does your mic pick up camera motor noise or the sounds of your fingers as they are working the controls? Clean sound, devoid of background noises, compresses best.

5. Turn auto-focus off
Where possible you should use manual focus. Auto-focus has a nasty habit of focussing on the wrong part of the picture, especially when shooting into a bright, high contrast area where the auto focus starts "hunting" for the subject. All that activity doesn't help in the compression process. A steady, consistent image is best. Are you getting the message yet?

6. Get close
Viewing most video on the web is still through a relatively small window and in spite of advances in compression technology picture detail is lost. Panoramas look much less interesting when squashed into a web window. The camera needs to go that bit closer to be able to see facial expressions at the end of the line.

7. Edit first, compress last
Every time you compress a clip you lose quality. So, where possible, capture footage to your computer and edit your movie uncompressed. Then either export the final edit in your chosen compression format or take the finished uncompressed movie and compress with one of the dedicated encoders (e.g. use Windows Media Encoder to play in Windows Media Player, Real Encoder to play in Real One Player).

8. Avoid complex transitions and special effects
Just because your software program came with 1001 editing effects doesn't mean you have to use them. It's tempting, but if you want to keep your file size down (and therefore your web videos looking good) then keep the special effects to a minimum.

9. Experiment with compression settings
Compression is a trade-off between quality and file size. Try out the different presets that come with your video editing software or encoder and create your own custom settings. See what settings give the best results.

10. Know your audience
Just as important in technical as in creative matters. Try to make sure that your audience has the right player and/or enough bandwidth to view your work. If they don't, make it easy for them to get hold of the right software to play the clip and offer a lower bandwidth alternative for those on slower connections.

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