Tips on how to improve the quality of your video for web or mobile devices
- Amman Filmmakers Cooperative (AFC)
December 5, 2006
HOW TO IMPROVE THE QUALITY OF YOUR VIDEO FOR WEB OR MOBILE DEVICES
With the internet and mobile devices becoming popular methods for the
delivery of video content, a few tips can go a a long way to help
improve the quality of video before it undergoes the necessary video
compression for upload to the web or mobile devices. This article is
published at the Adobe Developer Center.
Capturing Good Video
In addition to the physical properties of your video there are a
variety of factors that affect the efficiency of the encoder and,
ultimately, the user experience of the video playback. Two factors
play a significant role in the encoding process: source quality and
You determine the source quality of your video as soon as you press
the recording button on your camera. The following are some basic
guidelines for getting great source video quality and maximizing
quality in your final compressed video.
Use a tripod to reduce camera movement. If your camera is not steady,
most of the image moves, causing a high percentage of pixels in the
video to change from frame to frame. A steady camera reduces the
number of pixels that change from frame to frame, giving you better
quality at higher compression rates (lower data rates).
Use good lighting techniques. A high-end camera resting on a tripod
can still produce a low-quality image if there is not enough light.
Low-light or light-gain filters produce video noise on the image. This
noise is different for each frame of video and makes it difficult for
the codec to compress the file at a good quality. You may need to use
or exceed your maximum data rate to compensate for video noise.
Use the best camera possible. Low-grade cameras specifically
consumer-based ones that record an analog signal on magnetic tape
(VHS, Hi-8, and so on)produce much video analog noise. Still digital
cameras in movie mode also have limited quality and generally produce
high-noise video clips. Even if the camera is on a tripod, with
excellent light, it will produce noise.
Do the best you can with what you have to work with. High-end digital
cameras, digital Betacam camcorders, and 35mm film cameras produce a
clean image if the scene is well-lit and they are stabilized by a
tripod. Such a scenario produces the best compression ratio and lets
you reduce the data rate while maintaining excellent quality. However,
you may not have access to professional equipment, a tripod, and
excellent lighting conditions. Just remember: the higher the quality
of your video source, and the less noise in that source, the lower the
data rate required to render a good playback file.
Whenever possible, always encode a file from its uncompressed form. If
you convert a precompressed digital video format into the FLV format,
the previous encoder can introduce video noise. The first compressor
has already performed its encoding algorithm on the video and has
already reduced its quality, frame size, and rate. It may have also
introduced some of its own digital artifacts or noise. This additional
noise affects the FLV encoding process and may require a higher data
rate to play back a good-quality file.
Frame motion is another factor to consider in your encoding formula.
It is the percentage of the pixels that change from one frame to
another. This change can result from a person or object moving, camera
effects, or post-production effects, such as the following:
* People and objects moving can include someone walking past the
lens, tree leaves blowing in the wind, cars driving by, or an extreme
close-up of a face.
* Camera effects such as camera panning, zooming, or hand-holding
result in almost 100% pixel change from frame to frame.
* Postproduction effects such as dissolves, fades, wipes, or
complex video effects result in a high percentage of pixel changes
from frame to frame.
The greater the motion within your video clip, the more information
the encoder has to compress. If your clip is relatively still (such as
a talking head video), there isn't much pixel change from frame to
frame. The video compressor uses a method of dropping frames and then
encoding a series of fully uncompressed frames. These uncompressed
frames, called keyframes, are used to calculate and "rebuild" the
missing frames during playback.
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Copyright 2006 Adobe Systems Incorporated. All rights reserved.
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