ADS Technologies USBAV-708 INSTANT VIDEOMPX, Руководство пользователя

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Source pre-processing
In the modern computer age digital video can be acquired from a wide and varied
array of sources. DV Camcorders, DVD video discs, TV capture cards and even
web-cameras have all become so accessible at the consumer level that for DivX
to consistently produce high quality output it is necessary to provide a means of
correcting video issues attributable to particular sources.
Pre-processing allows the encoder to clean phenomena such as noise, grain,
flickering and color inconsistency from the source video prior to encoding it. An
immediate benefit of pre-processing is an increase in the viewers perception of
quality. With respect to encoding, a reduction in noise and general inconsistency
in the texture from frame-to-frame yields a lower bit-spend when encoding the
image because the DCT is less complex and the motion search is more
successful.
Pre-processing is most effective when applied to video taken from an analogue
source - typical examples being VHS tape, TV capture, and camcorder footage.
All of these sources are likely to suffer from noise—high-frequency variations
around the true color of each pixel. Noise
causes the image to appear fuzzy or speckled.
Digital sources are also susceptible to noise.
DV camcorders and web-cameras often
amplify the signal arriving at their image sensor
in low-light conditions, introducing a lot of noise
to the picture. Web-cameras are also notable
for an increase in noise proportional to the resolution, frame-rate and lack of
strong lighting. Even DVD video re-mastered from film can show the fine grain of
the original film media. This particular effect is a special case as it is sometimes
desirable in the encoded video, adding warmth to the picture. DivX includes a
special decoder feature allowing the artificial application of grain to any video,
even when the original grain was removed during encoding.
What is pre-processing?
When to use pre-processing