Apple Compressor (4.0) - Manual (Page 160)

Chapter 7 Advanced functions 160
Noise Removal
Reduces random flecks of noise from the image. Some codecs introduce noise into the video file,
which can be softened with the Noise Removal filter. You can improve image quality and spatially
compress your material more efficiently by reducing its fine detail.
The noise reduction filter allows you to blur areas of low contrast while leaving high-contrast
edges sharp. This is known as adaptive noise reduction. The results are imperceptible to the
human eye but improve the final compression of the source media. It’s especially important to
use this filter with live video.
The Noise Removal filter contains the following controls:
•
Apply To: Choose the channels from which you want to filter noise using this pop-up menu.
The default choice is All Channels, which filters out noise from all channels including the
alpha channel. The other choice is Chroma Channels, which filters out noise only from the two
chroma channels—U and V—in the AYUV color space (or R408 in Final Cut Pro terminology).
•
Iterations: Choose the number of noise-smoothing passes (between 1 and 4) from this pop-up
menu. For instance, if you choose 2, the noise-removal algorithm is applied to the media file
twice. The modified image is used each time as a starting point for the algorithm. The more
iterations used, the fuzzier the image becomes.
•
Algorithm: Choose a noise-smoothing algorithm from this pop-up menu. Average modifies
each pixel’s color by taking an average of pixels around it, including its own color value.
Replace modifies each pixel’s color by taking an average of pixels around it, while ignoring
its own color value. Merge modifies each pixel’s color by taking a weighted average of
surrounding pixels and itself (with the pixel’s own color value given greater weight).