5.5

Working with Color Spaces in HD Projects
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For some project formats, the Project Type list lets you change the format of the project to
another format that shares the same frame rate. For example, if you are working in a
1080i/59.94 HD project, you can change the project format to 30i NTSC.
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If you switch from one project type, aspect ratio, color space, or raster dimension to another
during the course of your workflow, you might create precomputed clips that have not
rendered with the quality that you need for your final output. You might need to manually
purge the precomputed clips and re-render effects. For more information, see “Ensuring the
Quality Level of Precomputed Clips” in the Help.
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For 24p PAL projects, the Format tab shows the audio transfer rate you selected when you
created the project. The actual audio transfer rate might be different from the display if you
used the Film and 24P Settings dialog box to change the audio transfer rate.
To open the Format tab:
t Click the Format tab.
Working with Color Spaces in HD Projects
In full HD projects, some Avid editing applications and Avid input/output hardware devices
let you work in either the YCbCr or the RGB color space. Your Avid editing application uses
a project’s color space setting to control how it displays video, processes most effects, and
outputs sequences.
RGB and YCbCr both separate colors into three channels, but they store color information
differently. When you choose which color space to work in, you need to take several factors
into consideration, including the color space of your media, your output needs, and your
performance expectations for your Avid editing application while editing.
The RGB color space is not available for 720p or NTSC/PAL SD projects.
Understanding the YCbCr Color Space
YCbCr performs better, but is of lesser quality.
YCbCr stores brightness (Y) separately from colors (Cb and Cr). Since humans are more
susceptible to changes in light than in color, YCbCr discards half the chrominance data
(one-third of the overall data) with little discernible difference to image quality. Media that
uses YCbCr takes up less disk space than media that uses RGB, and less bandwidth is
required to play it.
YCbCr is the only color space available for SD media, because SD requires lower
bandwidths and might need to maintain backwards compatibility with black-and-white
displays. When you only need SD output, you only need to work in the YCbCr color space.