Grass Valley PDR v.2.1 - Manual (Page 95)

Setting Compression Presets
Profile Family 79
- Min Lum Q sets the minimum compression that can be applied to
luminance in a field to meet the target data rate, typically 0.75, which is
the lowest rate.
- Max Chroma sets the maximum compression that can be applied to
chrominance in a video field to meet the target data rate (typically 60).
- Fixed Q sets a fixed picture quality and ignores variation in field size. Use
this mode for critical multigeneration work. When Fixed Q is selected, the
other fields become fixed as Lum Q (fixed luminance compression) and
Chroma Q (fixed chrominance Q). Useful starting values for Fixed Q and
Chroma Q are 5.00. Verify that there is sufficient available data rate
headroom before using Fixed Q mode. The Bytes/Field target attempts to
meet the Lum and Chroma goals. With Fixed Q mode, Bytes/Field can
increase beyond the system bandwidth, causing interference with other
channels.
- Bytes per Field is the target compression rate. Not every field requires the
target rate, it is simply the average rate the disk recorder tries. The higher
the rate, the better the picture detail. The actual
Bytes/Field depends on the
picture complexity, Min Lum Q , and Max Chroma . The algorithm
dynamically changes Min Lum Q and Max Chroma to make the field size
meet the target unless Fixed Q is selected.
3. Click OK when complete.