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Niagara 2120 User Guide
ViewCast 85
Setting
Explanation
6 — RD on I/P frames
7 — RD on all frames
8 — RD refinement on I/P frames
9 — RD refinement on all frames
10 — QP-RD (requires trellis=2, aq-mode >0)
QuantizerMax
The default setting is 31. This value sets the maximum for the
quantizer. 51 is the highest quantizer available for use in the
H.264 specification and is very low quality.
IMPORTANT! For low bit rates you want to keep constant, it
is recommended that you use the default setting of 51 and not
31.
QuantizerMaxDiffBetweenFrames
This value determines the maximum change quantizer
between two frames. The purpose is to reduce the possibility
of any large quality jumps in the output video. It is better to
slow this change over a few frames rather than all at once. 4 is
good, however if you don’t want to see big jumps in bit rates
and don’t mind big jumps in quality, you can increase the
value to 8 or 16.
QuantizerMin
This value sets the minimum quantizer you will ever use. The
lower the quantizer the closer it is to its input. For most video,
anything below 10 is perceptually lossless. Anything below the
default of 8 is definitely lossless.
IMPORTANT! Raising gpmin higher than its default of 16 is
strongly discouraged because this could reduce the quality of
flat background areas of the frame.
QuantizerScaleCompress
The default setting is 0.60. Use this value to trade off the
number of bits allocated to “expensive” high-motion versus
“cheap” low-motion frames.
At one extreme, a setting of 0.0 aims for true constant bit
rates. Typically with high-motion scenes, this setting tends to
look bad. If you use low bit rates, however, low motion scenes
appear perfect but use more bits than needed.
The other extreme setting of 1.0 aims to achieve constant
quantization, however this setting throws many bits at high-
motion scenes, and a lot less at low-motion scenes which can
cause the bit rate to fluctuate. 0.50 performs well on sports,
0.60 on action content, while 0.30 works well with news
broadcasts. 0.2 works well with drama-type movies, soap
operas, and shows.