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Appendix B: H.264 Advanced Settings
124 ViewCast
Settings
Setting
Explanation
BitRateTolerance
Setting the bit rate tolerance tells the encoder it must hit the
target bit rate almost exactly. However, this value can have an
adverse effect on quality because you are forcing the encoder
to stay at a target bit rate. More heavy frames may not get
enough bits to make the image look better while less heavy
frames get more than they need. As a result, the quality may
vary. If you set the value to 1, the encoder uses 0.01.
DirectMVPrediction
The default setting is temporal. Temporal breaks when b-
pyramid is applied. As a result, it is easy to mix the two
improperly. Spatial is a better default.
GOPSize
This value sets the maximum interval between IDR frames.
Theoretically, higher values improve compression because IDR
frames are the heaviest, but it can also reduce the appearance
of fluctuating quality.
GOPSizeMin
This value sets the minimum length between IDR frames. This
setting limits the minimum length after each IDR frame before
another can be placed.
InLoopDeblockingFilterAlpha
This value affects the overall amount of deblocking applied to
the picture. Higher values deblock more efficiently, but retain
less detail causing the image to appear softened.
The default value is 0 and should be sufficient to eliminate
most blocking, but it leaves the picture noticeably blurrier. In
general, values should be no lower than -3 and no higher than
3. This value is the most important parameter in determining
the overall sharpness of your encode.
InLoopDeblockingFilterBeta
This value determines whether something in a block is a detail
or not when deblocking is applied to it. Lower values apply less
deblocking to more flat blocks with detail present and more
deblocking to blocks without detail. Higher values cause more
deblocking to be applied to less flat blocks with details
present. Raising the value of Beta deblocking is a good way to
get rid of ringing artifacts by applying more aggressive filtering
to blocks that aren’t very flat. Lowering the value of Beta
deblocking is a good way to reduce the amount of DCT blocks
without blurring the entire picture.
MotionEstimationMethod
This value sets the quality. It determines the motion detection
method (5 is dia, 7 is hex, 8 is umh, 2 is esa, 10 is teas).
Because teas (10) is not really achievable in real time encoding
there is no reason to use it.
dia – (diamond) is the simplest search. It starts at the best
predictor, checks the motion vectors at one pixel upwards,
left, down, and to the right, chooses the best, and repeats the
process until it no longer finds any better motion vectors. This