What does Bias and DC predic do? (In HC)

[dirio49]

In HCenc !! or any other What is Bias and DC predict?

I am using DVDrb and would like to know what Bias is ? What does it do to the compression of a movie? Does it slow it down? does it increase the quality?
and anything else that is important.

And about Dc predict. What does it stand for? What does it do?


Thanks.

P.S.
Sorry if I am cross posting.

[jdobbs]

Bias makes a determination as to how much swing the bitrate makes. When set higher the compression becomes more like CBR (constant bitrate) and lower it becomes more variable. Too low a setting will not allocate enough bitrate to very low demand areas and you may get blockiness in dark scenes and "fade-to" scenes. Too high and it steals too much of the high demand areas causing similar effects. The default settings are a good balance.

The setting "dc_prec" is the bit precision of the DC coefficient of the intra-block in Intra DC precision. It is normally set to either of 8, 9 or 10 bits.

Here's as good a decription as you might find (from the CCE manual):

In general the optimum settings cannot be determined since changes depend on the details of the picture and movement intensity. For pictures with intensive movement and fine bumps, a low number of bits is appropriate. For smooth pictures with little movement, a higher number of bits is appropriate. A low number of bits may be specified for use at a low bitrate up to 4Mbps, and a high number of bits may be specified for use at a high bitrate.

By default DVD-RB uses the encoder's defaults. These settings are really meant for "experts".

[dirio49]

thank for the fast reply.