[XviD-devel] somebody can tell me how to use dquant?

[peter ross]

hi,

On Mon, 27 Dec 2004 09:27:42 +0800 "???" <dengxiongshu at yulong.com>
wrote:
>        Could  anyone tell me how to implement dquant?   how can I use 
>dquant?  If dquant is not equal zero, is current macro's quant
>equal to previous  macro's  quant add current macro's dquant? dquant is

the dquant array is used to vary the level of quantization applied to
each macroblock. the dquant value is added to the overall frame quantizer.
see SetMacroblockQuants() within xvidcore/src/encoder.c. in pseudo code:

	macroblock[n].quant = frame_quant + dquant[n];

important: the mpeg-4 bitstream format restricts the extent to which the
quantizer can be varied. MBSetDquant() within xvidcore/src/encoder.c
takes care of this.

>to use to macro level rate control? xvid have not implement macro level
>rate control,so I don't understand dquant is use in xvid ,it is for
>future?

dquant could be considered an optional feature of xvid. it is only used
if an appropriate plugin is linked to xvidcore. at the moment, we only
have one plugin that uses dquant. see 
xvidcore/src/plugins/plugin_lumimasking.c

regards,
-- pete