[M4IF Technotes] brightness change for sprites

[Yoshinori Suzuki]

Dear Dr. Binder,
axel.binder   philips.com wrote:
> 
> I have a question about the brightness_change_factor in 14496-2 Amd.1 in
> chapter 7.8.6.
> 
> In the spec this factor is defined for the Y channel for static sprite and GMC
> sprite decoding, right?

Sprite (static and low-letency) decoding only supports this factor.
> However in the reference code (14496-5 from ISO) I couldn't find it's usage
> during decoding neither in the
> Microsoft nor in the MoMuSys implementation. It is encoded to the stream and
> decoded from the bitstream
> but during sample reconstruction it is ignored.
> Now my question: Do I need to take care of this factor for a compliant sprite
> decoder implementation
> or can it be ignored?

You need to take care of it for the visual main profile compliant decoder,
since sprite supports it.
But, you can ignore it for the advanced coding efficiency profile or  
the advanced simple profile compliant decoder, since GMC does not support it.
Best regards,
Yoshinori Suzuki
Hitachi, Ltd.