I have read a draft of iso13818-7, and have no idea about it.
any reply will be appreciated.
thanks.

woo... Nobody answers...
What I want to ask is about dual mono object.
will a dual mono object will be encoded as two SCE,
or one CPE, or one SCE with one CCE?

SCE ---- single_channel_element
CPE ---- channel_pair_element
CCE ---- coupling_channel_element.

regards

The best thing is to encode dual mono as two separate SCE, or in some circumstances as one CPE - but with disabled M/S, IS and other joint channel tools.

CCE is used for multichannel encoding.

The multilingual part is encoded using a coupling channel, which are mixed in a normal channel (SCE or both channels of a CPE). This means that you can for example encode 10 CCE's in 10 different languages and chose which one to mix into the audio channel. Hence, you'll have a multi language audio.
But from your second post I guess that that is not really your question. Dual mono can be encoded using a CPE with common_window = 0, this assures that both channels are encoded completely seperate, but the decoder will know that the channels belong together.

Menno