update doc
update doc

leohdr/mixer,fengshao0907/mixer,leohdr/mixer,shenli/mixer,shenli/mixer,flashbuckets/mixer,maxencoder/mixer,fengshao0907/mixer,maxencoder/mixer,flashbuckets/mixer,siddontang/mixer,deafgoat/mixer,deafgoat/mixer,siddontang/mixer