transcode: add comments on why we check frame dropping on 2 places
transcode: add comments on why we check frame dropping on 2 places

krichter722/vlc,krichter722/vlc,shyamalschandra/vlc,xkfz007/vlc,xkfz007/vlc,shyamalschandra/vlc,vlc-mirror/vlc,jomanmuk/vlc-2.2,shyamalschandra/vlc,krichter722/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.2,jomanmuk/vlc-2.2,vlc-mirror/vlc,xkfz007/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc,jomanmuk/vlc-2.2,xkfz007/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc,krichter722/vlc,krichter722/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,shyamalschandra/vlc,vlc-mirror/vlc,vlc-mirror/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc,shyamalschandra/vlc,shyamalschandra/vlc,krichter722/vlc,krichter722/vlc