on my macbook air purchased fall 2015.... i have downloaded an app in firefox which allow me to download files. but only gives option of mp4, web and 3gp and even tho says fly option does not show. am only familiar with mp4 which is a video and flv. i have tried to download mp4 and convert mp3 using total video converter lite but quicktime nor flv will open files. i cannot open nor import mp4 into this converter video app. i have tried playing the video in youtube and recording on audacity which works out okay but audio sounds like in a barrel...kind of double audio. any ideas of a work around this?