ScreenFlow User Guide | Media Capabilities — MPEG-1 Audio
| Audio may not play Some old types of MPEG movies (.mpg, .m1v) may not play audio in ScreenFlow. This is a well documented issue with QuickTime (which ScreenFlow uses for playback of MPEG). Workarounds Convert the media into a different type (such as MPEG-4). Try a codec helper such as Perian (http://www.perian.org), which lets QuickTime play a myriad of normally unsupported file formats.