How to force a file to be MPEG-1, MPEG-2, or MPEG-2.5? 2017-04-25 22:12:45 The three audio compression layers are defined in MPEG-1, MPEG-2, and MPEG-2.5, of which the first two are the official standards, and the third one is proprietary and unofficial.In total, there are basically nine encoding versions, but how can I safely distinguish the nine versions form one another?Even though the MPEG-2.5 standard is not official, I'd be interested in testing it, etc. However, I'm unsure how I can "force" creation of a - say - MP3 file that conforms to that standard.As far as I can tell, the only real difference, is the number of channels, as well as the sampling rate (which seems to be the most deciding factor) as well as the available bitrates. These however overlap, so it's not really possible to tell which one is which, unless one uses a bitrate that is exclusive to either standard.My question however, is more geared towards creation of these files. Suppose I want to use a tool like LAME of ffmpeg, I'm unsure, how to specifically select the MPEG standard, and the layer. I'm either not finding this in the man pages, or is it impossible to select like that? I can only assume, that the sampling rate automatically selects the standard, but I couldn't find anywhere to corroborate that.One additional thing that is kinda murky to me, is whether MPEG-2.5 can be contained in MPEG-ES, the thin container, which is used for most ".mp3" files, etc.