difference between internal and external player

ReplayGain is an extremely useful feature, and here is why:

your reason for wanting to use ReplayGain), it's something that could be considered for a future release if enough other people want it compared with the amount of work that would be required to achieve it. If you can tell us what the functionality is that you require (i.e. Unfortunately, once you've shared something (in this case, an audio file) the sending app doesn't even know which app received it (in the same way that if you share a photo from your gallery, the gallery has no way to know which application you chose to receive the photo - it could be Facebook, Twitter, gMail, Evernote, etc.), and the sending app relinquishes all control of it. The interaction with all external players is achieved using Intents (the same Android feature that allows you to share information from one app to another using a Share button in those apps that support it). external is that internal means built into the operating system, and external means using a separate app, so it's not possible to simply redefine another player as internal.

Difference between internal and external player