Audio & Video Licensing for free media player software?

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I'm currently in the process of developing a new multimedia player. The objective of this application is to play almost all audio and video file extensions (MP3, MP4, WMA, WMV, MPG, AVI, ...etc) free of charge. But what confused me and slowed down the development process is the playback-licensing. I Googled my question but still no answers for it. I only found licensing fees for commercial products (the ones that manufacturers get paid for) but no one discussed licensing free players. Please help me because I extremely need this. Thanks