Update LibAV link to point to GitHub repository

Partial follow-up of #209

Author: frans-ebu

README.md

@@ -190,7 +190,7 @@ A curated list of amazingly awesome open source resources for broadcasters.
 * [Kelvinadon](https://github.com/Streampunk/kelvinadon) - Node.JS pure Javascript module for streaming MXF files to and from JSON.
 * [KFR](https://www.kfrlib.com/) - Fast, modern C++ DSP framework, DFT/FFT, Audio resampling, FIR/IIR, Biquad, EBU R 128.
 * [L-SMASH](https://github.com/l-smash/l-smash/) - A rigidly spec-compliant ISOBMFF library, which has full DASH muxing support.
-* [LibAV](https://libav.org/) - Open source audio and video processing tools.
+* [LibAV](https://github.com/libav/libav) - Open source audio and video processing tools.
 * [libbw64](https://github.com/ebu/libbw64) – Header-only Broadcast Wave 64 (ITU-R BS.2088) C++11 library.
 * [libear](https://github.com/ebu/libear) - A C++11 library to render ADM content according to Recommendation ITU-R BS.2127.
 * [Libebur128](https://github.com/jiixyj/libebur128) - A library that implements the EBU R 128 standard for loudness normalisation.