API changes, most recent first:
+2018-01-xx - xxxxxxx - lavf 58.7.100 - avformat.h
+ Deprecate AVFormatContext filename field which had limited length, use the
+ new dynamically allocated url field instead.
+
+2018-01-xx - xxxxxxx - lavf 58.7.100 - avformat.h
+ Add url field to AVFormatContext and add ff_format_set_url helper function.
+
+2018-01-xx - xxxxxxx - lavf 58.6.100 - avformat.h
+ Add AVFMTCTX_UNSEEKABLE (for HLS demuxer).
+
+2018-xx-xx - xxxxxxx - lavu 56.9.100 - aes_ctr.h
+ Add method to set the 16-byte IV.
+
+2018-01-xx - xxxxxxx - lavf 58.5.100 - avformat.h
+ Explicitly make avformat_network_init() and avformat_network_deinit() optional.
+ If these are not called, network initialization and deinitialization is
+ automatic, and unlike in older versions, fully supported, unless libavformat
+ is linked to ancient GnuTLS and OpenSSL.
+
+2018-01-xx - xxxxxxx - lavf 58.4.100 - avformat.h
+ Deprecate AVStream.recommended_encoder_configuration. It was useful only for
+ FFserver, which has been removed.
+
+2018-01-xx - xxxxxxx - lavfi 7.11.101 - avfilter.h
+ Deprecate avfilter_link_get_channels(). Use av_buffersink_get_channels().
+
+2017-xx-xx - xxxxxxx - lavr 4.0.0 - avresample.h
+ Deprecate the entire library. Merged years ago to provide compatibility
+ with Libav, it remained unmaintained by the FFmpeg project and duplicated
+ functionality provided by libswresample.
+
+ In order to improve consistency and reduce attack surface, it has been deprecated.
+ Users of this library are asked to migrate to libswresample, which, as well as
+ providing more functionality, is faster and has higher accuracy.
+
+2017-xx-xx - xxxxxxx - lavc 58.9.100 - avcodec.h
+ Deprecate av_lockmgr_register(). You need to build FFmpeg with threading
+ support enabled to get basic thread-safety (which is the default build
+ configuration).
+
+2017-12-xx - xxxxxxx - lavu 56.7.100 - cpu.h
+ AVX-512 flags added.
+
2017-xx-xx - xxxxxxx - lavc 58.8.100 - avcodec.h
The MediaCodec decoders now support AVCodecContext.hw_device_ctx.