Log Message:
ffmpeg4: updated to 4.2

version 4.2:
- tpad filter
- AV1 decoding support through libdav1d
- dedot filter
- chromashift and rgbashift filters
- freezedetect filter
- truehd_core bitstream filter
- dhav demuxer
- PCM-DVD encoder
- GIF parser
- vividas demuxer
- hymt decoder
- anlmdn filter
- maskfun filter
- hcom demuxer and decoder
- ARBC decoder
- libaribb24 based ARIB STD-B24 caption support (profiles A and C)
- Support decoding of HEVC 4:4:4 content in nvdec and cuviddec
- removed libndi-newtek
- agm decoder
- KUX demuxer
- AV1 frame split bitstream filter
- lscr decoder
- lagfun filter
- asoftclip filter
- Support decoding of HEVC 4:4:4 content in vdpau
- colorhold filter
- xmedian filter
- asr filter
- showspatial multimedia filter
- VP4 video decoder
- IFV demuxer
- derain filter
- deesser filter
- mov muxer writes tracks with unspecified language instead of English by default
- add support for using clang to compile CUDA kernels