ffmpeg (Software to record, convert and stream audio and video)

FFmpeg is a complete solution to record, convert and stream audio
and video. It includes libavcodec, the leading audio/video codec
library.

You can enable a lot of optional (not-autodetected) features by
passing variables to the script (VAR=yes/no ./ffmpeg.SlackBuild):
ASS=yes|no (default: no), requires libass
BLURAY=yes|no (default: no), requires libbluray
BS2B=yes|no (default: no), requires libbs2b
CELT=yes|no (default: no), requires celt
CHROMAPRINT=yes|no (default: no), requires chromaprint
DC1394=yes|no (default: no), requires libdc1394
DECKLINK=yes|no (default: no), requires decklink-sdk
EBUR128=yes|no (default: no), requires libebur128
FDK_AAC=yes|no (default: no), requires libfdk-aac (creates non-redistributable binary)
FLITE=yes|no (default: no), requires flite
FREI0R=yes|no (default: no), requires frei0r
GME=yes|no (default: no), requires libgme
GSM=yes|no (default: no), requires gsm
IEC61883=yes|no (default: no), requires libiec61883 and libavc1394
ILBC=yes|no (default: no), requires libilbc
LADSPA=yes|no (default: no), requires ladspa_sdk
LAME=yes|no (default: no), requires lame
MODPLUG=yes|no (default: no), requires libmodplug
NETCDF=yes|no (default: no), requires netcdf
OPENAL=yes|no (default: no), requires OpenAL
OPENCORE=yes|no (default: no), requires opencore-amr
OPENCV=yes|no (default: no), requires opencv-legacy
OPENSSL=yes|no (default: no), creates non-redistributable binary
OPUS=yes|no (default: no), requires opus
RTMP=yes|no (default: no), requires rtmpdump
RUBBERBAND=yes|no (default: no), requires rubberband
SCHROEDINGER=yes|no (default: no), requires schroedinger
SNAPPY=yes|no (default: no), requires snappy
SPEEX=yes|no (default: no), requires speex
TESSERACT=yes|no (default: no), requires tesseract
TWOLAME=yes|no (default: no), requires twolame
VIDSTAB=yes|no (default: no), requires vid.stab
WEBP=yes|no (default: no), requires libwebp
X264=yes|no (default: no), requires x264
X265=yes|no (default: no), requires x265
XVID=yes|no (default: no), requires xvidcore
ZMQ=yes|no (default: no), requires zeromq
ZVBI=yes|no (default: no), requires zvbi

Additional optional (autodetected) dependencies are jack-audio-connection-kit and
SDL2. The latter is needed for building ffplay.

Further, there are some more features with dependencies already available
in core Slackware. These are enabled by default, but can be disabled similar
to the other switches above:
CACA=yes|no (default: yes)
FONTCONFIG=yes|no (default: yes)
FREETYPE=yes|no (default: yes)
FRIBIDI=yes|no (default: yes)
GNUTLS=yes|no (default: yes)
JP2=yes|no (default: yes)
LIBCDIO=yes|no (default: yes)
LIBSSH=yes|no (default: yes)
OPENGL=yes|no (default: yes)
PULSEAUDIO=yes|no (default: yes)
SAMBA=yes|no (default: yes)
THEORA=yes|no (default: yes)
V4L2=yes|no (default: yes)
VORBIS=yes|no (default: yes)
VPX=yes|no (default: yes)
WAVPACK=yes|no (default: yes)
X11GRAB=yes|no (default: yes)