gnu: ffmpeg: Update to 4.0.

* gnu/packages/video.scm (ffmpeg): Update to 4.0.
* gnu/packages/video.scm (ffmpeg@3.4): New variable.
* gnu/packages/video.scm (ffmpeg-git): Remove variable.
* gnu/packages/video.scm (mpv)[inputs]: Build with ffmpeg instead of ffmpeg-git.
* gnu/packages/gstreamer.scm (gst-libav)[inputs]: Build with ffmpeg@3.4 instead
of ffmpeg.
* gnu/packages/messaging.scm (qtox)[inputs]: Build with ffmpeg@3.4 instead of
ffmpeg.
* gnu/packages/emulators.scm (dolphin-emu)[inputs]: Build with ffmpeg@3.4
instead of ffmpeg.
* gnu/packages/gnunet.scm (libextractor)[inputs]: Build with ffmpeg@3.4 instead
of ffmpeg.

gnu/packages/emulators.scm

@@ -186,7 +186,7 @@
          ("bluez" ,bluez)
          ("curl" ,curl)
          ("eudev" ,eudev)
-         ("ffmpeg" ,ffmpeg)
+         ("ffmpeg" ,ffmpeg-3.4)
          ("font-wqy-microhei" ,font-wqy-microhei)
          ("freetype" ,freetype)
          ("glew" ,glew)

gnu/packages/gnunet.scm

@@ -88,7 +88,7 @@
     `(("exiv2" ,exiv2)
       ("bzip2" ,bzip2)
       ("flac" ,flac)
-      ("ffmpeg" ,ffmpeg)
+      ("ffmpeg" ,ffmpeg-3.4)
       ("file" ,file)                           ;libmagic, for the MIME plug-in
       ("glib" ,glib)
       ("gstreamer" ,gstreamer)

gnu/packages/gstreamer.scm

@@ -403,7 +403,7 @@ distribution problems in some jurisdictions, e.g. due to patent threats.")
        ("python" ,python)))
     (inputs
      `(("gst-plugins-base" ,gst-plugins-base)
-       ("ffmpeg" ,ffmpeg)
+       ("ffmpeg" ,ffmpeg-3.4)
        ("orc" ,orc)
        ("zlib" ,zlib)))
     (home-page "https://gstreamer.freedesktop.org/")

gnu/packages/messaging.scm

@@ -913,7 +913,7 @@ instant messenger with audio and video chat capabilities.")
                    ,(list (string-append (assoc-ref inputs "qtsvg")
                                          "/lib/qt5/plugins/"))))))))))
     (inputs
-     `(("ffmpeg" ,ffmpeg)
+     `(("ffmpeg" ,ffmpeg-3.4)
        ("filteraudio" ,filteraudio)
        ("glib" ,glib)
        ("gtk+" ,gtk+-2)

gnu/packages/video.scm

@@ -597,14 +597,14 @@ standards (MPEG-2, MPEG-4 ASP/H.263, MPEG-4 AVC/H.264, and VC-1/VMW3).")
 (define-public ffmpeg
   (package
     (name "ffmpeg")
-    (version "3.4.2")
+    (version "4.0")
     (source (origin
              (method url-fetch)
              (uri (string-append "https://ffmpeg.org/releases/ffmpeg-"
                                  version ".tar.xz"))
              (sha256
               (base32
-               "0h6prjn1ijkzzhkyj8mazp0wpx7m0n9ycadjxagf9czqirbyk4ib"))))
+               "0gx4ngnhi5glmxh38603qy5n6vq8bl1cr4sqd1xff95i82pmv57d"))))
     (build-system gnu-build-system)
     (inputs
      `(("fontconfig" ,fontconfig)
@@ -770,6 +770,18 @@ convert and stream audio and video.  It includes the libavcodec
 audio/video codec library.")
     (license license:gpl2+)))
 
+(define-public ffmpeg-3.4
+  (package
+    (inherit ffmpeg)
+    (version "3.4.2")
+    (source (origin
+             (method url-fetch)
+             (uri (string-append "https://ffmpeg.org/releases/ffmpeg-"
+                                 version ".tar.xz"))
+             (sha256
+              (base32
+               "0h6prjn1ijkzzhkyj8mazp0wpx7m0n9ycadjxagf9czqirbyk4ib"))))))
+
 (define-public ffmpeg-2.8
   (package
     (inherit ffmpeg)
@@ -790,25 +802,6 @@ audio/video codec library.")
                     flag))
               ,flags))))))
 
-;; Annoyingly enough, the latest mpv release does not build with the stable
-;; release of ffmpeg. Use a git commit until the situation is fixed.
-(define-public ffmpeg-git
-  (let ((commit "3f887440677328c9cfed97ad81d14051ffa32aae")
-        (revision "1"))
-    (package
-     (inherit ffmpeg)
-     (name "ffmpeg-git")
-     (version (string-append "3.4-" revision "." (string-take commit 9)))
-     (source (origin
-              (method git-fetch)
-              (uri (git-reference
-                    (url "https://github.com/FFmpeg/FFmpeg.git")
-                    (commit commit)))
-              (file-name (string-append name "-" version "-checkout"))
-              (sha256
-               (base32
-                "1b7n3g4m2rbvrwsgbfl8wl91z42g1ld42clwxs8qpl9ny5rwz6sq")))))))
-
 (define-public vlc
   (package
     (name "vlc")
@@ -1032,7 +1025,7 @@ SVCD, DVD, 3ivx, DivX 3/4/5, WMV and H.264 movies.")
     (inputs
      `(("alsa-lib" ,alsa-lib)
        ("enca" ,enca)
-       ("ffmpeg" ,ffmpeg-git)
+       ("ffmpeg" ,ffmpeg)
        ("jack" ,jack-1)
        ("ladspa" ,ladspa)
        ("lcms" ,lcms)