mplayer: allow enabling v4l2 driver for e.g webcams

- add flag for enabling v4l2 support for the tv backend
- required for some webcams
- off by default as no other package seems to be relying on it so far

pkgs/applications/video/mplayer/default.nix

@@ -21,6 +21,7 @@
 , jackaudioSupport ? false, libjack2 ? null
 , pulseSupport ? config.pulseaudio or false, libpulseaudio ? null
 , bs2bSupport ? false, libbs2b ? null
+, v4lSupport ? false, libv4l ? null
 # For screenshots
 , libpngSupport ? true, libpng ? null
 , libjpegSupport ? true, libjpeg ? null
@@ -53,6 +54,7 @@ assert pulseSupport -> libpulseaudio != null;
 assert bs2bSupport -> libbs2b != null;
 assert libpngSupport -> libpng != null;
 assert libjpegSupport -> libjpeg != null;
+assert v4lSupport -> libv4l != null;
 
 let
 
@@ -132,6 +134,7 @@ stdenv.mkDerivation rec {
     ++ optional libpngSupport libpng
     ++ optional libjpegSupport libjpeg
     ++ optional bs2bSupport libbs2b
+    ++ optional v4lSupport libv4l
     ++ (with darwin.apple_sdk.frameworks; optionals stdenv.isDarwin [ Cocoa OpenGL ])
     ;
 
@@ -156,6 +159,7 @@ stdenv.mkDerivation rec {
     (if x264Support then "--enable-x264 --disable-x264-lavc" else "--disable-x264 --enable-x264-lavc")
     (if jackaudioSupport then "" else "--disable-jack")
     (if pulseSupport then "--enable-pulse" else "--disable-pulse")
+    (if v4lSupport then "--enable-v4l2 --enable-tv-v4l2" else "--disable-v4l2 --disable-tv-v4l2")
     "--disable-xanim"
     "--disable-ivtv"
     "--disable-xvid --disable-xvid-lavc"