ffmpeg enable libvpx (WebM encoder) (#545)

* ffmpeg enable libvpx (WebM encoder)

https://trac.ffmpeg.org/wiki/Encode/VP8

* enable vp8 in libvpx and edit comments about libvpx in ffmpeg

packages/ffmpeg/build.sh

@@ -5,7 +5,9 @@ TERMUX_PKG_SRCURL=https://www.ffmpeg.org/releases/ffmpeg-${TERMUX_PKG_VERSION}.t
 TERMUX_PKG_SHA256=49cc3105f7891c5637f8fabb1b75ebb19c9b5123b311a3ccc6182aa35d58b89a
 TERMUX_PKG_FOLDERNAME=ffmpeg-$TERMUX_PKG_VERSION
 # libbz2 is used by matroska decoder:
-TERMUX_PKG_DEPENDS="openssl, libbz2, libx264, xvidcore, libvorbis, libmp3lame, libopus"
+# libvpx is the VP8 & VP9 video encoder for ​WebM, an open, royalty-free media file format.
+# see https://trac.ffmpeg.org/wiki/Encode/VP8 and https://trac.ffmpeg.org/wiki/Encode/VP9
+TERMUX_PKG_DEPENDS="openssl, libbz2, libx264, xvidcore, libvorbis, libmp3lame, libopus, libvpx"
 TERMUX_PKG_INCLUDE_IN_DEVPACKAGE="share/ffmpeg/examples"
 TERMUX_PKG_CONFLICTS="libav"
 
@@ -49,6 +51,7 @@ termux_step_configure () {
 		--enable-libopus \
 		--enable-libx264 \
 		--enable-libxvid \
+		--enable-libvpx \
 		--enable-nonfree \
 		--enable-openssl \
 		--enable-shared \

packages/libvpx/build.sh

@@ -1,5 +1,5 @@
 TERMUX_PKG_HOMEPAGE=http://www.webmproject.org/
-TERMUX_PKG_DESCRIPTION="VP9 Codec SDK"
+TERMUX_PKG_DESCRIPTION="VP8 & VP9 Codec SDK"
 TERMUX_PKG_VERSION=1.6.0
 TERMUX_PKG_SRCURL=https://github.com/webmproject/libvpx/archive/v${TERMUX_PKG_VERSION}.tar.gz
 TERMUX_PKG_FOLDERNAME=libvpx-${TERMUX_PKG_VERSION}
@@ -26,7 +26,7 @@ termux_step_configure () {
 		$_CONFIGURE_TARGET \
 		--prefix=$TERMUX_PREFIX \
 		--disable-examples \
-		--disable-vp8 \
+		--enable-vp8 \
 		--enable-shared \
 		--enable-small
 }