1. The following packages are required by the build scripts.

autoconf automake libtool pkg-config curl git

2. These optional packages should be installed only if you want to build corresponding external libraries.

cmake gcc gperf texinfo yasm nasm bison autogen patch

• cmake v3.9.x or later required by libwebp and x265
• gcc required by freetype and fribidi
• gperf required by fontconfig
• texinfo required by gmp on some platforms
• yasm required for libvpx and x265 on some platforms
• nasm required for x264 on x86 and x86-64 platforms
• bison required for gnutls
• autogen required for libsndfile
• patch required for x265

3. iOS builds require these extra packages and tools.

• Xcode 7.3.1 or later
• iOS SDK 9.3 or later
• Command Line Tools from Downloads for Apple Developers