Support for Libyuv

[riza]

Support for libyuv library which provides YUV scaling and conversion functionality (​https://chromium.googlesource.com/libyuv/libyuv/).

Requirement

• Libyuv library. For building the library, we recommend using the steps described ​here, except for Android target as explained below.

This implementation will provide video scaling and conversion functionality.

Below are the steps to use the codec:

For GNU targets

1. Build Libyuv library. Make sure to execute the Release build step (ninja -j7 -C out/Release). The library will be built on ([libyuv_dir]/out/Release).
2. Run PJSIP's configure and specify the Libyuv folder using --with-libyuv option. E.g:

   ./configure --with-libyuv=/home/user/src/libyuv
   

For iOS targets

1. Build Libyuv library. Make sure to execute the Release build step (ninja -j7 -C out_ios/Release-iphoneos libyuv_unittest). The library will be built on ([libyuv_dir]/out_ios/Release-iphoneos).
2. Run PJSIP's configure-iphone and specify the Libyuv folder using --with-libyuv option. E.g:

   ./configure-iphone --with-libyuv=/home/user/src/libyuv
   

3. Add libyuv.a to application project in XCode. For armv7 architecture, also add libyuv_neon.a to the application project.

Notes for iOS targets:

• To build for armv7s, just follow the instructions for arm64, which will build libyuv for three architectures: armv7, armv7s, and arm64. armv7s it is still not supported because of the limitation from chromium build tools (documented in libyuv's issue ​here).

For Android targets

1. Get libyuv from ​here (tried to build using the official source, but failed).
2. From the libyuv-android directory, run ndk-build. The library will be built on ([libyuv_dir]/libs/armeabi).
3. Create dir out/Release under [libyuv_dir]/jni and copy the libyuv.so there. E.g:

   cd [libyuv_dir]
   mkdir -p jni/out/Release
   cp libs/armeabi/libyuv.so jni/out/Release
   

4. Run PJSIP's configure and specify the Libyuv folder using --with-libyuv option. E.g:

   ./configure --with-libyuv=[libyuv_dir]/jni
   

For Visual Studio

1. Build the Libyuv library.
2. Add Libyuv include and library location paths to Visual Studio search path settings.
3. Add this to your config_site.h:

   #define PJMEDIA_HAS_LIBYUV		1
   

[riza]

In 4875:

Re #1776: Initial implementation of Libyuv wrapper. Supports:

• library detection via autoconf
• scaling and conversion function (from/to I420 or BGRA)