Update readme

Author: ldm0

README.md

@@ -4,24 +4,21 @@
 [![Crates.io](https://img.shields.io/crates/v/rusty_ffmpeg.svg)](https://crates.io/crates/rusty_ffmpeg)
 [![Doc](https://docs.rs/rusty_ffmpeg/badge.svg)](https://docs.rs/rusty_ffmpeg)
 
-FFI bindings for FFmpeg inner libraries. This is a crate that:
+Cross platform FFI bindings for FFmpeg inner libraries. This is a crate that:
 1. Generates Rust binding for FFmpeg libraries which can be used directly.
 2. Emits specific cargo metadata for linking FFmpeg libraries.
 
 ## Building
 
-### Prerequisites  
-
-1. Linux environment.
-2. Rust environment([Install](https://www.rust-lang.org/tools/install)).
-
 ### Generate and build the bindings:  
 
-Run `cargo build` to build the bindings:
+Library linking is static by default, setting environment variable `FFMPEG_DYNAMIC_LINKING` will make rusty_ffmpeg link dynamic libraries.
+
+#### Linux & MacOS
 
 1. Start to prepare FFmpeg libraries:
-    + If you have a pre-built ffmpeg, set `PKG_CONFIG_PATH` to the path which points to `*.pc` files in the build result(e.g. `PKG_CONFIG_PATH="$HOME/ffmpeg_build/lib/pkgconfig" cargo build`) then this crate will use the pre-built FFmpeg libraries.  
-    + If no `PKG_CONFIG_PATH` is set, this crate will first check if there are `libav*-dev` installed in this system.
+    + If you have a pre-built ffmpeg, set `FFMPEG_PKG_CONFIG_PATH` to the path which points to `*.pc` files in the build result(e.g. `FFMPEG_PKG_CONFIG_PATH="$HOME/ffmpeg_build/lib/pkgconfig" cargo build`) then this crate will use the pre-built FFmpeg libraries.  
+    + If no `FFMPEG_PKG_CONFIG_PATH` is set, this crate will first check if there are `libav*-dev` installed in this system.
         + If the libraries exists, this crate will use them.
         + If not, it will git clone the FFmpeg from <https://github.com/ffmpeg/ffmpeg> and then configure and compile it for you.
 2. After the FFmpeg libraries are ready, the build script will take advantage of the package-config(`*.pc`) files to:  
@@ -30,12 +27,16 @@ Run `cargo build` to build the bindings:
 
 So there are three ways for developers to provide FFmpeg libraries for this crate to generate bindings:  
 
-1. Provide self compiled FFmpeg by setting `PKG_CONFIG_PATH`
+1. Provide self compiled FFmpeg by setting `FFMPEG_PKG_CONFIG_PATH`
 2. Install FFmpeg libraries via system package manager.(Make sure they can be found by pkg-config)
 3. Doesn't provide FFmpeg, waiting for this crate cloning and building a FFmpeg with some default configuration from scratch.
 
-## Testing
+### Windows
+
+1. Install vcpkg.
+2. Install FFmpeg using it with specific triplet according to your building target and rustflags. (Check [here](https://github.com/ldm0/rusty_ffmpeg/blob/bf4ee3c5c826443426d3f5c1ac6417b43fc88429/.github/workflows/ci.yml#L325)).
+3. build with `VCPKG_ROOT` set to the vcpkg path, and `VCPKG_DEFAULT_TRIPLET` set to the triplet you used.
 
-You can use `cargo test` to test the generated bindings. If you haven't run `cargo build` and you have pre-built FFmpeg libraries. Set the `PKG_CONFIG_PATH` like this: `PKG_CONFIG_PATH="$HOME/ffmpeg_build/lib/pkgconfig" cargo test` which doesn't need to build the FFmpeg separately.
+## Testing
 
-To see it works, you can run `cargo run --example slice`.
+You can use `cargo test` to test the generated bindings. Want to see it works? There is a small example for you. Run `cargo run --example slice`.