Update dependencies, FFmpeg binding doc, README

Author: ldm0

Cargo.toml

@@ -26,17 +26,17 @@ build = "build.rs"
 doctest = false
 
 [dependencies]
-once_cell = "1.4.1"
-libc = "0.2.79"
+once_cell = "1.5"
+libc = "0.2"
 
 [build-dependencies]
-bindgen = "0.55.1"
-once_cell = "1.4.1"
+bindgen = "0.57"
+once_cell = "1.5"
 
 [target.'cfg(not(windows))'.build-dependencies]
-pkg-config = "0.3.19"
-num_cpus = "1.13.0"
+pkg-config = "0.3"
+num_cpus = "1.13"
 
 [target.'cfg(windows)'.build-dependencies]
-vcpkg = "0.2.10"
+vcpkg = "0.2"
 

README.md

@@ -13,18 +13,26 @@ Cross platform FFI bindings for FFmpeg inner libraries. This is a crate that:
 
 To use this crate, you need to set several environment variables.
 
-### To link: 
+### Simplest:
+
+Build ffmpeg staticly and set `FFMPEG_PKG_CONFIG_PATH` to the path of the generated FFmpeg package-config files. And you don't need to set other environment variables for static linking.
+
+### More complex
+
+You need to set environment variable for both linking and generating bindings.
+
+#### To link: 
 
 1. Dynamic linking with prebuilt dylib: Set `FFMPEG_DLL_PATH` to the path of `dll` or `so`. (Windows: Put corresponding `.lib` file next to the `.dll` file.)
 
-2. Static linking with prebuilt staticlib: Set `FFMPEG_PKG_CONFIG_PATH` to the path of the FFmpeg package-config files or set `FFMPEG_LIB_DIR` to the path of the FFmpeg prebuilt libs directory.
+2. Static linking with prebuilt staticlib:  or set `FFMPEG_LIB_DIR` to the path of the FFmpeg prebuilt libs directory.
 
-### To generate bindings: 
+#### To generate bindings: 
 
 1. Compile-time binding generation(requires clang dylib): Set `FFMPEG_INCLUDE_DIR` to the path to the header files for binding generation.
 
 2. Use pre-built binding: Set `FFMPEG_BINDING_PATH` to the prebuilt binding file.
 
-### Attention
+## Attention
 
 FFI is not that easy, especially when you are dealing with a big old C project. Don't feel depressed when there are some problems. The CI check already have some typical use cases, you can check it. File an issue if you still have some problem.