Adding support for android (and others architectures)

[lattice0]

Hi, I'll add support for other architectures. Take a look at the structure of the prebuilt binaries I have:

|-- android
|   |-- arm64-v8a
|   |   |-- include
|   |   |-- lib
|   |   `-- share
|   |-- armeabi-v7a
|   |   |-- include
|   |   |-- lib
|   |   `-- share
|   |-- x86
|   |   |-- include
|   |   |-- lib
|   |   `-- share
|   `-- x86_64
|       |-- include
|       |-- lib
|       `-- share
`-- desktop
    |-- aarch64
    |   |-- include
    |   |-- lib
    |   `-- share
    |-- x86_64
    |   |-- bin
    |   |-- include
    |   |-- lib
    |   `-- share
    `-- x86_64_generic
        |-- bin
        |-- include
        |-- lib
        `-- share

they're respecting android's jniLibs search model (even though we won't use it in this project). I have a docker container that builds then in this structure. For desktop this container builds with some hardware decoding support which is nice, I may link it here in the future, gotta clean it.

Anyways, looks like for now, rust-ffmpeg-sys supports specifying a folder that contains lib, bin, include. I'm planning to add an environment variable called MULTI_ARCHITECTURE_PREBUILT which would point to the root of my tree I just pasted here. Then if it's android it goes into android + right arch. I think I might change desktop/{x86_64,aarch64,x86_64_generic} to desktop/{linux/macos/windows}/{x86_64,aarch64,x86_64_generic}. Also there should be an iOS folder. What you think?

I'll have to delay iOS, Windows and macOS support because I dont have them now to build, but I plan to support them.

I also didn't look at how to use cargo to cross compile (for android for now) using build.rs. Gonna look on that. If somebody have a tip I appreciate. I want to build for android on linux, and for linux on linux (which already works)

[lattice0]

Here's a draft:

https://github.com/meh/rust-ffmpeg-sys/compare/master...lucaszanella:master

It's working when build to linux on linux. When building to android on linux using https://mozilla.github.io/firefox-browser-architecture/experiments/2017-09-21-rust-on-android.html (make standalone toolchain script), it starts selecting the dependencies and include paths correctly but it currently fails with this:

/usr/include/x86_64-linux-gnu/gnu/stubs.h:7:11: fatal error: 'gnu/stubs-32.h' file not found
  /usr/include/x86_64-linux-gnu/gnu/stubs.h:7:11: fatal error: 'gnu/stubs-32.h' file not found, err: true
  thread 'main' panicked at 'Unable to generate bindings: ()', build.rs:1249:6

probably something related with bindings library, gonna investigate.

[lattice0]

Installing libc6-dev-i386 fixed the last error.

I removed avdevice since I dont have this lib for android. Using:

cargo build --verbose -vv --target aarch64-linux-android --release --no-default-features --features "avcodec avfilter avformat swresample swscale"

made the building work!

Gonna take a while to test on Android with real video data but it seems everything is ok :+1:

I think I'm gonna wait a little to send a PR though? Don't know, gonna test more. I plan to add support for raspberry pi and nvidia jetson nano because I'm gonna use them in my project in the future, but cross compiling for them is kinda hard I guess.

[kornelski]

Thanks for this work. It's fine if you send a PR early. Others can help testing too.