Support v4l2

[tpoisonooo]

Hi, I'd like to open ubuntu camera with v4l2 and add new API in src/format/mod.rs:

pub fn input_v4l2<P: AsRef<Path>>(path: &P) -> Result<context::Input, Error> {
    unsafe {
        let mut ps = ptr::null_mut();
        let path = from_path(path);

        let format = CString::new("v4l2").unwrap();
        let x = av_find_input_format(format.as_ptr());

        match avformat_open_input(&mut ps, path.as_ptr(), x, ptr::null_mut()) {
            0 => match avformat_find_stream_info(ps, ptr::null_mut()) {
                r if r >= 0 => Ok(context::Input::wrap(ps)),
                e => {
                    avformat_close_input(&mut ps);
                    Err(Error::from(e))
                }
            },

            e => Err(Error::from(e)),
        }
    }
}

I have tried

• use let format = CString::new("video4linux2").unwrap();
• add enable!(configure, "BUILD_LIB_V4L2", "libv4l2"); in rust-ffmpeg-sys/build.rs

but x is still nullptr

155	        let x = av_find_input_format(format.as_ptr());
(gdb) n
157	        match avformat_open_input(&mut ps, path.as_ptr(), x, ptr::null_mut()) {
(gdb) p x
$1 = (ffmpeg_sys_next::AVInputFormat *) 0x0

Would you please give me an example to open linux camera which dev is "/dev/video0" ?

[tpoisonooo]

linux v4l2 feature has been implement on this repo : https://github.com/tpoisonooo/rust-ffmpeg-sys

To compile with the feature, some dep must be installed:

$ sudo apt install libv4l-dev lzma-dev