Constant rsmpeg::ffi::AVPixelFormat_AV_PIX_FMT_BGR4

pub const AVPixelFormat_AV_PIX_FMT_BGR4: i32 = 18;

< packed RGB 1:2:1 bitstream, 4bpp, (msb)1B 2G 1R(lsb), a byte contains two pixels, the first pixel in the byte is the one composed by the 4 msb bits