Build fails on Windows 10 64bit: { command: "\"pkg-config\" \"--libs\" \"--cflags\" \"libavformat\"", cause: Os { code: 2, kind: NotFound, message: "The system cannot find the file specified." }}

[MichaelMauderer]

I'll probably work around this by using a pre-built version of ffmpeg which should avoid any issues building it.

Full output

 Compiling ffmpeg-sys v3.4.1
error: failed to run custom build command for `ffmpeg-sys v3.4.1`
process didn't exit successfully: `C:\<snip>\target\debug\build\ffmpeg-sys-a162081edadd1e97\build-script-build` (exit code: 101)
--- stderr
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Command { command: "\"pkg-config\" \"--libs\" \"--cflags\" \"libavformat\"", cause: Os { code: 2, kind: NotFound, message: "The system cannot find the file specified." } }', libcore\result.rs:945:5
stack backtrace:
   0: <std::sync::mpsc::select::Select as core::fmt::Debug>::fmt
   1: std::stdsimd::arch::detect::os::check_for
   2: std::panicking::take_hook
   3: std::panicking::take_hook
   4: std::panicking::rust_panic_with_hook
   5: std::panicking::begin_panic_fmt
   6: rust_begin_unwind
   7: core::panicking::panic_fmt
   8: core::result::unwrap_failed<pkg_config::Error>
             at C:\projects\rust\src\libcore\macros.rs:26
   9: core::result::Result<pkg_config::Library, pkg_config::Error>::unwrap<pkg_config::Library,pkg_config::Error>
             at C:\projects\rust\src\libcore\result.rs:782
  10: build_script_build::main
             at .\build.rs:518
  11: std::rt::lang_start::{{closure}}<()>
             at C:\projects\rust\src\libstd\rt.rs:74
  12: std::panicking::update_panic_count
  13: _rust_maybe_catch_panic
  14: std::rt::lang_start_internal
  15: std::rt::lang_start<()>
             at C:\projects\rust\src\libstd\rt.rs:74
  16: main
  17: invoke_main
             at f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:78
  18: __scrt_common_main_seh
             at f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:283
  19: BaseThreadInitThunk
  20: RtlUserThreadStart

[jonfk]

The error message is indicating that you don't have pkg-config installed. pkg-config is a tool that helps a build find installed libraries (here the ffmpeg libraries).

[barzamin]

Unfortunately, pkg-config isn't really a good tool to use to find libraries on Windows (cf this post and this one, which I believe are still the current state of affairs). We should perhaps fall back to building ffmpeg from source if we can't find pkg-config, targeting msvc if necessary; this is, iirc, what libcurl-sys and other core Rust *-sys crates do.

[LukasKnuth]

Any workaround to get this thing working on Win10 for now?

Also, what are the prerequirements to build this crate? Do I need to download ffmpeg libs (source or bin) before being able to compile?

[kornelski]

Your best bet to get it working on Windows is to set the build feature, and let it compile ffmpeg from scratch.