proc av_expr_count_func(e: ptr AVExpr; counter: ptr cuint; size, arg: cint): cint {.
    importc, cdecl, ...raises: [], tags: [], forbids: [].}

proc av_expr_count_vars(e: ptr AVExpr; counter: ptr cuint; size: cint): cint {.
    importc, cdecl, ...raises: [], tags: [], forbids: [].}

proc av_expr_eval(e: ptr AVExpr; const_values: ptr cdouble; opaque: pointer): cdouble {.
    importc, cdecl, ...raises: [], tags: [], forbids: [].}

proc av_expr_free(e: ptr AVExpr) {.importc, cdecl, ...raises: [], tags: [],
                                   forbids: [].}

proc av_expr_parse(expr: ptr ptr AVExpr; s: cstring; const_names: cstringArray;
                   const_values: ptr cdouble; func1_names: cstringArray;
                   funcs1: proc (a1: pointer; a2: cdouble): cdouble;
                   func2_names: cstringArray; funcs2: proc (a1: pointer;
    a2: cdouble; a3: cdouble): cdouble; opaque: pointer; log_offset: cint;
                   log_ctx: pointer): cint {.importc, cdecl, ...raises: [],
    tags: [], forbids: [].}

proc av_expr_parse_and_eval(res: ptr cdouble; s: cstring;
                            const_names: cstringArray;
                            const_values: ptr cdouble;
                            func1_names: cstringArray;
                            funcs1: proc (a1: pointer; a2: cdouble): cdouble;
                            func2_names: cstringArray; funcs2: proc (
    a1: pointer; a2: cdouble; a3: cdouble): cdouble; opaque: pointer;
                            log_offset: cint; log_ctx: pointer): cint {.importc,
    cdecl, ...raises: [], tags: [], forbids: [].}

proc av_strtod(numstr: cstring; tail: cstringArray): cdouble {.importc, cdecl,
    ...raises: [], tags: [], forbids: [].}