Error using plot

julia> using Plots
[ Info: Precompiling Plots [91a5bcdd-55d7-5caf-9e0b-520d859cae80]
ERROR: LoadError: UndefVarError: ffmpeg not defined
Stacktrace:
[1] top-level scope at C:\Users\Lenovo.julia\packages\FFMPEG\9JQpZ\src\FFMPEG.jl:55
[2] include at .\boot.jl:328 [inlined]
[3] include_relative(::Module, ::String) at .\loading.jl:1094
[4] include(::Module, ::String) at .\Base.jl:31
[5] top-level scope at none:2
[6] eval at .\boot.jl:330 [inlined]
[7] eval(::Expr) at .\client.jl:432
[8] top-level scope at .\none:3
in expression starting at C:\Users\Lenovo.julia\packages\FFMPEG\9JQpZ\src\FFMPEG.jl:55
ERROR: LoadError: Failed to precompile FFMPEG [c87230d0-a227-11e9-1b43-d7ebe4e7570a] to C:\Users\Lenovo.julia\compiled\v1.2\FFMPEG\TGvga.ji.
Stacktrace:
[1] error(::String) at .\error.jl:33
[2] compilecache(::Base.PkgId, ::String) at .\loading.jl:1253
[3] _require(::Base.PkgId) at .\loading.jl:1013
[4] require(::Base.PkgId) at .\loading.jl:911
[5] require(::Module, ::Symbol) at .\loading.jl:906
[6] include at .\boot.jl:328 [inlined]
[7] include_relative(::Module, ::String) at .\loading.jl:1094
[8] include(::Module, ::String) at .\Base.jl:31
[9] top-level scope at none:2
[10] eval at .\boot.jl:330 [inlined]
[11] eval(::Expr) at .\client.jl:432
[12] top-level scope at .\none:3
in expression starting at C:\Users\Lenovo.julia\packages\Plots\Ih71u\src\Plots.jl:11
ERROR: Failed to precompile Plots [91a5bcdd-55d7-5caf-9e0b-520d859cae80] to C:\Users\Lenovo.julia\compiled\v1.2\Plots\ld3vC.ji.
Stacktrace:
[1] error(::String) at .\error.jl:33
[2] compilecache(::Base.PkgId, ::String) at .\loading.jl:1253
[3] _require(::Base.PkgId) at .\loading.jl:1013
[4] require(::Base.PkgId) at .\loading.jl:911
[5] require(::Module, ::Symbol) at .\loading.jl:906

You may be running into

which is an issue with FFMPEG.