About cross compile of OpenCV with ffmpeg in emscripten

As regular problem of opencv ,I cross compiled opencv with ffmpeg in emscripten.
As today I have nothing to do.
My pc is ubuntu 16.04

Get opencv 3.2.0 from github
Only this version success .other version become runtime error.
Upper version become soft float errror.
Lower version cannot cross compile

2.Get ffmpeg from github (latest version)
3.Comple ffmpeg
emconfigure ./configure --cc=emcc --ar=emar --ranlib=emranlib --prefix=$(pwd)/…/dist --enable-cross-compile --target-os=none --arch=x86_32 --cpu=generic --disable-stripping --disable-programs --disable-asm --disable-doc --disable-pthreads --disable-w32threads --disable-debug --enable-decoder=hevc --enable-parser=hevc --enable-demuxer=hevc --enable-decoder=h264 --enable-parser=h264 --enable-demuxer=h264

make install
(I find this from google)

4.Comple opencv without ffmpeg and test with your code.(vodeo player sample?)
" emcmake cmake … -DCMAKE_INSTALL_PREFIX="“hogehoge”
And next I tuned this with cmake-gui.
make install
And set this in ofxOpencv
And compile with your code.

5.Comple opencv with ffmpeg and test with your code.
if your ffmpeg output *.a file is in AAA folder.

$ cd “your opencv make dir”
$ cmake-gui .
and configure-generate
and cheke output

if you succeeded ffmpeg will be ON
you will see like this output
" Video I/O:
avcodec: YES (ver 58.33.100)
avformat: YES (ver 58.19.100)
avutil: YES (ver 56.19.101)
swscale: YES (ver 5.2.100)
avresample: NO

make install
if you get some errors check with cmake-gui or search in google.

I tested this with my code .
I think it is no matter.

Today I checked performance .
But not change .(a llitle changed)
What’s wrong with this?