Hi All, With your help, I can build ffmpeg successfully on WinRT ARM, and I create a path to make ffmpeg support WinRT-API. I have redirect some unsupported apis to WinRT supported apis. I hope you can merge to master. Also, there is a bug in float_dsp_init_vfp.c, about av_restrict -void ff_butterflies_float_vfp(float *restrict v1, float *restrict v2, int len);+void ff_butterflies_float_vfp(float *av_restrict v1, float *av_restrict v2, int len); Hope you can use them. Best regards,Jesse