Right now the new Screen recorder that MIUI developed is only available on the Beta roms, but it can be some what easily installed on the Global Rom.
- Download the app from APK mirror
- Download the attached file which contains the libraries needed by the app to work
- Copy the two files named "libMiuiScreenRecord.so" on /system/lib and /system/lib64 respectively. They have the same name, but are different files, so don't get confused.
- Assign permissions rw-r--r-- 644 to the copied files (or use MiXplorer Beta to copy the files)
- Install the APK downloaded from APK mirror.
- That's all.
- The app can't record internal sound (at least on my device. Needs more testing). Aside from that, it can record from the mic.
- The process of copying the libs was made with the app MiXplorer Beta, so I didn't have to worry about assigning permissions to the files (apparently the app assigns the permissions automatically).
- You obviously need root.