While I regret purchasing a Raspberry Pi 2 for use as a media centre (more on that another time), it's still more than serviceable if you want to use OpenELEC, OSMC or other home theatre distro. That is until you run up against videos encoded in H.265 / HEVC, which even the Pi 3 can struggle with.
H.264 is definitely the most popular video codec right now, but it won't be long before the majority of online media is using the more efficient HEVC. If you're planning to stick with your Raspberry Pi 2 or 3, you'll want to convert these files to H.264, which the Pi's GPU has hardware decoding support for.
Fortunately, conversion is straightforward with FFmpeg. Because the video stream has to be re-encoded, it'll take more time than a simple container switch to get the job done.
Grab the latest Windows binaries for FFmpeg and install them to a directory accessible from the PATH environment settings. Then create a batch file in the directory containing the HEVC-encoded files and paste the following code into it.
for %%i in (*.mkv) do ffmpeg -i "%%i" -c:a copy -sn -map 0:0 -map 0:1 -vcodec libx264 "output\%%i"
Note you'll need to change the
*.mkv to match the extension of the video files you're converting.
Basically, this command does the minimum work needed to transform the videos from H.265 to H.264. The audio is copied directly, so the only cost is the video re-encoding. If there are a lot of files to encode, you'll be in for a wait.
FFmpeg can take advantage of multiple cores by default, so running extra instances to speed-up the conversion will have the opposite effect. Optionally, you can reduce the resolution — say, 1080p to 720p — to improve speeds.