Develop code to FFmpeg

Hello, I want to improve this code : class VideoConverter def convertir_video(video_hash) system("ffmpeg -y -i public/videos/#{video_hash}.flv -vcodec libx264 -vpre slow -vpre medium -r 25 -s 320x240 -async 1 -ac 2 -ab 96000 public/videos/#{video_hash}.mp4 && MP4Box -inter 500 public/videos/#{video_hash}.mp4") end handle_asynchronously :convertir_video def convertir_video_3gp(video_hash) system("ffmpeg -i public/videos/#{video_hash}.3gp -sameq public/videos/#{video_hash}.mp4") end handle_asynchronously :convertir_video_3gp def revisar_video_mp4(video_hash) system("ffmpeg -y -i public/videos/#{video_hash}.mp4 -vcodec libx264 -vpre slow -vpre medium -r 25 -s 320x240 -async 1 -ac 2 -ab 96000 public/videos/#{video_hash}.mp4 && MP4Box -inter 500 public/videos/#{video_hash}.mp4") end handle_asynchronously :revisar_video_mp4 We have : 1. Ubuntu Server DigitalOcean 2. The code is a part of an app built in ruby on rails 3. The code need convert the video for reproduce to web and app mobile.