Increase video volume

$ ffmpeg -i input -vcodec copy -af "volume=20dB" output

Credit: How to increase volume in a video without re-encoding the video 

Convert .ts to .mp4

$ ffmpeg -i input.ts -acodec copy -vcodec copy out.mp4

Credit: http://stackoverflow.com/a/17916418/1032449 

Convert FLV to MP4 with FFmpeg

Only for no AV recording

$ ffmpeg -i input.flv -c copy -copyts output.mp4

Tested on: OS X 10.11
Credit: http://superuser.com/a/860127