Improve messages printed when there is no input/output file, making them more grammatically correct and consistent with other equivalent messages.
Improve messages printed when there is no input/output file, making
them more grammatically correct and consistent with other equivalent
messages.


git-svn-id: a4d7c1866f8397a4106e0b57fc4fbf792bbdaaaf@15869 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg