Andrew gave some good advice too. Although I disagree with his view that he isn't an expert.
You should change one thing: don't use -q:v with libx264. Use -crf instead. See the crf section in the FFmpeg and x264 Encoding Guide. It has examples and explanations.
You may encounter two problems with your command, depending on your input. If -1 from your scale filter ends up being an odd value libx264 may complain, "height not divisible by 2". This can be an alternative method:
IIRC, if height ends up being an odd value it will automatically round down to an even value. You can do the same for width too:
The other potential issue is that flv container probably only accepts certain MP3 audio sample rates. ffmpeg, by default, will usually inherit the input sample rate for the output. If you end up with 48000 for example, then ffmpeg will complain:
FLV does not support sample rate 48000, choose from (44100, 22050, 11025)