increase volume (louder) with ffmpeg

The <audio_volume> is a number. 256 is normal. I think if you use 512 then it will double the volume. I got the information from here:-http://lists.mplayerhq.hu/pipermail/...ry/013869.html

ffmpeg -i <input_file> -vol <audio_volume> -acodec <audio_codec> <other_parameters> <output_file>