18 May
2011
18 May
'11
1:11 p.m.
L'octidi 28 floréal, an CCXIX, littlebat a écrit :
I can't understand how to use "-vol" parameter to increase volume in ffmpeg. I know "-vol 256" mean keep volume unchanged. But I don't know how to choose a proper number for a video file to increase volume. For example, does "-vol 512" mean volume intensity is twice as original file?
Just try it for yourself: perl -e 'print pack("s*", 3000, 2000, 1000, 0, -1000, -2000)' | ffmpeg -f s16le -i - -vol 512 -f s16le - 2> /dev/null | perl -e '$/=\2; while(<>) { print unpack("s", $_), "\n" }' Of course, you can do exactly the same with any GUI PCM editor. By looking at the result, you can see that obviously each sample is multiplied by vol/256. Regards, -- Nicolas George