Sorry email was sent before complete: https://www.ffmpeg.org/ffmpeg-utils.html#Expression-Evaluation
I regularly use this in many filters and it works just as expected, it's just that I ran into an issue with the fade filter. Thanks, Shlomo On Thu, Apr 30, 2015 at 12:31 PM, Shlomo Morosow <[email protected]> wrote: > Thanks Moritz, > The reason I need to use mathematical values is because I'd like to make a > preset command to fade out the last second of any given video and since the > fade filter needs to be instructed on when to begin in relation to the > start of the video I need to be able to tell it to start at duration minus > one second. > > Regarding the documentation on using expressions in filters, this can be > found in the the text-expansion section of the ffmpeg filters documentation: > > https://www.ffmpeg.org/ffmpeg-utils.html#Expression-Evaluation > > > To which can be applied the the expressions-evaluation found in the ffmpeg > expression-evaluation documentation: > > > > On Thu, Apr 30, 2015 at 3:50 AM, Moritz Barsnick <[email protected]> wrote: > >> On Wed, Apr 29, 2015 at 17:57:43 -0400, Shlomo Morosow wrote: >> > I need the ability to input mathematical values for setting the start >> time >> > (st) on the "fade" filter, I've attempted to use an expression and this >> > particular filter does not seem to work with expressions, nor simple >> math >> > as "10*1". >> >> As far as I can tell, you are right in saying that this filter (or at >> least the "st" argument) does not support expressions. >> >> For "st", it also doesn't make much sense. Expressions are used not for >> convenient calculation, but rather for expressing something which >> changes over the course of a media stream, i.e. depending on frame >> count, timestamp or the likes. "st" can only ever express a constant >> value. >> >> If you need to do math, you can let your interpreter (on Unix: the >> shell) do the math for you. I'm not sure how to do this on Windows (and >> usually avoid it, even professionally). ;-) >> >> > ffmpeg.exe -y -ss "0:00:20" -t "0:00:10" -i input.avi -filter_complex >> > "fade=out:st=%{expr\\\: (10-1)}:d=1" -f dvd -target ntsc-dvd -r 29.97 >> > -aspect 4:3 -b:v 4500k -mbd rd -trellis 1 -flags +mv0 -cmp 0 -subcmp 2 >> -b:a >> > 128k output.vob >> >> Where is it documented that an expression is expressed as such? >> >> Moritz >> _______________________________________________ >> ffmpeg-user mailing list >> [email protected] >> http://ffmpeg.org/mailman/listinfo/ffmpeg-user >> > > > > -- > > *Shlomo Morosow* > > *The Living Archive · Archive Manager* > > 781 East New York Ave, Brooklyn, NY 11203 > *t *718.774.1800 x1450 *c *347.693.7196 > -- *Shlomo Morosow* *The Living Archive · Archive Manager* 781 East New York Ave, Brooklyn, NY 11203 *t *718.774.1800 x1450 *c *347.693.7196 _______________________________________________ ffmpeg-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/ffmpeg-user
