[FFmpeg-user] momentary overlay using ffmpeg

[Frank Tetzel]

Am Mon, 19 May 2014 10:37:59 +0200
schrieb Stefano Sabatini <stefasab at gmail.com>:

> On date Monday 2014-05-19 13:54:07 +0530, tarun singhal wrote:
> > On Mon, May 19, 2014 at 1:32 PM, tarun singhal
> > <tsinghal18 at gmail.com> wrote:
> > 
> > > Hi Group,
> > >
> > > When using overlay or drawtext filter, I see that it applies
> > > overlay/text over complete length of video.
> > > I have a requirement where I want to put an overlay or draw text
> > > on source video, but the overlay should appear only from lets
> > > says start time code: 00:02:00 and should remain there till
> > > 00:02:10
> > >
> > > So, basically having overlay only for 10 seconds in the source
> > > video?
> > >
> > > Is this possible to do with ffmpeg?
> [...]
> > >  I was able to figure out the command to do Draw text for
> > > momentarily-
> > Below is the sample command might come handly. Working to get
> > Overlay working like this
> > 
> > ffmpeg -i output.mpg -s 640x360 -filter_complex
> > "drawtext=fontfile=stocky.ttf:text=test:timecode='00\:00\:00\:00':r=25:fontsize=50:x=(w-tw)/2:y=h-(2*lh):fontcolor=black:enable='if(gte(t,10),lte(t,20))'"
> > -acodec copy -r 30 check.mpg
> 
> There is the timeline feature which is supposed to do exactly that:
> http://ffmpeg.org/ffmpeg-filters.html#Timeline-editing
> 
> you enable it with something like enable=between(t, 120, 130).
> 
> Check the output of ffmpeg -filters to see which filters support
> timeline.
> 
> Supporting smooth alpha transitions is not possible at the moment (at
> least not without some creative filter chaining).

There's also sendcmd:
http://ffmpeg.org/ffmpeg-filters.html#sendcmd_002c-asendcmd

Look at the second example.