[FFmpeg-user] momentary overlay using ffmpeg

[Stefano Sabatini]

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).