[FFmpeg-user] Sliding text banner (was: Newbie questions)

Nicolas George nicolas.george at normalesup.org
Mon Jul 23 10:55:55 CEST 2012

Le quintidi 5 thermidor, an CCXX, Orbisoft Support a écrit :
> 1) If I want to simply make a video out of the ticker only, would I still
> need an original video to overlay the text on or can I simply create it from
> the drawtext? If I do need a blank video to start with (e.g. a black
> rectangle 1920x50 pixels) how would I know how long to create the video for
> and how could I create it?

You can use the "color" filter source:

The correct duration depends on the total width of your text. drawtext
prints it at debug level, so you can get it using -loglevel debug.

> 2) The drawstring text in http://www.orbisoft.com/ffmpeg/test001.flv doesn't
> in my opinion appear as smooth as the png animation - was a bit jumpy
> occasionally. I know my png were anti-aliased.

I am not sure what you mean. "Jumpy" is about movement, while "anti-aliased"
is about the quality of each images individually.

If you mean the artifacts around the edges of the letters, this is
completely normal: FLV1 is a lossy video codec. Video codecs are especially
bad at sharp edges, and a text on black background is all about sharp edges.
Furthermore, you did not add any option to increase the bit rate (bigger
file, less artifacts), keeping the somewhat low default.

>						 Do you know how I could
> improve it?

Do not use intermediary files.

I repeat: do not use intermediary files.

ffmpeg have everything you need to produce the final output in a single run,
either from your PNGs (if you could use ffmpeg to produce the intermediary
video from them, you can use them directly in your final run: they are,
together, a video) or using builtin features (drawtext to display the text,
drawbox to put the black background behind).

Every temporary file you use is likely to cause quality loss, especially if
you do not choose your formats, codecs and settings carefully.


  Nicolas George
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