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

[Orbisoft Support]

Thanks. I switched from FLV to MP4 and noticed the final output file went
from 145 MB down to just 11 MB which was good.

*"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."
*

Even though the RSS text file content (and therefore text length) is not
static -- i.e. it changes each time we read it (my ASP.NET code had used
the code below to measure the text length in pixels)?

' see how big the text will be
intClsTextRectangleWidth = CInt(DrawGraphics.MeasureString(strTheText,
DrawFont).Width)
intClsTextRectangleHeight = CInt(DrawGraphics.MeasureString(strTheText,
DrawFont).Height)


On Mon, Jul 23, 2012 at 8:55 PM, Nicolas George <
nicolas.george at normalesup.org> wrote:

> 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:
> http://ffmpeg.org/ffmpeg.html#color
>
> 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.flvdoesn'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.
>
> Regards,
>
> --
>   Nicolas George
>
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