[FFmpeg-user] Docs, filtering introduction example

littlebat dashing.meng at gmail.com
Fri Apr 5 11:00:21 CEST 2013

On Fri, 5 Apr 2013 10:45:37 +0200
Michael Ludwig <milu71 at gmx.de> wrote:

> Carl Eugen Hoyos schrieb am 04.04.2013 um 20:30 (+0000):
> > Michael Ludwig <milu71 <at> gmx.de> writes:
> > > (Okay, no error with N-51511-g599866f from 2013-04-01, 
> > > but not the desired result either.)
> > 
> > This is ticket #2413, a patch is currently discussed 
> > on ffmpeg-devel.
> > Further improvements are of course welcome!
> Okay, I agree with the #2413 author.
> Will see if I can improve the docs.
> By the way, the reason the original example on the doc page
> is wrong is because (a) it crops the bottom half of the
> image which isn't supposed to appear in the output at all,
> and (b) it uses the cropped part as the main input for the
> overlay, so the resulting output ends up too small.
> The #2413 author posted a correct example, at the end of
> the ticket description, where he uses a fifo filter, which
> could be removed, I think (although I don't understand its
> purpose), and which has been removed recently.
> http://ffmpeg.org/trac/ffmpeg/ticket/2413
> [FFmpeg-devel] [PATCH] doc: remove mention of fifo filter in the
> introduction.
> http://ffmpeg.org/pipermail/ffmpeg-devel/2012-December/135982.html
> I think the following examples are clear, in decreasing
> order of explicitness:
> -vf "[in] split [S1][S2]; [S2] crop=iw:ih/2:0:0, vflip [Mir]; [S1]
> [Mir] overlay=0:H/2 [out]" -vf "[in] split [Whole], crop=iw:ih/2:0:0,
> vflip [Mir]; [Whole][Mir] overlay=0:H/2 [out]" -vf "[in] split
> [Whole], crop=iw:ih/2:0:0, vflip, [Whole] overlay=0:H/2 [out]"

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