[FFmpeg-user] Taking screenshots before and after re-encoding

Carl Eugen Hoyos cehoyos at ag.or.at
Sat Feb 13 20:11:37 CET 2016

Martin Cracauer <cracauer <at> cons.org> writes:

> Out of curiosity, is there ever a need for a second 
> filter_complex?

I don't understand:
I don't know if there is a need but only one filter_complex 
can be supplied.

> Is there anything that ffmpeg can do that you cannot 
> put into a filter_complex 

(I suspect this is not the answer you were looking for, I 
fear I don't understand the question though.)

> so that you then have to have a second one after the
> non-filter-complex statement?

I still don't understand;-(

Let me add the following to my answer to your first email:
FFmpeg allows you to specify an input (often a file). 
This input will be decoded by FFmpeg (to a raw video 
format in case of video), the decoded data can be fed 
into a filter chain, the output of the filter chain 
is then sent to an encoder that outputs a different format 
(that you cannot feed into a filter chain because it is 
not the required raw format) which is accepted by a 
FFmpeg does not allow to send your encoded data to a 
decoder to allow a second filter chain: You need two 
instances of FFmpeg to do that.
(this should have been "ffmpeg" all over the paragraph)

Carl Eugen

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