On 03/16/2020 04:37 PM, Carl Zwanzig wrote:
On 3/16/2020 6:24 AM, Gyan Doshi wrote:
-filter_complex is a global option, so parsed first, then input files, then the
complex filtergraphs are set up, then output files.
Is there any reason, then, not to always put -filter_complex as the first
parameters of the command line? The Synopsis line in the docs shows global
options first but most of the doc examples don't.
Example-
ffmpeg -i video.mkv -i image.png -filter_complex '[0:v][1:v]overlay[out]' -map
'[out]' out.mkv"
Or is there another reason for listing inputs, then -filter_complex, then
outputs?
I've been told several times by several gurus that filters, including
filter_complex, are output specific and must be specified directly before the
output to which they apply, and, for processes that have multiple outputs, can
be different for each output.
HTH,
Mark.
PS: Follow-up. Here's my style of documentation, best viewed as plain text, for
the overall structure of commands:
Basic command example:
1ST INPUT ADDITIONAL INPUTS OUTPUTS ...Note 1
ffmpeg [A] -i B [[C] -i D ...] [[E] [F] G ...]] ...Note 2
[A] -i B : the 1st input's specification.
: [A] : the 1st input's options, if any.
: B : the 1st input's URL.
[[C] -i D ...] : additional input specifications, if any.
: [C] : the 2nd input's options, if any.
: D : the 2nd input's URL.
: ... : more input specifications.
[[E] [F] G ...] : output specifications, if any.
: [E] : an output's filter chain, if any.
: [F] : an output's options, if any.
: G : an output's URL.
: ... : more output specifications.
Note 1: All inputs first, then all outputs.
Note 2: A B C D E F G are tokens that appear here simply to preserve
space.
Note 3: Global options (not shown) can be anywhere except within
another option or at the end of the command.
Note 4: Braces, [], denote options here but should not appear in actual
commands except where ffmpeg docs indicate (for example, input
and output pads in filter chains).
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