FFMPEG(1) FFMPEG(1)

NAME
ffmpeg - ffmpeg video converter

SYNOPSIS
ffmpeg [global_options] {[input_file_options] -i input_url} ...
{[output_file_options] output_url} ...

DESCRIPTION
ffmpeg is a very fast video and audio converter that can also grab
from a live audio/video source. It can also convert between arbitrary
sample rates and resize video on the fly with a high quality
polyphase filter.

ffmpeg reads from an arbitrary number of input "files" (which can be
regular files, pipes, network streams, grabbing devices, etc.),
specified by the "-i" option, and writes to an arbitrary number of
output "files", which are specified by a plain output url. Anything
found on the command line which cannot be interpreted as an option is
considered to be an output url.

Each input or output url can, in principle, contain any number of
streams of different types (video/audio/subtitle/attachment/data).
The allowed number and/or types of streams may be limited by the
container format. Selecting which streams from which inputs will go
into which output is either done automatically or with the "-map"
option (see the Stream selection chapter).

To refer to input files in options, you must use their indices
(0-based). E.g. the first input file is 0, the second is 1, etc.
Similarly, streams within a file are referred to by their indices.
E.g. "2:3" refers to the fourth stream in the third input file. Also
see the Stream specifiers chapter.

As a general rule, options are applied to the next specified file.
Therefore, order is important, and you can have the same option on
the command line multiple times. Each occurrence is then applied to
the next input or output file. Exceptions from this rule are the
global options (e.g. verbosity level), which should be specified
first.