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doc/avconv: elaborate on basic functionality.
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@ -26,6 +26,23 @@ avconv is a very fast video and audio converter that can also grab from
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a live audio/video source. It can also convert between arbitrary sample
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rates and resize video on the fly with a high quality polyphase filter.
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avconv reads from an arbitrary number of input "files" (which can be regular
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files, pipes, network streams, grabbing devices, etc.), specified by the
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@code{-i} option, and writes to an arbitrary number of output "files", which are
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specified by a plain output filename. Anything found on the commandline which
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cannot be interpreted as an option is considered to be an output filename.
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Each input or output file can in principle contain any number of streams of
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different types (video/audio/subtitle/attachment/data). Allowed number and/or
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types of streams can be limited by the container format. Selecting, which
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streams from which inputs go into output, is done either automatically or with
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the @code{-map} option (see the Stream selection chapter).
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To refer to input files in options, you must use their indices (0-based). E.g.
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the first input file is @code{0}, the second is @code{1} etc. Similarly, streams
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within a file are referred to by their indices. E.g. @code{2:3} refers to the
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fourth stream in the third input file. See also the Stream specifiers chapter.
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As a general rule, options are applied to the next specified
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file. Therefore, order is important, and you can have the same
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option on the command line multiple times. Each occurrence is
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@ -33,6 +50,10 @@ then applied to the next input or output file.
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Exceptions from this rule are the global options (e.g. verbosity level),
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which should be specified first.
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Do not mix input and output files -- first specify all input files, then all
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output files. Also do not mix options which belong to different files. All
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options apply ONLY to the next input or output file and are reset between files.
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@itemize
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@item
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To set the video bitrate of the output file to 64kbit/s:
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