@@ -26,6 +26,23 @@ avconv 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.

+avconv reads from an arbitrary number of input "files" (which can be regular

+files, pipes, network streams, grabbing devices, etc.), specified by the

+@code{-i} option, and writes to an arbitrary number of output "files", which are

+specified by a plain output filename. Anything found on the commandline which

+cannot be interpreted as an option is considered to be an output filename.

+

+Each input or output file can in principle contain any number of streams of

+different types (video/audio/subtitle/attachment/data). Allowed number and/or

+types of streams can be limited by the container format. Selecting, which

+streams from which inputs go into output, is done either automatically or with

+the @code{-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 @code{0}, the second is @code{1} etc. Similarly, streams

+within a file are referred to by their indices. E.g. @code{2:3} refers to the

+fourth stream in the third input file. See also 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

@@ -33,6 +50,10 @@ 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.

+Do not mix input and output files -- first specify all input files, then all

+output files. Also do not mix options which belong to different files. All

+options apply ONLY to the next input or output file and are reset between files.

+

 @itemize

 @item

 To set the video bitrate of the output file to 64kbit/s: