lavc: Add filter_units bitstream filter

[ffmpeg] / doc / ffmpeg.texi

\input texinfo @c -*- texinfo -*-
@documentencoding UTF-8

@settitle ffmpeg Documentation
@titlepage
@center @titlefont{ffmpeg Documentation}
@end titlepage

@top

@contents

@chapter Synopsis

ffmpeg [@var{global_options}] @{[@var{input_file_options}] -i @file{input_url}@} ... @{[@var{output_file_options}] @file{output_url}@} ...

@chapter Description
@c man begin DESCRIPTION

@command{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.

@command{ffmpeg} 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 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 @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. 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.

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 64 kbit/s:
@example
ffmpeg -i input.avi -b:v 64k -bufsize 64k output.avi
@end example

@item
To force the frame rate of the output file to 24 fps:
@example
ffmpeg -i input.avi -r 24 output.avi
@end example

@item
To force the frame rate of the input file (valid for raw formats only)
to 1 fps and the frame rate of the output file to 24 fps:
@example
ffmpeg -r 1 -i input.m2v -r 24 output.avi
@end example
@end itemize

The format option may be needed for raw input files.

@c man end DESCRIPTION

@chapter Detailed description
@c man begin DETAILED DESCRIPTION

The transcoding process in @command{ffmpeg} for each output can be described by
the following diagram:

@verbatim
 _______              ______________
|       |            |              |
| input |  demuxer   | encoded data |   decoder
| file  | ---------> | packets      | -----+
|_______|            |______________|      |
                                           v
                                       _________
                                      |         |
                                      | decoded |
                                      | frames  |
                                      |_________|
 ________             ______________       |
|        |           |              |      |
| output | <-------- | encoded data | <----+
| file   |   muxer   | packets      |   encoder
|________|           |______________|


@end verbatim

@command{ffmpeg} calls the libavformat library (containing demuxers) to read
input files and get packets containing encoded data from them. When there are
multiple input files, @command{ffmpeg} tries to keep them synchronized by
tracking lowest timestamp on any active input stream.

Encoded packets are then passed to the decoder (unless streamcopy is selected
for the stream, see further for a description). The decoder produces
uncompressed frames (raw video/PCM audio/...) which can be processed further by
filtering (see next section). After filtering, the frames are passed to the
encoder, which encodes them and outputs encoded packets. Finally those are
passed to the muxer, which writes the encoded packets to the output file.

@section Filtering
Before encoding, @command{ffmpeg} can process raw audio and video frames using
filters from the libavfilter library. Several chained filters form a filter
graph. @command{ffmpeg} distinguishes between two types of filtergraphs:
simple and complex.

@subsection Simple filtergraphs
Simple filtergraphs are those that have exactly one input and output, both of
the same type. In the above diagram they can be represented by simply inserting
an additional step between decoding and encoding:

@verbatim
 _________                        ______________
|         |                      |              |
| decoded |                      | encoded data |
| frames  |\                   _ | packets      |
|_________| \                  /||______________|
             \   __________   /
  simple     _\||          | /  encoder
  filtergraph   | filtered |/
                | frames   |
                |__________|

@end verbatim

Simple filtergraphs are configured with the per-stream @option{-filter} option
(with @option{-vf} and @option{-af} aliases for video and audio respectively).
A simple filtergraph for video can look for example like this:

@verbatim
 _______        _____________        _______        ________
|       |      |             |      |       |      |        |
| input | ---> | deinterlace | ---> | scale | ---> | output |
|_______|      |_____________|      |_______|      |________|

@end verbatim

Note that some filters change frame properties but not frame contents. E.g. the
@code{fps} filter in the example above changes number of frames, but does not
touch the frame contents. Another example is the @code{setpts} filter, which
only sets timestamps and otherwise passes the frames unchanged.

@subsection Complex filtergraphs
Complex filtergraphs are those which cannot be described as simply a linear
processing chain applied to one stream. This is the case, for example, when the graph has
more than one input and/or output, or when output stream type is different from
input. They can be represented with the following diagram:

@verbatim
 _________
|         |
| input 0 |\                    __________
|_________| \                  |          |
             \   _________    /| output 0 |
              \ |         |  / |__________|
 _________     \| complex | /
|         |     |         |/
| input 1 |---->| filter  |\
|_________|     |         | \   __________
               /| graph   |  \ |          |
              / |         |   \| output 1 |
 _________   /  |_________|    |__________|
|         | /
| input 2 |/
|_________|

@end verbatim

Complex filtergraphs are configured with the @option{-filter_complex} option.
Note that this option is global, since a complex filtergraph, by its nature,
cannot be unambiguously associated with a single stream or file.

The @option{-lavfi} option is equivalent to @option{-filter_complex}.

A trivial example of a complex filtergraph is the @code{overlay} filter, which
has two video inputs and one video output, containing one video overlaid on top
of the other. Its audio counterpart is the @code{amix} filter.

@section Stream copy
Stream copy is a mode selected by supplying the @code{copy} parameter to the
@option{-codec} option. It makes @command{ffmpeg} omit the decoding and encoding
step for the specified stream, so it does only demuxing and muxing. It is useful
for changing the container format or modifying container-level metadata. The
diagram above will, in this case, simplify to this:

@verbatim
 _______              ______________            ________
|       |            |              |          |        |
| input |  demuxer   | encoded data |  muxer   | output |
| file  | ---------> | packets      | -------> | file   |
|_______|            |______________|          |________|

@end verbatim

Since there is no decoding or encoding, it is very fast and there is no quality
loss. However, it might not work in some cases because of many factors. Applying
filters is obviously also impossible, since filters work on uncompressed data.

@c man end DETAILED DESCRIPTION

@chapter Stream selection
@c man begin STREAM SELECTION

By default, @command{ffmpeg} includes only one stream of each type (video, audio, subtitle)
present in the input files and adds them to each output file.  It picks the
"best" of each based upon the following criteria: for video, it is the stream
with the highest resolution, for audio, it is the stream with the most channels, for
subtitles, it is the first subtitle stream. In the case where several streams of
the same type rate equally, the stream with the lowest index is chosen.

You can disable some of those defaults by using the @code{-vn/-an/-sn/-dn} options. For
full manual control, use the @code{-map} option, which disables the defaults just
described.

@c man end STREAM SELECTION

@chapter Options
@c man begin OPTIONS

@include fftools-common-opts.texi

@section Main options

@table @option

@item -f @var{fmt} (@emph{input/output})
Force input or output file format. The format is normally auto detected for input
files and guessed from the file extension for output files, so this option is not
needed in most cases.

@item -i @var{url} (@emph{input})
input file url

@item -y (@emph{global})
Overwrite output files without asking.

@item -n (@emph{global})
Do not overwrite output files, and exit immediately if a specified
output file already exists.

@item -stream_loop @var{number} (@emph{input})
Set number of times input stream shall be looped. Loop 0 means no loop,
loop -1 means infinite loop.

@item -c[:@var{stream_specifier}] @var{codec} (@emph{input/output,per-stream})
@itemx -codec[:@var{stream_specifier}] @var{codec} (@emph{input/output,per-stream})
Select an encoder (when used before an output file) or a decoder (when used
before an input file) for one or more streams. @var{codec} is the name of a
decoder/encoder or a special value @code{copy} (output only) to indicate that
the stream is not to be re-encoded.

For example
@example
ffmpeg -i INPUT -map 0 -c:v libx264 -c:a copy OUTPUT
@end example
encodes all video streams with libx264 and copies all audio streams.

For each stream, the last matching @code{c} option is applied, so
@example
ffmpeg -i INPUT -map 0 -c copy -c:v:1 libx264 -c:a:137 libvorbis OUTPUT
@end example
will copy all the streams except the second video, which will be encoded with
libx264, and the 138th audio, which will be encoded with libvorbis.

@item -t @var{duration} (@emph{input/output})
When used as an input option (before @code{-i}), limit the @var{duration} of
data read from the input file.

When used as an output option (before an output url), stop writing the
output after its duration reaches @var{duration}.

@var{duration} must be a time duration specification,
see @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}.

-to and -t are mutually exclusive and -t has priority.

@item -to @var{position} (@emph{input/output})
Stop writing the output or reading the input at @var{position}.
@var{position} must be a time duration specification,
see @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}.

-to and -t are mutually exclusive and -t has priority.

@item -fs @var{limit_size} (@emph{output})
Set the file size limit, expressed in bytes. No further chunk of bytes is written
after the limit is exceeded. The size of the output file is slightly more than the
requested file size.

@item -ss @var{position} (@emph{input/output})
When used as an input option (before @code{-i}), seeks in this input file to
@var{position}. Note that in most formats it is not possible to seek exactly,
so @command{ffmpeg} will seek to the closest seek point before @var{position}.
When transcoding and @option{-accurate_seek} is enabled (the default), this
extra segment between the seek point and @var{position} will be decoded and
discarded. When doing stream copy or when @option{-noaccurate_seek} is used, it
will be preserved.

When used as an output option (before an output url), decodes but discards
input until the timestamps reach @var{position}.

@var{position} must be a time duration specification,
see @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}.

@item -sseof @var{position} (@emph{input/output})

Like the @code{-ss} option but relative to the "end of file". That is negative
values are earlier in the file, 0 is at EOF.

@item -itsoffset @var{offset} (@emph{input})
Set the input time offset.

@var{offset} must be a time duration specification,
see @ref{time duration syntax,,the Time duration section in the ffmpeg-utils(1) manual,ffmpeg-utils}.

The offset is added to the timestamps of the input files. Specifying
a positive offset means that the corresponding streams are delayed by
the time duration specified in @var{offset}.

@item -timestamp @var{date} (@emph{output})
Set the recording timestamp in the container.

@var{date} must be a date specification,
see @ref{date syntax,,the Date section in the ffmpeg-utils(1) manual,ffmpeg-utils}.

@item -metadata[:metadata_specifier] @var{key}=@var{value} (@emph{output,per-metadata})
Set a metadata key/value pair.

An optional @var{metadata_specifier} may be given to set metadata
on streams, chapters or programs. See @code{-map_metadata}
documentation for details.

This option overrides metadata set with @code{-map_metadata}. It is
also possible to delete metadata by using an empty value.

For example, for setting the title in the output file:
@example
ffmpeg -i in.avi -metadata title="my title" out.flv
@end example

To set the language of the first audio stream:
@example
ffmpeg -i INPUT -metadata:s:a:0 language=eng OUTPUT
@end example

@item -disposition[:stream_specifier] @var{value} (@emph{output,per-stream})
Sets the disposition for a stream.

This option overrides the disposition copied from the input stream. It is also
possible to delete the disposition by setting it to 0.

The following dispositions are recognized:
@table @option
@item default
@item dub
@item original
@item comment
@item lyrics
@item karaoke
@item forced
@item hearing_impaired
@item visual_impaired
@item clean_effects
@item captions
@item descriptions
@item metadata
@end table

For example, to make the second audio stream the default stream:
@example
ffmpeg -i in.mkv -disposition:a:1 default out.mkv
@end example

To make the second subtitle stream the default stream and remove the default
disposition from the first subtitle stream:
@example
ffmpeg -i INPUT -disposition:s:0 0 -disposition:s:1 default OUTPUT
@end example

@item -program [title=@var{title}:][program_num=@var{program_num}:]st=@var{stream}[:st=@var{stream}...] (@emph{output})

Creates a program with the specified @var{title}, @var{program_num} and adds the specified
@var{stream}(s) to it.

@item -target @var{type} (@emph{output})
Specify target file type (@code{vcd}, @code{svcd}, @code{dvd}, @code{dv},
@code{dv50}). @var{type} may be prefixed with @code{pal-}, @code{ntsc-} or
@code{film-} to use the corresponding standard. All the format options
(bitrate, codecs, buffer sizes) are then set automatically. You can just type:

@example
ffmpeg -i myfile.avi -target vcd /tmp/vcd.mpg
@end example

Nevertheless you can specify additional options as long as you know
they do not conflict with the standard, as in:

@example
ffmpeg -i myfile.avi -target vcd -bf 2 /tmp/vcd.mpg
@end example

@item -dn (@emph{output})
Disable data recording. For full manual control see the @code{-map}
option.

@item -dframes @var{number} (@emph{output})
Set the number of data frames to output. This is an obsolete alias for
@code{-frames:d}, which you should use instead.

@item -frames[:@var{stream_specifier}] @var{framecount} (@emph{output,per-stream})
Stop writing to the stream after @var{framecount} frames.

@item -q[:@var{stream_specifier}] @var{q} (@emph{output,per-stream})
@itemx -qscale[:@var{stream_specifier}] @var{q} (@emph{output,per-stream})
Use fixed quality scale (VBR). The meaning of @var{q}/@var{qscale} is
codec-dependent.
If @var{qscale} is used without a @var{stream_specifier} then it applies only
to the video stream, this is to maintain compatibility with previous behavior
and as specifying the same codec specific value to 2 different codecs that is
audio and video generally is not what is intended when no stream_specifier is
used.

@anchor{filter_option}
@item -filter[:@var{stream_specifier}] @var{filtergraph} (@emph{output,per-stream})
Create the filtergraph specified by @var{filtergraph} and use it to
filter the stream.

@var{filtergraph} is a description of the filtergraph to apply to
the stream, and must have a single input and a single output of the
same type of the stream. In the filtergraph, the input is associated
to the label @code{in}, and the output to the label @code{out}. See
the ffmpeg-filters manual for more information about the filtergraph
syntax.

See the @ref{filter_complex_option,,-filter_complex option} if you
want to create filtergraphs with multiple inputs and/or outputs.

@item -filter_script[:@var{stream_specifier}] @var{filename} (@emph{output,per-stream})
This option is similar to @option{-filter}, the only difference is that its
argument is the name of the file from which a filtergraph description is to be
read.

@item -filter_threads @var{nb_threads} (@emph{global})
Defines how many threads are used to process a filter pipeline. Each pipeline
will produce a thread pool with this many threads available for parallel processing.
The default is the number of available CPUs.

@item -pre[:@var{stream_specifier}] @var{preset_name} (@emph{output,per-stream})
Specify the preset for matching stream(s).

@item -stats (@emph{global})
Print encoding progress/statistics. It is on by default, to explicitly
disable it you need to specify @code{-nostats}.

@item -progress @var{url} (@emph{global})
Send program-friendly progress information to @var{url}.

Progress information is written approximately every second and at the end of
the encoding process. It is made of "@var{key}=@var{value}" lines. @var{key}
consists of only alphanumeric characters. The last key of a sequence of
progress information is always "progress".

@anchor{stdin option}
@item -stdin
Enable interaction on standard input. On by default unless standard input is
used as an input. To explicitly disable interaction you need to specify
@code{-nostdin}.

Disabling interaction on standard input is useful, for example, if
ffmpeg is in the background process group. Roughly the same result can
be achieved with @code{ffmpeg ... < /dev/null} but it requires a
shell.

@item -debug_ts (@emph{global})
Print timestamp information. It is off by default. This option is
mostly useful for testing and debugging purposes, and the output
format may change from one version to another, so it should not be
employed by portable scripts.

See also the option @code{-fdebug ts}.

@item -attach @var{filename} (@emph{output})
Add an attachment to the output file. This is supported by a few formats
like Matroska for e.g. fonts used in rendering subtitles. Attachments
are implemented as a specific type of stream, so this option will add
a new stream to the file. It is then possible to use per-stream options
on this stream in the usual way. Attachment streams created with this
option will be created after all the other streams (i.e. those created
with @code{-map} or automatic mappings).

Note that for Matroska you also have to set the mimetype metadata tag:
@example
ffmpeg -i INPUT -attach DejaVuSans.ttf -metadata:s:2 mimetype=application/x-truetype-font out.mkv
@end example
(assuming that the attachment stream will be third in the output file).

@item -dump_attachment[:@var{stream_specifier}] @var{filename} (@emph{input,per-stream})
Extract the matching attachment stream into a file named @var{filename}. If
@var{filename} is empty, then the value of the @code{filename} metadata tag
will be used.

E.g. to extract the first attachment to a file named 'out.ttf':
@example
ffmpeg -dump_attachment:t:0 out.ttf -i INPUT
@end example
To extract all attachments to files determined by the @code{filename} tag:
@example
ffmpeg -dump_attachment:t "" -i INPUT
@end example

Technical note -- attachments are implemented as codec extradata, so this
option can actually be used to extract extradata from any stream, not just
attachments.

@item -noautorotate
Disable automatically rotating video based on file metadata.

@end table

@section Video Options

@table @option
@item -vframes @var{number} (@emph{output})
Set the number of video frames to output. This is an obsolete alias for
@code{-frames:v}, which you should use instead.
@item -r[:@var{stream_specifier}] @var{fps} (@emph{input/output,per-stream})
Set frame rate (Hz value, fraction or abbreviation).

As an input option, ignore any timestamps stored in the file and instead
generate timestamps assuming constant frame rate @var{fps}.
This is not the same as the @option{-framerate} option used for some input formats
like image2 or v4l2 (it used to be the same in older versions of FFmpeg).
If in doubt use @option{-framerate} instead of the input option @option{-r}.

As an output option, duplicate or drop input frames to achieve constant output
frame rate @var{fps}.

@item -s[:@var{stream_specifier}] @var{size} (@emph{input/output,per-stream})
Set frame size.

As an input option, this is a shortcut for the @option{video_size} private
option, recognized by some demuxers for which the frame size is either not
stored in the file or is configurable -- e.g. raw video or video grabbers.

As an output option, this inserts the @code{scale} video filter to the
@emph{end} of the corresponding filtergraph. Please use the @code{scale} filter
directly to insert it at the beginning or some other place.

The format is @samp{wxh} (default - same as source).

@item -aspect[:@var{stream_specifier}] @var{aspect} (@emph{output,per-stream})
Set the video display aspect ratio specified by @var{aspect}.

@var{aspect} can be a floating point number string, or a string of the
form @var{num}:@var{den}, where @var{num} and @var{den} are the
numerator and denominator of the aspect ratio. For example "4:3",
"16:9", "1.3333", and "1.7777" are valid argument values.

If used together with @option{-vcodec copy}, it will affect the aspect ratio
stored at container level, but not the aspect ratio stored in encoded
frames, if it exists.

@item -vn (@emph{output})
Disable video recording. For full manual control see the @code{-map}
option.

@item -vcodec @var{codec} (@emph{output})
Set the video codec. This is an alias for @code{-codec:v}.

@item -pass[:@var{stream_specifier}] @var{n} (@emph{output,per-stream})
Select the pass number (1 or 2). It is used to do two-pass
video encoding. The statistics of the video are recorded in the first
pass into a log file (see also the option -passlogfile),
and in the second pass that log file is used to generate the video
at the exact requested bitrate.
On pass 1, you may just deactivate audio and set output to null,
examples for Windows and Unix:
@example
ffmpeg -i foo.mov -c:v libxvid -pass 1 -an -f rawvideo -y NUL
ffmpeg -i foo.mov -c:v libxvid -pass 1 -an -f rawvideo -y /dev/null
@end example

@item -passlogfile[:@var{stream_specifier}] @var{prefix} (@emph{output,per-stream})
Set two-pass log file name prefix to @var{prefix}, the default file name
prefix is ``ffmpeg2pass''. The complete file name will be
@file{PREFIX-N.log}, where N is a number specific to the output
stream

@item -vf @var{filtergraph} (@emph{output})
Create the filtergraph specified by @var{filtergraph} and use it to
filter the stream.

This is an alias for @code{-filter:v}, see the @ref{filter_option,,-filter option}.
@end table

@section Advanced Video options

@table @option
@item -pix_fmt[:@var{stream_specifier}] @var{format} (@emph{input/output,per-stream})
Set pixel format. Use @code{-pix_fmts} to show all the supported
pixel formats.
If the selected pixel format can not be selected, ffmpeg will print a
warning and select the best pixel format supported by the encoder.
If @var{pix_fmt} is prefixed by a @code{+}, ffmpeg will exit with an error
if the requested pixel format can not be selected, and automatic conversions
inside filtergraphs are disabled.
If @var{pix_fmt} is a single @code{+}, ffmpeg selects the same pixel format
as the input (or graph output) and automatic conversions are disabled.

@item -sws_flags @var{flags} (@emph{input/output})
Set SwScaler flags.
@item -vdt @var{n}
Discard threshold.

@item -rc_override[:@var{stream_specifier}] @var{override} (@emph{output,per-stream})
Rate control override for specific intervals, formatted as "int,int,int"
list separated with slashes. Two first values are the beginning and
end frame numbers, last one is quantizer to use if positive, or quality
factor if negative.

@item -ilme
Force interlacing support in encoder (MPEG-2 and MPEG-4 only).
Use this option if your input file is interlaced and you want
to keep the interlaced format for minimum losses.
The alternative is to deinterlace the input stream with
@option{-deinterlace}, but deinterlacing introduces losses.
@item -psnr
Calculate PSNR of compressed frames.
@item -vstats
Dump video coding statistics to @file{vstats_HHMMSS.log}.
@item -vstats_file @var{file}
Dump video coding statistics to @var{file}.
@item -vstats_version @var{file}
Specifies which version of the vstats format to use. Default is 2.

version = 1 :

@code{frame= %5d q= %2.1f PSNR= %6.2f f_size= %6d s_size= %8.0fkB time= %0.3f br= %7.1fkbits/s avg_br= %7.1fkbits/s}

version > 1:

@code{out= %2d st= %2d frame= %5d q= %2.1f PSNR= %6.2f f_size= %6d s_size= %8.0fkB time= %0.3f br= %7.1fkbits/s avg_br= %7.1fkbits/s}
@item -top[:@var{stream_specifier}] @var{n} (@emph{output,per-stream})
top=1/bottom=0/auto=-1 field first
@item -dc @var{precision}
Intra_dc_precision.
@item -vtag @var{fourcc/tag} (@emph{output})
Force video tag/fourcc. This is an alias for @code{-tag:v}.
@item -qphist (@emph{global})
Show QP histogram
@item -vbsf @var{bitstream_filter}
Deprecated see -bsf

@item -force_key_frames[:@var{stream_specifier}] @var{time}[,@var{time}...] (@emph{output,per-stream})
@item -force_key_frames[:@var{stream_specifier}] expr:@var{expr} (@emph{output,per-stream})
Force key frames at the specified timestamps, more precisely at the first
frames after each specified time.

If the argument is prefixed with @code{expr:}, the string @var{expr}
is interpreted like an expression and is evaluated for each frame. A
key frame is forced in case the evaluation is non-zero.

If one of the times is "@code{chapters}[@var{delta}]", it is expanded into
the time of the beginning of all chapters in the file, shifted by
@var{delta}, expressed as a time in seconds.
This option can be useful to ensure that a seek point is present at a
chapter mark or any other designated place in the output file.

For example, to insert a key frame at 5 minutes, plus key frames 0.1 second
before the beginning of every chapter:
@example
-force_key_frames 0:05:00,chapters-0.1
@end example

The expression in @var{expr} can contain the following constants:
@table @option
@item n
the number of current processed frame, starting from 0
@item n_forced
the number of forced frames
@item prev_forced_n
the number of the previous forced frame, it is @code{NAN} when no
keyframe was forced yet
@item prev_forced_t
the time of the previous forced frame, it is @code{NAN} when no
keyframe was forced yet
@item t
the time of the current processed frame
@end table

For example to force a key frame every 5 seconds, you can specify:
@example
-force_key_frames expr:gte(t,n_forced*5)
@end example

To force a key frame 5 seconds after the time of the last forced one,
starting from second 13:
@example
-force_key_frames expr:if(isnan(prev_forced_t),gte(t,13),gte(t,prev_forced_t+5))
@end example

Note that forcing too many keyframes is very harmful for the lookahead
algorithms of certain encoders: using fixed-GOP options or similar
would be more efficient.

@item -copyinkf[:@var{stream_specifier}] (@emph{output,per-stream})
When doing stream copy, copy also non-key frames found at the
beginning.

@item -init_hw_device @var{type}[=@var{name}][:@var{device}[,@var{key=value}...]]
Initialise a new hardware device of type @var{type} called @var{name}, using the
given device parameters.
If no name is specified it will receive a default name of the form "@var{type}%d".

The meaning of @var{device} and the following arguments depends on the
device type:
@table @option

@item cuda
@var{device} is the number of the CUDA device.

@item dxva2
@var{device} is the number of the Direct3D 9 display adapter.

@item vaapi
@var{device} is either an X11 display name or a DRM render node.
If not specified, it will attempt to open the default X11 display (@emph{$DISPLAY})
and then the first DRM render node (@emph{/dev/dri/renderD128}).

@item vdpau
@var{device} is an X11 display name.
If not specified, it will attempt to open the default X11 display (@emph{$DISPLAY}).

@item qsv
@var{device} selects a value in @samp{MFX_IMPL_*}. Allowed values are:
@table @option
@item auto
@item sw
@item hw
@item auto_any
@item hw_any
@item hw2
@item hw3
@item hw4
@end table
If not specified, @samp{auto_any} is used.
(Note that it may be easier to achieve the desired result for QSV by creating the
platform-appropriate subdevice (@samp{dxva2} or @samp{vaapi}) and then deriving a
QSV device from that.)

@item opencl
@var{device} selects the platform and device as @emph{platform_index.device_index}.

The set of devices can also be filtered using the key-value pairs to find only
devices matching particular platform or device strings.

The strings usable as filters are:
@table @option
@item platform_profile
@item platform_version
@item platform_name
@item platform_vendor
@item platform_extensions
@item device_name
@item device_vendor
@item driver_version
@item device_version
@item device_profile
@item device_extensions
@item device_type
@end table

The indices and filters must together uniquely select a device.

Examples:
@table @emph
@item -init_hw_device opencl:0.1
Choose the second device on the first platform.

@item -init_hw_device opencl:,device_name=Foo9000
Choose the device with a name containing the string @emph{Foo9000}.

@item -init_hw_device opencl:1,device_type=gpu,device_extensions=cl_khr_fp16
Choose the GPU device on the second platform supporting the @emph{cl_khr_fp16}
extension.
@end table

@end table

@item -init_hw_device @var{type}[=@var{name}]@@@var{source}
Initialise a new hardware device of type @var{type} called @var{name},
deriving it from the existing device with the name @var{source}.

@item -init_hw_device list
List all hardware device types supported in this build of ffmpeg.

@item -filter_hw_device @var{name}
Pass the hardware device called @var{name} to all filters in any filter graph.
This can be used to set the device to upload to with the @code{hwupload} filter,
or the device to map to with the @code{hwmap} filter.  Other filters may also
make use of this parameter when they require a hardware device.  Note that this
is typically only required when the input is not already in hardware frames -
when it is, filters will derive the device they require from the context of the
frames they receive as input.

This is a global setting, so all filters will receive the same device.

@item -hwaccel[:@var{stream_specifier}] @var{hwaccel} (@emph{input,per-stream})
Use hardware acceleration to decode the matching stream(s). The allowed values
of @var{hwaccel} are:
@table @option
@item none
Do not use any hardware acceleration (the default).

@item auto
Automatically select the hardware acceleration method.

@item vdpau
Use VDPAU (Video Decode and Presentation API for Unix) hardware acceleration.

@item dxva2
Use DXVA2 (DirectX Video Acceleration) hardware acceleration.

@item vaapi
Use VAAPI (Video Acceleration API) hardware acceleration.

@item qsv
Use the Intel QuickSync Video acceleration for video transcoding.

Unlike most other values, this option does not enable accelerated decoding (that
is used automatically whenever a qsv decoder is selected), but accelerated
transcoding, without copying the frames into the system memory.

For it to work, both the decoder and the encoder must support QSV acceleration
and no filters must be used.
@end table

This option has no effect if the selected hwaccel is not available or not
supported by the chosen decoder.

Note that most acceleration methods are intended for playback and will not be
faster than software decoding on modern CPUs. Additionally, @command{ffmpeg}
will usually need to copy the decoded frames from the GPU memory into the system
memory, resulting in further performance loss. This option is thus mainly
useful for testing.

@item -hwaccel_device[:@var{stream_specifier}] @var{hwaccel_device} (@emph{input,per-stream})
Select a device to use for hardware acceleration.

This option only makes sense when the @option{-hwaccel} option is also specified.
It can either refer to an existing device created with @option{-init_hw_device}
by name, or it can create a new device as if
@samp{-init_hw_device} @var{type}:@var{hwaccel_device}
were called immediately before.

@item -hwaccels
List all hardware acceleration methods supported in this build of ffmpeg.

@end table

@section Audio Options

@table @option
@item -aframes @var{number} (@emph{output})
Set the number of audio frames to output. This is an obsolete alias for
@code{-frames:a}, which you should use instead.
@item -ar[:@var{stream_specifier}] @var{freq} (@emph{input/output,per-stream})
Set the audio sampling frequency. For output streams it is set by
default to the frequency of the corresponding input stream. For input
streams this option only makes sense for audio grabbing devices and raw
demuxers and is mapped to the corresponding demuxer options.
@item -aq @var{q} (@emph{output})
Set the audio quality (codec-specific, VBR). This is an alias for -q:a.
@item -ac[:@var{stream_specifier}] @var{channels} (@emph{input/output,per-stream})
Set the number of audio channels. For output streams it is set by
default to the number of input audio channels. For input streams
this option only makes sense for audio grabbing devices and raw demuxers
and is mapped to the corresponding demuxer options.
@item -an (@emph{output})
Disable audio recording. For full manual control see the @code{-map}
option.
@item -acodec @var{codec} (@emph{input/output})
Set the audio codec. This is an alias for @code{-codec:a}.
@item -sample_fmt[:@var{stream_specifier}] @var{sample_fmt} (@emph{output,per-stream})
Set the audio sample format. Use @code{-sample_fmts} to get a list
of supported sample formats.

@item -af @var{filtergraph} (@emph{output})
Create the filtergraph specified by @var{filtergraph} and use it to
filter the stream.

This is an alias for @code{-filter:a}, see the @ref{filter_option,,-filter option}.
@end table

@section Advanced Audio options

@table @option
@item -atag @var{fourcc/tag} (@emph{output})
Force audio tag/fourcc. This is an alias for @code{-tag:a}.
@item -absf @var{bitstream_filter}
Deprecated, see -bsf
@item -guess_layout_max @var{channels} (@emph{input,per-stream})
If some input channel layout is not known, try to guess only if it
corresponds to at most the specified number of channels. For example, 2
tells to @command{ffmpeg} to recognize 1 channel as mono and 2 channels as
stereo but not 6 channels as 5.1. The default is to always try to guess. Use
0 to disable all guessing.
@end table

@section Subtitle options

@table @option
@item -scodec @var{codec} (@emph{input/output})
Set the subtitle codec. This is an alias for @code{-codec:s}.
@item -sn (@emph{output})
Disable subtitle recording. For full manual control see the @code{-map}
option.
@item -sbsf @var{bitstream_filter}
Deprecated, see -bsf
@end table

@section Advanced Subtitle options

@table @option

@item -fix_sub_duration
Fix subtitles durations. For each subtitle, wait for the next packet in the
same stream and adjust the duration of the first to avoid overlap. This is
necessary with some subtitles codecs, especially DVB subtitles, because the
duration in the original packet is only a rough estimate and the end is
actually marked by an empty subtitle frame. Failing to use this option when
necessary can result in exaggerated durations or muxing failures due to
non-monotonic timestamps.

Note that this option will delay the output of all data until the next
subtitle packet is decoded: it may increase memory consumption and latency a
lot.

@item -canvas_size @var{size}
Set the size of the canvas used to render subtitles.

@end table

@section Advanced options

@table @option
@item -map [-]@var{input_file_id}[:@var{stream_specifier}][?][,@var{sync_file_id}[:@var{stream_specifier}]] | @var{[linklabel]} (@emph{output})

Designate one or more input streams as a source for the output file. Each input
stream is identified by the input file index @var{input_file_id} and
the input stream index @var{input_stream_id} within the input
file. Both indices start at 0. If specified,
@var{sync_file_id}:@var{stream_specifier} sets which input stream
is used as a presentation sync reference.

The first @code{-map} option on the command line specifies the
source for output stream 0, the second @code{-map} option specifies
the source for output stream 1, etc.

A @code{-} character before the stream identifier creates a "negative" mapping.
It disables matching streams from already created mappings.

A trailing @code{?} after the stream index will allow the map to be
optional: if the map matches no streams the map will be ignored instead
of failing. Note the map will still fail if an invalid input file index
is used; such as if the map refers to a non-existent input.

An alternative @var{[linklabel]} form will map outputs from complex filter
graphs (see the @option{-filter_complex} option) to the output file.
@var{linklabel} must correspond to a defined output link label in the graph.

For example, to map ALL streams from the first input file to output
@example
ffmpeg -i INPUT -map 0 output
@end example

For example, if you have two audio streams in the first input file,
these streams are identified by "0:0" and "0:1". You can use
@code{-map} to select which streams to place in an output file. For
example:
@example
ffmpeg -i INPUT -map 0:1 out.wav
@end example
will map the input stream in @file{INPUT} identified by "0:1" to
the (single) output stream in @file{out.wav}.

For example, to select the stream with index 2 from input file
@file{a.mov} (specified by the identifier "0:2"), and stream with
index 6 from input @file{b.mov} (specified by the identifier "1:6"),
and copy them to the output file @file{out.mov}:
@example
ffmpeg -i a.mov -i b.mov -c copy -map 0:2 -map 1:6 out.mov
@end example

To select all video and the third audio stream from an input file:
@example
ffmpeg -i INPUT -map 0:v -map 0:a:2 OUTPUT
@end example

To map all the streams except the second audio, use negative mappings
@example
ffmpeg -i INPUT -map 0 -map -0:a:1 OUTPUT
@end example

To map the video and audio streams from the first input, and using the
trailing @code{?}, ignore the audio mapping if no audio streams exist in
the first input:
@example
ffmpeg -i INPUT -map 0:v -map 0:a? OUTPUT
@end example

To pick the English audio stream:
@example
ffmpeg -i INPUT -map 0:m:language:eng OUTPUT
@end example

Note that using this option disables the default mappings for this output file.

@item -ignore_unknown
Ignore input streams with unknown type instead of failing if copying
such streams is attempted.

@item -copy_unknown
Allow input streams with unknown type to be copied instead of failing if copying
such streams is attempted.

@item -map_channel [@var{input_file_id}.@var{stream_specifier}.@var{channel_id}|-1][?][:@var{output_file_id}.@var{stream_specifier}]
Map an audio channel from a given input to an output. If
@var{output_file_id}.@var{stream_specifier} is not set, the audio channel will
be mapped on all the audio streams.

Using "-1" instead of
@var{input_file_id}.@var{stream_specifier}.@var{channel_id} will map a muted
channel.

A trailing @code{?} will allow the map_channel to be
optional: if the map_channel matches no channel the map_channel will be ignored instead
of failing.

For example, assuming @var{INPUT} is a stereo audio file, you can switch the
two audio channels with the following command:
@example
ffmpeg -i INPUT -map_channel 0.0.1 -map_channel 0.0.0 OUTPUT
@end example

If you want to mute the first channel and keep the second:
@example
ffmpeg -i INPUT -map_channel -1 -map_channel 0.0.1 OUTPUT
@end example

The order of the "-map_channel" option specifies the order of the channels in
the output stream. The output channel layout is guessed from the number of
channels mapped (mono if one "-map_channel", stereo if two, etc.). Using "-ac"
in combination of "-map_channel" makes the channel gain levels to be updated if
input and output channel layouts don't match (for instance two "-map_channel"
options and "-ac 6").

You can also extract each channel of an input to specific outputs; the following
command extracts two channels of the @var{INPUT} audio stream (file 0, stream 0)
to the respective @var{OUTPUT_CH0} and @var{OUTPUT_CH1} outputs:
@example
ffmpeg -i INPUT -map_channel 0.0.0 OUTPUT_CH0 -map_channel 0.0.1 OUTPUT_CH1
@end example

The following example splits the channels of a stereo input into two separate
streams, which are put into the same output file:
@example
ffmpeg -i stereo.wav -map 0:0 -map 0:0 -map_channel 0.0.0:0.0 -map_channel 0.0.1:0.1 -y out.ogg
@end example

Note that currently each output stream can only contain channels from a single
input stream; you can't for example use "-map_channel" to pick multiple input
audio channels contained in different streams (from the same or different files)
and merge them into a single output stream. It is therefore not currently
possible, for example, to turn two separate mono streams into a single stereo
stream. However splitting a stereo stream into two single channel mono streams
is possible.

If you need this feature, a possible workaround is to use the @emph{amerge}
filter. For example, if you need to merge a media (here @file{input.mkv}) with 2
mono audio streams into one single stereo channel audio stream (and keep the
video stream), you can use the following command:
@example
ffmpeg -i input.mkv -filter_complex "[0:1] [0:2] amerge" -c:a pcm_s16le -c:v copy output.mkv
@end example

To map the first two audio channels from the first input, and using the
trailing @code{?}, ignore the audio channel mapping if the first input is
mono instead of stereo:
@example
ffmpeg -i INPUT -map_channel 0.0.0 -map_channel 0.0.1? OUTPUT
@end example

@item -map_metadata[:@var{metadata_spec_out}] @var{infile}[:@var{metadata_spec_in}] (@emph{output,per-metadata})
Set metadata information of the next output file from @var{infile}. Note that
those are file indices (zero-based), not filenames.
Optional @var{metadata_spec_in/out} parameters specify, which metadata to copy.
A metadata specifier can have the following forms:
@table @option
@item @var{g}
global metadata, i.e. metadata that applies to the whole file

@item @var{s}[:@var{stream_spec}]
per-stream metadata. @var{stream_spec} is a stream specifier as described
in the @ref{Stream specifiers} chapter. In an input metadata specifier, the first
matching stream is copied from. In an output metadata specifier, all matching
streams are copied to.

@item @var{c}:@var{chapter_index}
per-chapter metadata. @var{chapter_index} is the zero-based chapter index.

@item @var{p}:@var{program_index}
per-program metadata. @var{program_index} is the zero-based program index.
@end table
If metadata specifier is omitted, it defaults to global.

By default, global metadata is copied from the first input file,
per-stream and per-chapter metadata is copied along with streams/chapters. These
default mappings are disabled by creating any mapping of the relevant type. A negative
file index can be used to create a dummy mapping that just disables automatic copying.

For example to copy metadata from the first stream of the input file to global metadata
of the output file:
@example
ffmpeg -i in.ogg -map_metadata 0:s:0 out.mp3
@end example

To do the reverse, i.e. copy global metadata to all audio streams:
@example
ffmpeg -i in.mkv -map_metadata:s:a 0:g out.mkv
@end example
Note that simple @code{0} would work as well in this example, since global
metadata is assumed by default.

@item -map_chapters @var{input_file_index} (@emph{output})
Copy chapters from input file with index @var{input_file_index} to the next
output file. If no chapter mapping is specified, then chapters are copied from
the first input file with at least one chapter. Use a negative file index to
disable any chapter copying.

@item -benchmark (@emph{global})
Show benchmarking information at the end of an encode.
Shows CPU time used and maximum memory consumption.
Maximum memory consumption is not supported on all systems,
it will usually display as 0 if not supported.
@item -benchmark_all (@emph{global})
Show benchmarking information during the encode.
Shows CPU time used in various steps (audio/video encode/decode).
@item -timelimit @var{duration} (@emph{global})
Exit after ffmpeg has been running for @var{duration} seconds.
@item -dump (@emph{global})
Dump each input packet to stderr.
@item -hex (@emph{global})
When dumping packets, also dump the payload.
@item -re (@emph{input})
Read input at native frame rate. Mainly used to simulate a grab device,
or live input stream (e.g. when reading from a file). Should not be used
with actual grab devices or live input streams (where it can cause packet
loss).
By default @command{ffmpeg} attempts to read the input(s) as fast as possible.
This option will slow down the reading of the input(s) to the native frame rate
of the input(s). It is useful for real-time output (e.g. live streaming).
@item -loop_output @var{number_of_times}
Repeatedly loop output for formats that support looping such as animated GIF
(0 will loop the output infinitely).
This option is deprecated, use -loop.
@item -vsync @var{parameter}
Video sync method.
For compatibility reasons old values can be specified as numbers.
Newly added values will have to be specified as strings always.

@table @option
@item 0, passthrough
Each frame is passed with its timestamp from the demuxer to the muxer.
@item 1, cfr
Frames will be duplicated and dropped to achieve exactly the requested
constant frame rate.
@item 2, vfr
Frames are passed through with their timestamp or dropped so as to
prevent 2 frames from having the same timestamp.
@item drop
As passthrough but destroys all timestamps, making the muxer generate
fresh timestamps based on frame-rate.
@item -1, auto
Chooses between 1 and 2 depending on muxer capabilities. This is the
default method.
@end table

Note that the timestamps may be further modified by the muxer, after this.
For example, in the case that the format option @option{avoid_negative_ts}
is enabled.

With -map you can select from which stream the timestamps should be
taken. You can leave either video or audio unchanged and sync the
remaining stream(s) to the unchanged one.

@item -frame_drop_threshold @var{parameter}
Frame drop threshold, which specifies how much behind video frames can
be before they are dropped. In frame rate units, so 1.0 is one frame.
The default is -1.1. One possible usecase is to avoid framedrops in case
of noisy timestamps or to increase frame drop precision in case of exact
timestamps.

@item -async @var{samples_per_second}
Audio sync method. "Stretches/squeezes" the audio stream to match the timestamps,
the parameter is the maximum samples per second by which the audio is changed.
-async 1 is a special case where only the start of the audio stream is corrected
without any later correction.

Note that the timestamps may be further modified by the muxer, after this.
For example, in the case that the format option @option{avoid_negative_ts}
is enabled.

This option has been deprecated. Use the @code{aresample} audio filter instead.

@item -copyts
Do not process input timestamps, but keep their values without trying
to sanitize them. In particular, do not remove the initial start time
offset value.

Note that, depending on the @option{vsync} option or on specific muxer
processing (e.g. in case the format option @option{avoid_negative_ts}
is enabled) the output timestamps may mismatch with the input
timestamps even when this option is selected.

@item -start_at_zero
When used with @option{copyts}, shift input timestamps so they start at zero.

This means that using e.g. @code{-ss 50} will make output timestamps start at
50 seconds, regardless of what timestamp the input file started at.

@item -copytb @var{mode}
Specify how to set the encoder timebase when stream copying.  @var{mode} is an
integer numeric value, and can assume one of the following values:

@table @option
@item 1
Use the demuxer timebase.

The time base is copied to the output encoder from the corresponding input
demuxer. This is sometimes required to avoid non monotonically increasing
timestamps when copying video streams with variable frame rate.

@item 0
Use the decoder timebase.

The time base is copied to the output encoder from the corresponding input
decoder.

@item -1
Try to make the choice automatically, in order to generate a sane output.
@end table

Default value is -1.

@item -enc_time_base[:@var{stream_specifier}] @var{timebase} (@emph{output,per-stream})
Set the encoder timebase. @var{timebase} is a floating point number,
and can assume one of the following values:

@table @option
@item 0
Assign a default value according to the media type.

For video - use 1/framerate, for audio - use 1/samplerate.

@item -1
Use the input stream timebase when possible.

If an input stream is not available, the default timebase will be used.

@item >0
Use the provided number as the timebase.

This field can be provided as a ratio of two integers (e.g. 1:24, 1:48000)
or as a floating point number (e.g. 0.04166, 2.0833e-5)
@end table

Default value is 0.

@item -bitexact (@emph{input/output})
Enable bitexact mode for (de)muxer and (de/en)coder
@item -shortest (@emph{output})
Finish encoding when the shortest input stream ends.
@item -dts_delta_threshold
Timestamp discontinuity delta threshold.
@item -muxdelay @var{seconds} (@emph{input})
Set the maximum demux-decode delay.
@item -muxpreload @var{seconds} (@emph{input})
Set the initial demux-decode delay.
@item -streamid @var{output-stream-index}:@var{new-value} (@emph{output})
Assign a new stream-id value to an output stream. This option should be
specified prior to the output filename to which it applies.
For the situation where multiple output files exist, a streamid
may be reassigned to a different value.

For example, to set the stream 0 PID to 33 and the stream 1 PID to 36 for
an output mpegts file:
@example
ffmpeg -i inurl -streamid 0:33 -streamid 1:36 out.ts
@end example

@item -bsf[:@var{stream_specifier}] @var{bitstream_filters} (@emph{output,per-stream})
Set bitstream filters for matching streams. @var{bitstream_filters} is
a comma-separated list of bitstream filters. Use the @code{-bsfs} option
to get the list of bitstream filters.
@example
ffmpeg -i h264.mp4 -c:v copy -bsf:v h264_mp4toannexb -an out.h264
@end example
@example
ffmpeg -i file.mov -an -vn -bsf:s mov2textsub -c:s copy -f rawvideo sub.txt
@end example

@item -tag[:@var{stream_specifier}] @var{codec_tag} (@emph{input/output,per-stream})
Force a tag/fourcc for matching streams.

@item -timecode @var{hh}:@var{mm}:@var{ss}SEP@var{ff}
Specify Timecode for writing. @var{SEP} is ':' for non drop timecode and ';'
(or '.') for drop.
@example
ffmpeg -i input.mpg -timecode 01:02:03.04 -r 30000/1001 -s ntsc output.mpg
@end example

@anchor{filter_complex_option}
@item -filter_complex @var{filtergraph} (@emph{global})
Define a complex filtergraph, i.e. one with arbitrary number of inputs and/or
outputs. For simple graphs -- those with one input and one output of the same
type -- see the @option{-filter} options. @var{filtergraph} is a description of
the filtergraph, as described in the ``Filtergraph syntax'' section of the
ffmpeg-filters manual.

Input link labels must refer to input streams using the
@code{[file_index:stream_specifier]} syntax (i.e. the same as @option{-map}
uses). If @var{stream_specifier} matches multiple streams, the first one will be
used. An unlabeled input will be connected to the first unused input stream of
the matching type.

Output link labels are referred to with @option{-map}. Unlabeled outputs are
added to the first output file.

Note that with this option it is possible to use only lavfi sources without
normal input files.

For example, to overlay an image over video
@example
ffmpeg -i video.mkv -i image.png -filter_complex '[0:v][1:v]overlay[out]' -map
'[out]' out.mkv
@end example
Here @code{[0:v]} refers to the first video stream in the first input file,
which is linked to the first (main) input of the overlay filter. Similarly the
first video stream in the second input is linked to the second (overlay) input
of overlay.

Assuming there is only one video stream in each input file, we can omit input
labels, so the above is equivalent to
@example
ffmpeg -i video.mkv -i image.png -filter_complex 'overlay[out]' -map
'[out]' out.mkv
@end example

Furthermore we can omit the output label and the single output from the filter
graph will be added to the output file automatically, so we can simply write
@example
ffmpeg -i video.mkv -i image.png -filter_complex 'overlay' out.mkv
@end example

To generate 5 seconds of pure red video using lavfi @code{color} source:
@example
ffmpeg -filter_complex 'color=c=red' -t 5 out.mkv
@end example

@item -filter_complex_threads @var{nb_threads} (@emph{global})
Defines how many threads are used to process a filter_complex graph.
Similar to filter_threads but used for @code{-filter_complex} graphs only.
The default is the number of available CPUs.

@item -lavfi @var{filtergraph} (@emph{global})
Define a complex filtergraph, i.e. one with arbitrary number of inputs and/or
outputs. Equivalent to @option{-filter_complex}.

@item -filter_complex_script @var{filename} (@emph{global})
This option is similar to @option{-filter_complex}, the only difference is that
its argument is the name of the file from which a complex filtergraph
description is to be read.

@item -accurate_seek (@emph{input})
This option enables or disables accurate seeking in input files with the
@option{-ss} option. It is enabled by default, so seeking is accurate when
transcoding. Use @option{-noaccurate_seek} to disable it, which may be useful
e.g. when copying some streams and transcoding the others.

@item -seek_timestamp (@emph{input})
This option enables or disables seeking by timestamp in input files with the
@option{-ss} option. It is disabled by default. If enabled, the argument
to the @option{-ss} option is considered an actual timestamp, and is not
offset by the start time of the file. This matters only for files which do
not start from timestamp 0, such as transport streams.

@item -thread_queue_size @var{size} (@emph{input})
This option sets the maximum number of queued packets when reading from the
file or device. With low latency / high rate live streams, packets may be
discarded if they are not read in a timely manner; raising this value can
avoid it.

@item -sdp_file @var{file} (@emph{global})
Print sdp information for an output stream to @var{file}.
This allows dumping sdp information when at least one output isn't an
rtp stream. (Requires at least one of the output formats to be rtp).

@item -discard (@emph{input})
Allows discarding specific streams or frames of streams at the demuxer.
Not all demuxers support this.

@table @option
@item none
Discard no frame.

@item default
Default, which discards no frames.

@item noref
Discard all non-reference frames.

@item bidir
Discard all bidirectional frames.

@item nokey
Discard all frames excepts keyframes.

@item all
Discard all frames.
@end table

@item -abort_on @var{flags} (@emph{global})
Stop and abort on various conditions. The following flags are available:

@table @option
@item empty_output
No packets were passed to the muxer, the output is empty.
@end table

@item -xerror (@emph{global})
Stop and exit on error

@item -max_muxing_queue_size @var{packets} (@emph{output,per-stream})
When transcoding audio and/or video streams, ffmpeg will not begin writing into
the output until it has one packet for each such stream. While waiting for that
to happen, packets for other streams are buffered. This option sets the size of
this buffer, in packets, for the matching output stream.

The default value of this option should be high enough for most uses, so only
touch this option if you are sure that you need it.

@end table

As a special exception, you can use a bitmap subtitle stream as input: it
will be converted into a video with the same size as the largest video in
the file, or 720x576 if no video is present. Note that this is an
experimental and temporary solution. It will be removed once libavfilter has
proper support for subtitles.

For example, to hardcode subtitles on top of a DVB-T recording stored in
MPEG-TS format, delaying the subtitles by 1 second:
@example
ffmpeg -i input.ts -filter_complex \
  '[#0x2ef] setpts=PTS+1/TB [sub] ; [#0x2d0] [sub] overlay' \
  -sn -map '#0x2dc' output.mkv
@end example
(0x2d0, 0x2dc and 0x2ef are the MPEG-TS PIDs of respectively the video,
audio and subtitles streams; 0:0, 0:3 and 0:7 would have worked too)

@section Preset files
A preset file contains a sequence of @var{option}=@var{value} pairs,
one for each line, specifying a sequence of options which would be
awkward to specify on the command line. Lines starting with the hash
('#') character are ignored and are used to provide comments. Check
the @file{presets} directory in the FFmpeg source tree for examples.

There are two types of preset files: ffpreset and avpreset files.

@subsection ffpreset files
ffpreset files are specified with the @code{vpre}, @code{apre},
@code{spre}, and @code{fpre} options. The @code{fpre} option takes the
filename of the preset instead of a preset name as input and can be
used for any kind of codec. For the @code{vpre}, @code{apre}, and
@code{spre} options, the options specified in a preset file are
applied to the currently selected codec of the same type as the preset
option.

The argument passed to the @code{vpre}, @code{apre}, and @code{spre}
preset options identifies the preset file to use according to the
following rules:

First ffmpeg searches for a file named @var{arg}.ffpreset in the
directories @file{$FFMPEG_DATADIR} (if set), and @file{$HOME/.ffmpeg}, and in
the datadir defined at configuration time (usually @file{PREFIX/share/ffmpeg})
or in a @file{ffpresets} folder along the executable on win32,
in that order. For example, if the argument is @code{libvpx-1080p}, it will
search for the file @file{libvpx-1080p.ffpreset}.

If no such file is found, then ffmpeg will search for a file named
@var{codec_name}-@var{arg}.ffpreset in the above-mentioned
directories, where @var{codec_name} is the name of the codec to which
the preset file options will be applied. For example, if you select
the video codec with @code{-vcodec libvpx} and use @code{-vpre 1080p},
then it will search for the file @file{libvpx-1080p.ffpreset}.

@subsection avpreset files
avpreset files are specified with the @code{pre} option. They work similar to
ffpreset files, but they only allow encoder- specific options. Therefore, an
@var{option}=@var{value} pair specifying an encoder cannot be used.

When the @code{pre} option is specified, ffmpeg will look for files with the
suffix .avpreset in the directories @file{$AVCONV_DATADIR} (if set), and
@file{$HOME/.avconv}, and in the datadir defined at configuration time (usually
@file{PREFIX/share/ffmpeg}), in that order.

First ffmpeg searches for a file named @var{codec_name}-@var{arg}.avpreset in
the above-mentioned directories, where @var{codec_name} is the name of the codec
to which the preset file options will be applied. For example, if you select the
video codec with @code{-vcodec libvpx} and use @code{-pre 1080p}, then it will
search for the file @file{libvpx-1080p.avpreset}.

If no such file is found, then ffmpeg will search for a file named
@var{arg}.avpreset in the same directories.

@c man end OPTIONS

@chapter Examples
@c man begin EXAMPLES

@section Video and Audio grabbing

If you specify the input format and device then ffmpeg can grab video
and audio directly.

@example
ffmpeg -f oss -i /dev/dsp -f video4linux2 -i /dev/video0 /tmp/out.mpg
@end example

Or with an ALSA audio source (mono input, card id 1) instead of OSS:
@example
ffmpeg -f alsa -ac 1 -i hw:1 -f video4linux2 -i /dev/video0 /tmp/out.mpg
@end example

Note that you must activate the right video source and channel before
launching ffmpeg with any TV viewer such as
@uref{http://linux.bytesex.org/xawtv/, xawtv} by Gerd Knorr. You also
have to set the audio recording levels correctly with a
standard mixer.

@section X11 grabbing

Grab the X11 display with ffmpeg via

@example
ffmpeg -f x11grab -video_size cif -framerate 25 -i :0.0 /tmp/out.mpg
@end example

0.0 is display.screen number of your X11 server, same as
the DISPLAY environment variable.

@example
ffmpeg -f x11grab -video_size cif -framerate 25 -i :0.0+10,20 /tmp/out.mpg
@end example

0.0 is display.screen number of your X11 server, same as the DISPLAY environment
variable. 10 is the x-offset and 20 the y-offset for the grabbing.

@section Video and Audio file format conversion

Any supported file format and protocol can serve as input to ffmpeg:

Examples:
@itemize
@item
You can use YUV files as input:

@example
ffmpeg -i /tmp/test%d.Y /tmp/out.mpg
@end example

It will use the files:
@example
/tmp/test0.Y, /tmp/test0.U, /tmp/test0.V,
/tmp/test1.Y, /tmp/test1.U, /tmp/test1.V, etc...
@end example

The Y files use twice the resolution of the U and V files. They are
raw files, without header. They can be generated by all decent video
decoders. You must specify the size of the image with the @option{-s} option
if ffmpeg cannot guess it.

@item
You can input from a raw YUV420P file:

@example
ffmpeg -i /tmp/test.yuv /tmp/out.avi
@end example

test.yuv is a file containing raw YUV planar data. Each frame is composed
of the Y plane followed by the U and V planes at half vertical and
horizontal resolution.

@item
You can output to a raw YUV420P file:

@example
ffmpeg -i mydivx.avi hugefile.yuv
@end example

@item
You can set several input files and output files:

@example
ffmpeg -i /tmp/a.wav -s 640x480 -i /tmp/a.yuv /tmp/a.mpg
@end example

Converts the audio file a.wav and the raw YUV video file a.yuv
to MPEG file a.mpg.

@item
You can also do audio and video conversions at the same time:

@example
ffmpeg -i /tmp/a.wav -ar 22050 /tmp/a.mp2
@end example

Converts a.wav to MPEG audio at 22050 Hz sample rate.

@item
You can encode to several formats at the same time and define a
mapping from input stream to output streams:

@example
ffmpeg -i /tmp/a.wav -map 0:a -b:a 64k /tmp/a.mp2 -map 0:a -b:a 128k /tmp/b.mp2
@end example

Converts a.wav to a.mp2 at 64 kbits and to b.mp2 at 128 kbits. '-map
file:index' specifies which input stream is used for each output
stream, in the order of the definition of output streams.

@item
You can transcode decrypted VOBs:

@example
ffmpeg -i snatch_1.vob -f avi -c:v mpeg4 -b:v 800k -g 300 -bf 2 -c:a libmp3lame -b:a 128k snatch.avi
@end example

This is a typical DVD ripping example; the input is a VOB file, the
output an AVI file with MPEG-4 video and MP3 audio. Note that in this
command we use B-frames so the MPEG-4 stream is DivX5 compatible, and
GOP size is 300 which means one intra frame every 10 seconds for 29.97fps
input video. Furthermore, the audio stream is MP3-encoded so you need
to enable LAME support by passing @code{--enable-libmp3lame} to configure.
The mapping is particularly useful for DVD transcoding
to get the desired audio language.

NOTE: To see the supported input formats, use @code{ffmpeg -demuxers}.

@item
You can extract images from a video, or create a video from many images:

For extracting images from a video:
@example
ffmpeg -i foo.avi -r 1 -s WxH -f image2 foo-%03d.jpeg
@end example

This will extract one video frame per second from the video and will
output them in files named @file{foo-001.jpeg}, @file{foo-002.jpeg},
etc. Images will be rescaled to fit the new WxH values.

If you want to extract just a limited number of frames, you can use the
above command in combination with the @code{-frames:v} or @code{-t} option,
or in combination with -ss to start extracting from a certain point in time.

For creating a video from many images:
@example
ffmpeg -f image2 -framerate 12 -i foo-%03d.jpeg -s WxH foo.avi
@end example

The syntax @code{foo-%03d.jpeg} specifies to use a decimal number
composed of three digits padded with zeroes to express the sequence
number. It is the same syntax supported by the C printf function, but
only formats accepting a normal integer are suitable.

When importing an image sequence, -i also supports expanding
shell-like wildcard patterns (globbing) internally, by selecting the
image2-specific @code{-pattern_type glob} option.

For example, for creating a video from filenames matching the glob pattern
@code{foo-*.jpeg}:
@example
ffmpeg -f image2 -pattern_type glob -framerate 12 -i 'foo-*.jpeg' -s WxH foo.avi
@end example

@item
You can put many streams of the same type in the output:

@example
ffmpeg -i test1.avi -i test2.avi -map 1:1 -map 1:0 -map 0:1 -map 0:0 -c copy -y test12.nut
@end example

The resulting output file @file{test12.nut} will contain the first four streams
from the input files in reverse order.

@item
To force CBR video output:
@example
ffmpeg -i myfile.avi -b 4000k -minrate 4000k -maxrate 4000k -bufsize 1835k out.m2v
@end example

@item
The four options lmin, lmax, mblmin and mblmax use 'lambda' units,
but you may use the QP2LAMBDA constant to easily convert from 'q' units:
@example
ffmpeg -i src.ext -lmax 21*QP2LAMBDA dst.ext
@end example

@end itemize
@c man end EXAMPLES

@include config.texi
@ifset config-all
@ifset config-avutil
@include utils.texi
@end ifset
@ifset config-avcodec
@include codecs.texi
@include bitstream_filters.texi
@end ifset
@ifset config-avformat
@include formats.texi
@include protocols.texi
@end ifset
@ifset config-avdevice
@include devices.texi
@end ifset
@ifset config-swresample
@include resampler.texi
@end ifset
@ifset config-swscale
@include scaler.texi
@end ifset
@ifset config-avfilter
@include filters.texi
@end ifset
@end ifset

@chapter See Also

@ifhtml
@ifset config-all
@url{ffmpeg.html,ffmpeg}
@end ifset
@ifset config-not-all
@url{ffmpeg-all.html,ffmpeg-all},
@end ifset
@url{ffplay.html,ffplay}, @url{ffprobe.html,ffprobe},
@url{ffmpeg-utils.html,ffmpeg-utils},
@url{ffmpeg-scaler.html,ffmpeg-scaler},
@url{ffmpeg-resampler.html,ffmpeg-resampler},
@url{ffmpeg-codecs.html,ffmpeg-codecs},
@url{ffmpeg-bitstream-filters.html,ffmpeg-bitstream-filters},
@url{ffmpeg-formats.html,ffmpeg-formats},
@url{ffmpeg-devices.html,ffmpeg-devices},
@url{ffmpeg-protocols.html,ffmpeg-protocols},
@url{ffmpeg-filters.html,ffmpeg-filters}
@end ifhtml

@ifnothtml
@ifset config-all
ffmpeg(1),
@end ifset
@ifset config-not-all
ffmpeg-all(1),
@end ifset
ffplay(1), ffprobe(1),
ffmpeg-utils(1), ffmpeg-scaler(1), ffmpeg-resampler(1),
ffmpeg-codecs(1), ffmpeg-bitstream-filters(1), ffmpeg-formats(1),
ffmpeg-devices(1), ffmpeg-protocols(1), ffmpeg-filters(1)
@end ifnothtml

@include authors.texi

@ignore

@setfilename ffmpeg
@settitle ffmpeg video converter

@end ignore

@bye