ffmpeg.texi

\input texinfo @c -*- texinfo -*-

@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_file}@} ... @{[@var{output_file_options}] @file{output_file}@} ...

@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 filename. Anything found on the command line 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). 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:

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

@end example

@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 again. 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:

@example
 _________                        __________              ______________
|         |                      |          |            |              |
| decoded |  simple filtergraph  | filtered |  encoder   | encoded data |
| frames  | -------------------> | frames   | ---------> | packets      |
|_________|                      |__________|            |______________|

@end example

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:

@example
 _______        _____________        _______        _____        ________
|       |      |             |      |       |      |     |      |        |
| input | ---> | deinterlace | ---> | scale | ---> | fps | ---> | output |
|_______|      |_____________|      |_______|      |_____|      |________|

@end example

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 e.g. 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:

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

@end example

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:

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

@end example

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 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 the stream with the most channels, for
subtitle it's the first subtitle stream. In the case where several streams of
the same type rate equally, the lowest numbered stream is chosen.

You can disable some of those defaults by using @code{-vn/-an/-sn} 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 avtools-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{filename} (@emph{input})
input file name

@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 -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{output})
Stop writing the output after its duration reaches @var{duration}.
@var{duration} may be a number in seconds, or in @code{hh:mm:ss[.xxx]} form.

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

@item -to @var{position} (@emph{output})
Stop writing the output at @var{position}.
@var{position} may be a number in seconds, or in @code{hh:mm:ss[.xxx]} form.

-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.

@item -ss @var{position} (@emph{input/output})
When used as an input option (before @code{-i}), seeks in this input file to
@var{position}. When used as an output option (before an output filename),
decodes but discards input until the timestamps reach @var{position}. This is
slower, but more accurate.

@var{position} may be either in seconds or in @code{hh:mm:ss[.xxx]} form.

@item -itsoffset @var{offset} (@emph{input})
Set the input time offset in seconds.
@code{[-]hh:mm:ss[.xxx]} syntax is also supported.
The offset is added to the timestamps of the input files.
Specifying a positive offset means that the corresponding
streams are delayed by @var{offset} seconds.

@item -timestamp @var{time} (@emph{output})
Set the recording timestamp in the container.
The syntax for @var{time} is:
@example
now|([(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((HH:MM:SS[.m...])|(HHMMSS[.m...]))[Z|z])
@end example
If the value is "now" it takes the current time.
Time is local time unless 'Z' or 'z' is appended, in which case it is
interpreted as UTC.
If the year-month-day part is not specified it takes the current
year-month-day.

@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 or chapters. 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:1 language=eng OUTPUT
@end example

@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 -dframes @var{number} (@emph{output})
Set the number of data frames to record. This is an alias for @code{-frames:d}.

@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} is
codec-dependent.

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

@var{filter_graph} is a description of the filter graph to apply to
the stream, and must have a single input and a single output of the
same type of the stream. In the filter graph, 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 filter graphs 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 -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".

@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.

@end table

@section Video Options

@table @option
@item -vframes @var{number} (@emph{output})
Set the number of video frames to record. This is an alias for @code{-frames:v}.
@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}.

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.

@item -vn (@emph{output})
Disable video recording.

@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 -vlang @var{code}
Set the ISO 639 language code (3 letters) of the current video stream.

@item -vf @var{filter_graph} (@emph{output})
Create the filter graph specified by @var{filter_graph} 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 filter graphs 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 -deinterlace
Deinterlace pictures.
This option is deprecated since the deinterlacing is very low quality.
Use the yadif filter with @code{-filter:v yadif}.
@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 -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.
@end table

@section Audio Options

@table @option
@item -aframes @var{number} (@emph{output})
Set the number of audio frames to record. This is an alias for @code{-frames:a}.
@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.
@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{filter_graph} (@emph{output})
Create the filter graph specified by @var{filter_graph} 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 -slang @var{code}
Set the ISO 639 language code (3 letters) of the current subtitle stream.
@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.
@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.

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

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

@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.

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

@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.
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). If
your input(s) is coming from some other live streaming source (through HTTP or
UDP for example) the server might already be in real-time, thus the option will
likely not be required. On the other hand, this is meaningful if your input(s)
is a file you are trying to push in real-time.
@item -loop_input
Loop over the input stream. Currently it works only for image
streams. This option is used for automatic FFserver testing.
This option is deprecated, use -loop 1.
@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 -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 -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 -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 infile -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{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 ';'