ffmpeg.texi

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}.
@c man end OPTIONS

@chapter Tips
@c man begin TIPS

@itemize
@item
For streaming at very low bitrate application, use a low frame rate
and a small GOP size. This is especially true for RealVideo where
the Linux player does not seem to be very fast, so it can miss
frames. An example is:

@example
ffmpeg -g 3 -r 3 -t 10 -b:v 50k -s qcif -f rv10 /tmp/b.rm
@end example

@item
The parameter 'q' which is displayed while encoding is the current
quantizer. The value 1 indicates that a very good quality could
be achieved. The value 31 indicates the worst quality. If q=31 appears
too often, it means that the encoder cannot compress enough to meet
your bitrate. You must either increase the bitrate, decrease the
frame rate or decrease the frame size.

@item
If your computer is not fast enough, you can speed up the
compression at the expense of the compression ratio. You can use
'-me zero' to speed up motion estimation, and '-g 0' to disable
motion estimation completely (you have only I-frames, which means it
is about as good as JPEG compression).

@item
To have very low audio bitrates, reduce the sampling frequency
(down to 22050 Hz for MPEG audio, 22050 or 11025 for AC-3).

@item
To have a constant quality (but a variable bitrate), use the option
'-qscale n' when 'n' is between 1 (excellent quality) and 31 (worst
quality).

@end itemize
@c man end TIPS

@chapter Examples
@c man begin EXAMPLES

@section Preset files

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

Preset files are specified with the @code{pre} option, this option takes a
preset name as input.  FFmpeg searches for a file named @var{preset_name}.avpreset in
the directories @file{$AVCONV_DATADIR} (if set), and @file{$HOME/.ffmpeg}, and in
the data directory defined at configuration time (usually @file{$PREFIX/share/ffmpeg})
in that order.  For example, if the argument is @code{libx264-max}, it will
search for the file @file{libx264-max.avpreset}.

@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 -s cif -r 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 -s cif -r 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 -formats}.

@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 -vframes or -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 -i foo-%03d.jpeg -r 12 -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. To lower the chance of interfering
with your actual file names and the shell's glob expansion, you are required
to activate glob meta characters by prefixing them with a single @code{%}
character, like in @code{foo-%*.jpeg}, @code{foo-%?%?%?.jpeg} or
@code{foo-00%[234%]%*.jpeg}.
If your filename actually contains a character sequence of a @code{%} character
followed by a glob character, you must double the @code{%} character to escape
it. Imagine your files begin with @code{%?-foo-}, then you could use a glob
pattern like @code{%%?-foo-%*.jpeg}. For input patterns that could be both a
printf or a glob pattern, ffmpeg will assume it is a glob pattern.

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

@example
ffmpeg -i test1.avi -i test2.avi -map 0.3 -map 0.2 -map 0.1 -map 0.0 -c copy test12.nut
@end example

The resulting output file @file{test12.avi} will contain first four streams from
the input file 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 syntax.texi
@include eval.texi
@include decoders.texi
@include encoders.texi
@include demuxers.texi
@include muxers.texi
@include indevs.texi
@include outdevs.texi
@include protocols.texi
@include bitstream_filters.texi
@include filters.texi
@include metadata.texi

@ignore

@setfilename ffmpeg
@settitle ffmpeg video converter

@c man begin SEEALSO
ffplay(1), ffprobe(1), ffserver(1) and the FFmpeg HTML documentation
@c man end

@c man begin AUTHORS
See git history
@c man end

@end ignore

@bye