ffmpeg-doc.texi

ffmpeg源码分析

Set DCT algorithm to @var{algo}. Available values are:
@table @samp
@item 0
FF_DCT_AUTO (default)
@item 1
FF_DCT_FASTINT
@item 2
FF_DCT_INT
@item 3
FF_DCT_MMX
@item 4
FF_DCT_MLIB
@item 5
FF_DCT_ALTIVEC
@end table

@item -idct_algo algo
Set IDCT algorithm to @var{algo}. Available values are:
@table @samp
@item 0
FF_IDCT_AUTO (default)
@item 1
FF_IDCT_INT
@item 2
FF_IDCT_SIMPLE
@item 3
FF_IDCT_SIMPLEMMX
@item 4
FF_IDCT_LIBMPEG2MMX
@item 5
FF_IDCT_PS2
@item 6
FF_IDCT_MLIB
@item 7
FF_IDCT_ARM
@item 8
FF_IDCT_ALTIVEC
@item 9
FF_IDCT_SH4
@item 10
FF_IDCT_SIMPLEARM
@end table

@item -er n
Set error resilience to @var{n}.
@table @samp
@item 1
FF_ER_CAREFUL (default)
@item 2
FF_ER_COMPLIANT
@item 3
FF_ER_AGGRESSIVE
@item 4
FF_ER_VERY_AGGRESSIVE
@end table

@item -ec bit_mask
Set error concealment to @var{bit_mask}. @var{bit_mask} is a bit mask of
the following values:
@table @samp
@item 1
FF_EC_GUESS_MVS (default = enabled)
@item 2
FF_EC_DEBLOCK (default = enabled)
@end table

@item -bf frames
Use 'frames' B-frames (supported for MPEG-1, MPEG-2 and MPEG-4).
@item -mbd mode
macroblock decision
@table @samp
@item 0
FF_MB_DECISION_SIMPLE: Use mb_cmp (cannot change it yet in FFmpeg).
@item 1
FF_MB_DECISION_BITS: Choose the one which needs the fewest bits.
@item 2
FF_MB_DECISION_RD: rate distortion
@end table

@item -4mv
Use four motion vector by macroblock (MPEG-4 only).
@item -part
Use data partitioning (MPEG-4 only).
@item -bug param
Work around encoder bugs that are not auto-detected.
@item -strict strictness
How strictly to follow the standards.
@item -aic
Enable Advanced intra coding (h263+).
@item -umv
Enable Unlimited Motion Vector (h263+)

@item -deinterlace
Deinterlace pictures.
@item -interlace
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 -vhook module
Insert video processing @var{module}. @var{module} contains the module
name and its parameters separated by spaces.
@end table

@section Audio Options

@table @option
@item -ar freq
Set the audio sampling frequency (default = 44100 Hz).
@item -ab bitrate
Set the audio bitrate in kbit/s (default = 64).
@item -ac channels
Set the number of audio channels (default = 1).
@item -an
Disable audio recording.
@item -acodec codec
Force audio codec to @var{codec}. Use the @code{copy} special value to
specify that the raw codec data must be copied as is.
@end table

@section Audio/Video grab options

@table @option
@item -vd device
sEt video grab device (e.g. @file{/dev/video0}).
@item -vc channel
Set video grab channel (DV1394 only).
@item -tvstd standard
Set television standard (NTSC, PAL (SECAM)).
@item -dv1394
Set DV1394 grab.
@item -ad device
Set audio device (e.g. @file{/dev/dsp}).
@end table

@section Advanced options

@table @option
@item -map file:stream
Set input stream mapping.
@item -debug
Print specific debug info.
@item -benchmark
Add timings for benchmarking.
@item -hex
Dump each input packet.
@item -bitexact
Only use bit exact algorithms (for codec testing).
@item -ps size
Set packet size in bits.
@item -re
Read input at native frame rate. Mainly used to simulate a grab device.
@item -loop
Loop over the input stream. Currently it works only for image
streams. This option is used for automatic FFserver testing.
@item -loop_output number_of_times
Repeatedly loop output for formats that support looping such as animated GIF
(0 will loop the output infinitely).
@end table

@node FFmpeg formula evaluator
@section FFmpeg formula evaluator

When evaluating a rate control string, FFmpeg uses an internal formula
evaluator.

The following binary operators are available: @code{+}, @code{-},
@code{*}, @code{/}, @code{^}.

The following unary operators are available: @code{+}, @code{-},
@code{(...)}.

The following functions are available:
@table @var
@item sinh(x)
@item cosh(x)
@item tanh(x)
@item sin(x)
@item cos(x)
@item tan(x)
@item exp(x)
@item log(x)
@item squish(x)
@item gauss(x)
@item abs(x)
@item max(x, y)
@item min(x, y)
@item gt(x, y)
@item lt(x, y)
@item eq(x, y)
@item bits2qp(bits)
@item qp2bits(qp)
@end table

The following constants are available:
@table @var
@item PI
@item E
@item iTex
@item pTex
@item tex
@item mv
@item fCode
@item iCount
@item mcVar
@item var
@item isI
@item isP
@item isB
@item avgQP
@item qComp
@item avgIITex
@item avgPITex
@item avgPPTex
@item avgBPTex
@item avgTex
@end table

@c man end

@ignore

@setfilename ffmpeg
@settitle FFmpeg video converter

@c man begin SEEALSO
ffserver(1), ffplay(1) and the HTML documentation of @file{ffmpeg}.
@c man end

@c man begin AUTHOR
Fabrice Bellard
@c man end

@end ignore

@section Protocols

The filename can be @file{-} to read from standard input or to write
to standard output.

FFmpeg also handles many protocols specified with an URL syntax.

Use 'ffmpeg -formats' to see a list of the supported protocols.

The protocol @code{http:} is currently used only to communicate with
FFserver (see the FFserver documentation). When FFmpeg will be a
video player it will also be used for streaming :-)

@chapter 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 50 -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 '-intra' 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 kHz for MPEG audio, 22050 or 11025 for AC3).

@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).

@item When converting video files, you can use the '-sameq' option which
uses the same quality factor in the encoder as in the decoder.
It allows almost lossless encoding.

@end itemize

@chapter Supported File Formats and Codecs

You can use the @code{-formats} option to have an exhaustive list.

@section File Formats

FFmpeg supports the following file formats through the @code{libavformat}
library:

@multitable @columnfractions .4 .1 .1 .4
@item Supported File Format @tab Encoding @tab Decoding @tab Comments
@item MPEG audio @tab X @tab X
@item MPEG-1 systems @tab X  @tab  X
@tab muxed audio and video
@item MPEG-2 PS @tab X  @tab  X
@tab also known as @code{VOB} file
@item MPEG-2 TS @tab    @tab  X
@tab also known as DVB Transport Stream
@item ASF@tab X @tab X
@item AVI@tab X @tab X
@item WAV@tab X @tab X
@item Macromedia Flash@tab X @tab X
@tab Only embedded audio is decoded.
@item FLV              @tab  X @tab X
@tab Macromedia Flash video files
@item Real Audio and Video @tab X @tab X
@item Raw AC3 @tab X  @tab  X
@item Raw MJPEG @tab X  @tab  X
@item Raw MPEG video @tab X  @tab  X
@item Raw PCM8/16 bits, mulaw/Alaw@tab X  @tab  X
@item Raw CRI ADX audio @tab X  @tab  X
@item Raw Shorten audio @tab    @tab  X
@item SUN AU format @tab X  @tab  X
@item NUT @tab X @tab X @tab NUT Open Container Format
@item QuickTime        @tab X @tab  X
@item MPEG-4           @tab X @tab  X
@tab MPEG-4 is a variant of QuickTime.
@item Raw MPEG4 video  @tab  X @tab  X
@item DV               @tab  X @tab  X
@item 4xm              @tab    @tab X
@tab 4X Technologies format, used in some games.
@item Playstation STR  @tab    @tab X
@item Id RoQ           @tab    @tab X
@tab Used in Quake III, Jedi Knight 2, other computer games.
@item Interplay MVE    @tab    @tab X
@tab Format used in various Interplay computer games.
@item WC3 Movie        @tab    @tab X
@tab Multimedia format used in Origin's Wing Commander III computer game.
@item Sega FILM/CPK    @tab    @tab X
@tab Used in many Sega Saturn console games.
@item Westwood Studios VQA/AUD  @tab    @tab X
@tab Multimedia formats used in Westwood Studios games.