ffmpeg-doc.texi

arm平台下的H264编码和解码源代码

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_CAREFULL (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: chooses the one which needs the fewest bits
@item 2
FF_MB_DECISION_RD: rate distoration
@end table

@item -4mv
use four motion vector by macroblock (only MPEG-4)
@item -part
use data partitioning (only MPEG-4)
@item -bug param
workaround not auto detected encoder bugs
@item -strict strictness
how strictly to follow the standarts
@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 (only MPEG-2 and MPEG-4). Use this option
if your input file is interlaced and if you want to keep the interlaced
format for minimum losses. The alternative is to deinterlace the input
stream with @option{-deinterlace}, but deinterlacing introduces more
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 -ab bitrate         
set audio bitrate (in kbit/s)
@item -ar freq    
set the audio sampling freq (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
tell 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 ffserver automatic testing.
@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 the standard input or to write
to the standard output.

ffmpeg handles also many protocols specified with the URL syntax.

Use 'ffmpeg -formats' to have 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 bit rate application, use a low frame rate
and a small gop size. This is especially true for real video 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 of 1 indicates that a very good quality could
be achieved. The value of 31 indicates the worst quality. If q=31
too often, it means that the encoder cannot compress enough to meet
your bit rate. You must either increase the bit rate, 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
completely motion estimation (you have only I frames, which means it
is about as good as JPEG compression).

@item To have very low bitrates in audio, 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 in the encoder the same quality factor than in the decoder. It
allows to be almost lossless in 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
@item Supported File Format @tab Encoding @tab Decoding @tab Comments
@item MPEG audio @tab X @tab X
@item MPEG1 systems @tab X  @tab  X 
@tab muxed audio and video
@item MPEG2 PS @tab X  @tab  X 
@tab also known as @code{VOB} file
@item MPEG2 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 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 MPEG4            @tab X @tab  X 
@tab MPEG4 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
@item Id Cinematic (.cin) @tab    @tab X
@tab Used in Quake II
@item FLIC format      @tab    @tab X
@tab .fli/.flc files
@item Sierra VMD       @tab    @tab X
@tab used in Sierra CD-ROM games
@item Matroska         @tab    @tab X
@end multitable

@code{X} means that the encoding (resp. decoding) is supported.

@section Image Formats

FFmpeg can read and write images for each frame of a video sequence. The
following image formats are supported:

@multitable @columnfractions .4 .1 .1
@item Supported Image Format @tab Encoding @tab Decoding @tab Comments
@item PGM, PPM     @tab X @tab X