Commit 07851d79 authored by Stefano Sabatini's avatar Stefano Sabatini
Browse files

Add eval.texi file.

Originally committed as revision 25665 to svn://svn.ffmpeg.org/ffmpeg/trunk
parent 9fc2b708
......@@ -115,8 +115,8 @@ documentation: $(addprefix doc/, developer.html faq.html general.html libavfilte
$(HTMLPAGES) $(MANPAGES): doc/fftools-common-opts.texi
doc/ffmpeg.pod doc/ffmpeg-doc.html: doc/indevs.texi doc/filters.texi doc/outdevs.texi doc/protocols.texi
doc/ffplay.pod doc/ffplay-doc.html: doc/indevs.texi doc/filters.texi doc/outdevs.texi doc/protocols.texi
doc/ffmpeg.pod doc/ffmpeg-doc.html: doc/eval.texi doc/indevs.texi doc/filters.texi doc/outdevs.texi doc/protocols.texi
doc/ffplay.pod doc/ffplay-doc.html: doc/eval.texi doc/indevs.texi doc/filters.texi doc/outdevs.texi doc/protocols.texi
doc/ffprobe.pod doc/ffprobe-doc.html: doc/indevs.texi doc/protocols.texi
doc/%.html: TAG = HTML
......
@chapter Expression Evaluation
@c man begin EXPRESSION EVALUATION
When evaluating an arithemetic expression, FFmpeg uses an internal
formula evaluator, implemented through the @file{libavutil/eval.h}
interface.
An expression may contain unary, binary operators, constants, and
functions.
Two expressions @var{expr1} and @var{expr2} can be combined to form
another expression "@var{expr1};@var{expr2}".
@var{expr1} and @var{expr2} are evaluated in turn, and the new
expression evaluates to the value of @var{expr2}.
The following binary operators are available: @code{+}, @code{-},
@code{*}, @code{/}, @code{^}.
The following unary operators are available: @code{+}, @code{-}.
The following functions are available:
@table @option
@item sinh(x)
@item cosh(x)
@item tanh(x)
@item sin(x)
@item cos(x)
@item tan(x)
@item atan(x)
@item asin(x)
@item acos(x)
@item exp(x)
@item log(x)
@item abs(x)
@item squish(x)
@item gauss(x)
@item mod(x, y)
@item max(x, y)
@item min(x, y)
@item eq(x, y)
@item gte(x, y)
@item gt(x, y)
@item lte(x, y)
@item lt(x, y)
@item st(var, expr)
Allow to store the value of the expression @var{expr} in an internal
variable. @var{var} specifies the number of the variable where to
store the value, and it is a value ranging from 0 to 9. The function
returns the value stored in the internal variable.
@item ld(var)
Allow to load the value of the internal variable with number
@var{var}, which was previosly stored with st(@var{var}, @var{expr}).
The function returns the loaded value.
@item while(cond, expr)
Evaluate expression @var{expr} while the expression @var{cond} is
non-zero, and returns the value of the last @var{expr} evaluation, or
NAN if @var{cond} was always false.
@end table
Note that:
@code{*} works like AND
@code{+} works like OR
thus
@example
if A then B else C
@end example
is equivalent to
@example
A*B + not(A)*C
@end example
When A evaluates to either 1 or 0, that is the same as
@example
A*B + eq(A,0)*C
@end example
In your C code, you can extend the list of unary and binary functions,
and define recognized constants, so that they are available for your
expressions.
The evaluator also recognizes the International System number
postfixes. If 'i' is appended after the postfix, powers of 2 are used
instead of powers of 10. The 'B' postfix multiplies the value for 8,
and can be appended after another postfix or used alone. This allows
using for example 'KB', 'MiB', 'G' and 'B' as postfix.
Follows the list of available International System postfixes, with
indication of the corresponding powers of 10 and of 2.
@table @option
@item y
-24 / -80
@item z
-21 / -70
@item a
-18 / -60
@item f
-15 / -50
@item p
-12 / -40
@item n
-9 / -30
@item u
-6 / -20
@item m
-3 / -10
@item c
-2
@item d
-1
@item h
2
@item k
3 / 10
@item K
3 / 10
@item M
6 / 20
@item G
9 / 30
@item T
12 / 40
@item P
15 / 40
@item E
18 / 50
@item Z
21 / 60
@item Y
24 / 70
@end table
@c man end
......@@ -354,8 +354,39 @@ qp offset between P- and B-frames
@item -i_qoffset @var{offset}
qp offset between P- and I-frames
@item -rc_eq @var{equation}
Set rate control equation (@pxref{FFmpeg formula
evaluator}) (default = @code{tex^qComp}).
Set rate control equation (see section "Expression Evaluation")
(default = @code{tex^qComp}).
When computing the rate control equation expression, besides the
standard functions defined in the section "Expression Evaluation", the
following functions are available:
@table @var
@item bits2qp(bits)
@item qp2bits(qp)
@end table
and the following constants are available:
@table @var
@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
@item -rc_override @var{override}
rate control override for specific intervals
@item -me_method @var{method}
......@@ -694,74 +725,6 @@ 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 libx264} and use @code{-vpre max},
then it will search for the file @file{libx264-max.ffpreset}.
@anchor{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 statements are available: @code{ld}, @code{st},
@code{while}.
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 atan(x)
@item asin(x)
@item acos(x)
@item exp(x)
@item log(x)
@item abs(x)
@item squish(x)
@item gauss(x)
@item mod(x, y)
@item max(x, y)
@item min(x, y)
@item eq(x, y)
@item gte(x, y)
@item gt(x, y)
@item lte(x, y)
@item lt(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
@chapter Tips
......@@ -970,6 +933,7 @@ options have to be specified immediately after the name of the output
file to which you want to add them.
@c man end EXAMPLES
@include eval.texi
@include indevs.texi
@include outdevs.texi
@include protocols.texi
......
......@@ -153,6 +153,7 @@ Seek to percentage in file corresponding to fraction of width.
@c man end
@include eval.texi
@include indevs.texi
@include outdevs.texi
@include protocols.texi
......
Markdown is supported
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment