diff --git a/Makefile b/Makefile
index b81b65567d..e9d98545a7 100644
--- a/Makefile
+++ b/Makefile
@@ -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
diff --git a/doc/eval.texi b/doc/eval.texi
new file mode 100644
index 0000000000..c26893d1bd
--- /dev/null
+++ b/doc/eval.texi
@@ -0,0 +1,137 @@
+@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
diff --git a/doc/ffmpeg-doc.texi b/doc/ffmpeg-doc.texi
index eb7c8fdd80..4d707ea567 100644
--- a/doc/ffmpeg-doc.texi
+++ b/doc/ffmpeg-doc.texi
@@ -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
diff --git a/doc/ffplay-doc.texi b/doc/ffplay-doc.texi
index d761f13a3b..07c887565f 100644
--- a/doc/ffplay-doc.texi
+++ b/doc/ffplay-doc.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