doc/filters: correct luma terminology

Partially fixes #10427

See https://poynton.ca/notes/colour_and_gamma/ColorFAQ.html#RTFToC11 for
ref.

doc/filters.texi

@@ -8482,10 +8482,10 @@ This filter supports the all above options as @ref{commands}.
 @section bbox
 
 Compute the bounding box for the non-black pixels in the input frame
-luminance plane.
+luma plane.
 
 This filter computes the bounding box containing all the pixels with a
-luminance value greater than the minimum allowed value.
+luma value greater than the minimum allowed value.
 The parameters describing the bounding box are printed on the filter
 log.
 
@@ -8493,7 +8493,7 @@ The filter accepts the following option:
 
 @table @option
 @item min_val
-Set the minimal luminance value. Default is @code{16}.
+Set the minimal luma value. Default is @code{16}.
 @end table
 
 @subsection Commands
@@ -8616,14 +8616,14 @@ Default value is 0.98.
 @item pixel_black_th, pix_th
 Set the threshold for considering a pixel "black".
 
-The threshold expresses the maximum pixel luminance value for which a
+The threshold expresses the maximum pixel luma value for which a
 pixel is considered "black". The provided value is scaled according to
 the following equation:
 @example
-@var{absolute_threshold} = @var{luminance_minimum_value} + @var{pixel_black_th} * @var{luminance_range_size}
+@var{absolute_threshold} = @var{luma_minimum_value} + @var{pixel_black_th} * @var{luma_range_size}
 @end example
 
-@var{luminance_range_size} and @var{luminance_minimum_value} depend on
+@var{luma_range_size} and @var{luma_minimum_value} depend on
 the input video format, the range is [0-255] for YUV full-range
 formats and [16-235] for YUV non full-range formats.
 
@@ -14613,7 +14613,7 @@ The filter accepts the following options:
 
 @table @option
 @item lum_expr, lum
-Set the luminance expression.
+Set the luma expression.
 @item cb_expr, cb
 Set the chrominance blue expression.
 @item cr_expr, cr
@@ -14638,7 +14638,7 @@ colorspace.
 If one of the chrominance expression is not defined, it falls back on the other
 one. If no alpha expression is specified it will evaluate to opaque value.
 If none of chrominance expressions are specified, they will evaluate
-to the luminance expression.
+to the luma expression.
 
 The expressions can use the following variables and functions:
 
@@ -14669,7 +14669,7 @@ Return the value of the pixel at location (@var{x},@var{y}) of the current
 plane.
 
 @item lum(x, y)
-Return the value of the pixel at location (@var{x},@var{y}) of the luminance
+Return the value of the pixel at location (@var{x},@var{y}) of the luma
 plane.
 
 @item cb(x, y)
@@ -17129,7 +17129,7 @@ set blue component expression
 alpha component expression
 
 @item y
-set Y/luminance component expression
+set Y/luma component expression
 @item u
 set U/Cb component expression
 @item v
@@ -17204,7 +17204,7 @@ lutyuv="y=negval:u=negval:v=negval"
 @end example
 
 @item
-Negate luminance:
+Negate luma:
 @example
 lutyuv=y=negval
 @end example
@@ -17234,7 +17234,7 @@ format=rgba,lutrgb=a="maxval-minval/2"
 @end example
 
 @item
-Correct luminance gamma by a factor of 0.5:
+Correct luma gamma by a factor of 0.5:
 @example
 lutyuv=y=gammaval(0.5)
 @end example
@@ -19443,10 +19443,10 @@ Honor the quality commands for this subfilter.
 Do chrominance filtering, too (default).
 
 @item y/nochrom
-Do luminance filtering only (no chrominance).
+Do luma filtering only (no chrominance).
 
 @item n/noluma
-Do chrominance filtering only (no luminance).
+Do chrominance filtering only (no luma).
 @end table
 
 These options can be appended after the subfilter name, separated by a '|'.
@@ -19518,7 +19518,7 @@ larger -> stronger filtering
 @item al/autolevels[:f/fullyrange], automatic brightness / contrast correction
 @table @option
 @item f/fullyrange
-Stretch luminance to @code{0-255}.
+Stretch luma to @code{0-255}.
 @end table
 
 @item lb/linblenddeint
@@ -19586,7 +19586,7 @@ pp=default/tmpnoise|1|2|3
 @end example
 
 @item
-Apply deblocking on luminance only, and switch vertical deblocking on or off
+Apply deblocking on luma only, and switch vertical deblocking on or off
 automatically depending on available CPU time:
 @example
 pp=hb|y/vb|a
@@ -25032,7 +25032,7 @@ This filter supports same @ref{commands} as options.
 @section waveform
 Video waveform monitor.
 
-The waveform monitor plots color component intensity. By default luminance
+The waveform monitor plots color component intensity. By default luma
 only. Each column of the waveform corresponds to a column of pixels in the
 source video.
 
@@ -25087,7 +25087,7 @@ correction is easy to perform by making level adjustments the three waveforms.
 Default is @code{stack}.
 
 @item components, c
-Set which color components to display. Default is 1, which means only luminance
+Set which color components to display. Default is 1, which means only luma
 or red color component if input is in RGB colorspace. If is set for example to
 7 it will display all 3 (if) available color components.
 
@@ -28589,7 +28589,7 @@ color=c=red@@0.2:s=qcif:r=10
 
 @item
 If the input content is to be ignored, @code{nullsrc} can be used. The
-following command generates noise in the luminance plane by employing
+following command generates noise in the luma plane by employing
 the @code{geq} filter:
 @example
 nullsrc=s=256x256, geq=random(1)*255:128:128