Raffriff42: add "bit depth equivalent color value" table

2018-01-15T15:50:32Z

add "bit depth equivalent color value" table

Raffriff42: describe autoscaling, show helper scripts

2017-05-29T05:24:47Z

describe autoscaling, show helper scripts

New page

<div style="max-width:82em; min-width:42em; text-align:right" >
{{AvsPlusFilter}}
</div>
<div style="max-width:62em; min-width:42em;" >
'''''Autoscale''''' is the term being used to describe [[Grammar#Functions.2C_Filters_and_Arguments|filter and function arguments]] that adjust themselves to the current bit depth – the [[Clip_properties#Color_Format|BitsPerComponent]] of the main source clip. A related concept is [[D_Notation|'d' notation]]: 16{{Template:D}}-235{{Template:D}} refers to normal [[Luminance_levels#What_are_luminance_levels.3F|TV-range levels]] at any bit depth.

==== Examples ====
To see a filter with ''non''-autoscaling arguments, consider '''[[Levels]]''':
<div {{BoxWidthIndent|42|2}} >
Levels(clip C,
\ int {{BoldColor|blue|100|input_low}}, float gamma, {{BoldColor|blue|100|int input_high}},
\ int {{BoldColor|blue|100|output_low}}, int {{BoldColor|blue|100|output_high}} [,
\ bool coring, bool dither])
</div>
All the arguments in blue expect user inputs in the normal 0-255 range – assuming 8-bit video. For 10-bit, the input range is 0-1023, and for 16-bit, it's 0-65535. Scripts that specify 8-bit '''Levels''' arguments need to be altered for use with other bit depths. For those used to "thinking in 8-bit," writing scripts for multiple bit depths can be cumbersome.

That's not to say [[Levels]] is wrong or buggy – what it does makes sense: it is the humans that need to adjust. There are utility functions to help with this, which will be discussed below.

Another example is '''[[RGBAdjust]]''' with its ''bias'' arguments: {{FuncArg|rb}}=16 always lifts the Red channel by 16 units, whether on the 0-255 or the 0-65535 scale. It does what you ''say'', not necessarily what you mean.

To see a filter '''with''' autoscaling arguments, consider '''[[ColorYUV]]''':
<div {{BoxWidthIndent|42|2}} >
ColorYUV(clip [,
\ float gain_y, float {{BoldColor|blue|100|off_y}}, float gamma_y, float cont_y,
\ float gain_u, float {{BoldColor|blue|100|off_u}}, float gamma_u, float cont_u,
\ float gain_v, float {{BoldColor|blue|100|off_v}}, float gamma_v, float cont_v,
\ string levels, string opt, bool showyuv, bool analyze,
\ bool autowhite, bool autogain, bool conditional ] ))
</div>
The {{FuncArg|off_''x''}} arguments (in blue) add or subtract a given amount from all pixels in the given color channel, and the amount is always on the 0-255 scale – that is, {{FuncArg|off_y}}=255 will always turn black to white, at any bit depth.

In 8-bit video, setting {{FuncArg|off_y}}=16 will raise all luminance values by 16 units on the 0-255 scale – but in 10-bit video, {{FuncArg|off_y}}=16 will raise all luminance values by '''''64''''' units on the 0-1023 scale.

The argument value has been adjusted by the filter to give the same ''visual effect.'' '''That's autoscaling.'''

==== User-Defined Autoscaling functions ====
For filters and function that don't autoscale, there are some helper functions you can call upon, which are included in raffriff42's [[User:Raffriff42/Utils-r41_Quick_Reference|''Utils-r41.avsi'']] script. These three are the ones most important for autoscaling:
:{{FuncDef|sc8f(clip T, float f, [bool ''cx''])}}
:: Scale an 8-bit value for target clip {{FuncArg|T}}

:{{FuncDef|sc8x(clip T, float f)}}
:: Scale an 8-bit value for target clip {{FuncArg|T}}; clamp output

:{{FuncDef|sc8s(clip T, float f, [int ''decimals''])}}
:: Scale an 8-bit value for target clip {{FuncArg|T}}; string result

You can use them to make '''Levels''' autoscale, so that the old 8-bit arguments give the same visual result in any bit depth:
<div {{BoxWidthIndent|56|2}} >
function LevelsPlus(clip C,
\ int input_low, float gamma, int input_high,
\ int output_low, int output_high,
\ bool "coring", bool "dither")
{
return C.[[Levels]](
\ C.{{BoldColor|blue|100|sc8x}}(input_low),
\ gamma,
\ C.{{BoldColor|blue|100|sc8x}}(input_high),
\ C.{{BoldColor|blue|100|sc8x}}(output_low),
\ C.{{BoldColor|blue|100|sc8x}}(output_high),
\ coring, dither)
}
</div>
[[User:Raffriff42/Utils-r41_Quick_Reference#LevelsPlus|LevelsPlus]] is included in the script previously mentioned.

You don't have to write wrapper scripts like the one above; you can insert them only where needed:
<div {{BoxWidthIndent|56|2}} >
[[RGBAdjust]](rb={{BoldColor|blue|100|sc8f}}(8), gb={{BoldColor|blue|100|sc8f}}(-8), bb={{BoldColor|blue|100|sc8f}}(12))

[[Limiter]](min_chroma={{BoldColor|blue|100|sc8x}}(128-64), max_chroma={{BoldColor|blue|100|sc8x}}(128+64))
</div>
These statements will have the same visual effect at all bit depths.

</div>

[[Category:Avisynthplus]]

← Older revision		Revision as of 15:50, 15 January 2018
Line 4:		Line 4:
	<div style="max-width:62em; min-width:42em;" >		<div style="max-width:62em; min-width:42em;" >
	'''''Autoscale''''' is the term being used to describe [[Grammar#Functions.2C_Filters_and_Arguments\|filter and function arguments]] that adjust themselves to the current bit depth – the [[Clip_properties#Color_Format\|BitsPerComponent]] of the main source clip. A related concept is [[D_Notation\|'d' notation]]: 16{{Template:D}}-235{{Template:D}} refers to normal [[Luminance_levels#What_are_luminance_levels.3F\|TV-range levels]] at any bit depth.		'''''Autoscale''''' is the term being used to describe [[Grammar#Functions.2C_Filters_and_Arguments\|filter and function arguments]] that adjust themselves to the current bit depth – the [[Clip_properties#Color_Format\|BitsPerComponent]] of the main source clip. A related concept is [[D_Notation\|'d' notation]]: 16{{Template:D}}-235{{Template:D}} refers to normal [[Luminance_levels#What_are_luminance_levels.3F\|TV-range levels]] at any bit depth.
		+	:{\| class="wikitable"
		+	\|-
		+	\|colspan="6" \|bit depth equivalent color values
		+	\|-
		+	!style="text-align:right"\|8
		+	\|style="text-align:right"\|0
		+	\|style="text-align:right"\|16
		+	\|style="text-align:right"\|128
		+	\|style="text-align:right"\|235
		+	\|style="text-align:right"\|255
		+	\|-
		+	!10
		+	\|style="text-align:right"\|0
		+	\|style="text-align:right"\|64
		+	\|style="text-align:right"\|512
		+	\|style="text-align:right"\|940
		+	\|style="text-align:right"\|1020
		+	\|-
		+	!12
		+	\|style="text-align:right"\|0
		+	\|style="text-align:right"\|256
		+	\|style="text-align:right"\|2048
		+	\|style="text-align:right"\|3670
		+	\|style="text-align:right"\|4080
		+	\|-
		+	!14
		+	\|style="text-align:right"\|0
		+	\|style="text-align:right"\|1024
		+	\|style="text-align:right"\|8192
		+	\|style="text-align:right"\|15040
		+	\|style="text-align:right"\|16320
		+	\|-
		+	!16
		+	\|style="text-align:right"\|0
		+	\|style="text-align:right"\|4096
		+	\|style="text-align:right"\|32768
		+	\|style="text-align:right"\|60160
		+	\|style="text-align:right"\|65280
		+	\|-
		+	!32
		+	\|style="text-align:right"\|0.0
		+	\|style="text-align:right"\|<sup>16</sup>/<sub>256</sub>
		+	\|style="text-align:right"\|<sup>128</sup>/<sub>256</sub>
		+	\|style="text-align:right"\|<sup>235</sup>/<sub>256</sub>
		+	\|style="text-align:right"\|<sup>255</sup>/<sub>256</sub>
		+	\|}

Autoscale parameter - Revision history

Raffriff42: add "bit depth equivalent color value" table

Raffriff42: describe autoscaling, show helper scripts