ColorBars

ColorBars

ColorBars ( [ int width, int height, string pixel_type ] )

ColorBars

ColorBars ( [ int width, int height, string pixel_type, bool staticframes ] ) AVS+

Produces a video clip containing SMPTE color bars (Rec. ITU-R BT.801-1) scaled to any image size.

By default, a 640×480, RGB32, TV range, 29.97 fps, 1 hour long clip is produced.

int  width = 640

int  height = 480

Set size of the returned clip.

string  pixel_type = "RGB32"

Set color format of the returned clip.

May be any of the following: "YUY2", "YV12", "YV24" (v2.60), or (default) "RGB32".

AVS+ "RGB32", "RGB64", "YUY2", or any planar RGB, 4:2:0 or 4:4:4 format.

bool  staticframes = true

AVS+ If set to false, generate all frames. Default true (one static frame is served)

ColorBarsHD

ColorBarsHD ( [ int width, int height, string pixel_type ] )
ColorBarsHD ( [ int width, int height, string pixel_type, bool staticframes ] ) AVS+

Added in v2.60, ColorBarsHD produces a video clip containing SMPTE color bars
(Rec. ITU-R BT.709 / arib std b28 v1.0) scaled to any image size.

By default, a 1288×720, YV24, TV range, 29.97 fps, 1 hour long clip is produced.

int  width = 1288

int  height = 720

Set size of the returned clip.

string  pixel_type = "YV24"

Set color format of the returned clip. Must be "YV24".

AVS+ "YV24" or other 4:4:4 format.

bool  staticframes = true

AVS+ If set to false, generate all frames. Default true (one static frame is served)

A note on notation

This page adopts the ITU style when discussing video levels which might be represented at different bit depths:

“ To avoid confusion between 8-bit and 10-bit representations, the eight most-significant bits are considered to be an integer part while the two additional bits, if present, are considered to be fractional part.

For example, the bit pattern 10010001 would be expressed as 145_d,
whereas the pattern 1001000101 would be expressed as 145.25_d.”

^{ITU-R BT.601-7 (page 4)}

Video levels shown below with the subscript "d" are assumed to be scaled by 2^(bit depth-8).
For example, 235_d at bit depth 10 becomes 235 × 2^(10-8) = 235 × 4 = 940.

see High bit-depth Support with Avisynth

see Avisynthplus color formats AVS+

TV range

For both filters, in all color formats, luminance levels are TV range, where black=16_d
and white=235_d, within a total possible range of 0-255_d.

The table below show the TV-range values ColorBarsHD generates, and those same values as they should be after converting to full range.

Y_full = (Y_tv-16_d)  × 255_d/(235_d-16_d) // (for R, G, B, Y)

U_full = (U_tv-128_d) × 255_d/(240_d-16_d) + 128_d // (for U, V)

Y_tv   = Y_full × (235_d-16_d)/255_d + 16_d // (for R, G, B, Y)

U_tv   = (U_full-128_d) × (240_d-16_d)/255_d + 128_d // (for U, V)

Color bar	TV range output								(expanded to full range)
	R	G	B		Y	U	V		R	G	B		Y	U	V
75% White	180d	180d	180d		180d	128d	128d		191d	191d	191d		191d	128d	128d
75% Yellow	180d	180d	16d		168d	44d	136d		191d	191d	0d		177d	32d	137d
75% Cyan	16d	180d	180d		145d	147d	44d		0d	191d	191d		150d	149d	32d
75% Green	16d	180d	16d		134d	63d	52d		0d	191d	0d		137d	54d	41d
75% Magenta	180d	16d	180d		63d	193d	204d		191d	0d	191d		55d	201d	214d
75% Red	180d	16d	16d		51d	109d	212d		191d	0d	0d		41d	106d	223d
75% Bue	16d	16d	180d		28d	212d	120d		0d	0d	191d		14d	223d	118d

These colors are at "75%" of maximum, per common broadcast practice. You may occasionally see "100%" color bars.^[1] They are rather useless, as you cannot detect gain or saturation that is too high on a signal that is already at maximum.

PLUGE

The lower part of the frame is called the PLUGE (also lowercase: "pluge") signal.
From left to right it consists of: -I, white, +Q, then a series of black and near-black bars: 0, -4, 0, +4 and 0 IRE relative to black.

Note 'IRE' is used here to mean 'percent luminance', on a scale from 0 (black) to 100 (white), ignoring the varying broadcast standards where black might be 0 IRE or 7.5 IRE depending on the country.

This section documents the ColorBars pluge only; ColorBarsHD's pluge is similar, but dispenses with -I and +Q

The table below show the TV-range values ColorBars generates, and those same values as they should be after converting to full range.

PLUGE Element	TV range output								(expanded to full range)
	R	G	B		Y	U	V		R	G	B		Y	U	V
-I	0d	58d	98d		16d	158d	95d		-19d	49d	95d		0d	162d	90d
100% White	235d	235d	235d		235d	128d	128d		255d	255d	255d		255d	128d	128d
+Q	59d	15d	126d		16d	174d	149d		50d	-1d	128d		0d	180d	151d
Black	16d	16d	16d		16d	128d	128d		0d	0d	0d		0d	128d	128d
-4 IRE	7d	7d	7d		7d	128d	128d		-10d	-10d	-10d		-10d	128d	128d
Black	16d	16d	16d		16d	128d	128d		0d	0d	0d		0d	128d	128d
+4 IRE	25d	25d	25d		25d	128d	128d		10d	10d	10d		10d	128d	128d
Black	16d	16d	16d		16d	128d	128d		0d	0d	0d		0d	128d	128d
(negative values will be clipped to 0)

The -I and +Q bars are vestigial artifacts of NTSC analog TV and are not really used any more.

The -4, 0 and +4 IRE bars can be used to set your monitor brightness – assuming your playback chain expands TV range (16_d-235_d) to full-range (0-255_d) as shown in the images above. The -4 IRE and 0 IRE bars should have the same apparent brightness (they should be as dark as the monitor can display), and the +4 should be a little brighter. If you can see the -4 bar, your monitor brightness is set too high; if you cannot see the +4 bar, your monitor brightness is set too low.^[2]

Note, the pluge signal goes out of 16-235_d range in the -I and the -4 bars. These cannot be accurately converted to 0-255_d range.

More information about the colorbars and the PLUGE can be found on the colorbars theory page.

Audio

For both filters, an audio tone is also generated. The tone is a 440Hz sine at 48KHz sample rate, 16 bit, stereo. The tone pulses in the right speaker, being turned on and off once every second. Level is 0 dBFS.

You can use Amplify to set a softer level (0dB can be a little deafening!)

ColorBarsHD
AmplifyDB(-20)

Broadcasting organizations usually specify an "alignment tone" accompanying colorbars at anywhere from -12 to -20 dBFS; if sending materials to another party, be sure to get their preferred alignment tone level. The exact level doesn't matter as long as all parties agree to it.

Miscellaneous

• Note, that for example

ColorBars(pixel_type="YUY2")

...is equivalent to

ColorBars(pixel_type="RGB32")
ConvertToYUY2(matrix="PC.601")  
# "PC.601" / "PC.709" don't scale the luma range

• When directly generating YUV format data, the color transitions are arranged to occur on a chroma-aligned boundary.

Changes

v2.60	Added pixel_type="YV24" to ColorBars. Initial release of ColorBarsHD.
v2.56	Added pixel_type="YUY2"/"YV12".