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)

TV range

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

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)  × 255/(235-16) // (for R, G, B, Y)

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

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

U_tv   = (U_full-128) × (240-16)/255 + 128 // (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	180	180	180		180	128	128		191	191	191		191	128	128
75% Yellow	180	180	16		168	44	136		191	191	0		177	32	137
75% Cyan	16	180	180		145	147	44		0	191	191		150	149	32
75% Green	16	180	16		134	63	52		0	191	0		137	54	41
75% Magenta	180	16	180		63	193	204		191	0	191		55	201	214
75% Red	180	16	16		51	109	212		191	0	0		41	106	223
75% Bue	16	16	180		28	212	120		0	0	191		14	223	118

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	0	58	98		16	158	95		-19	49	95		0	162	90
100% White	235	235	235		235	128	128		255	255	255		255	128	128
+Q	59	15	126		16	174	149		50	-1	128		0	180	151
Black	16	16	16		16	128	128		0	0	0		0	128	128
-4 IRE	7	7	7		7	128	128		-10	-10	-10		-10	128	128
Black	16	16	16		16	128	128		0	0	0		0	128	128
+4 IRE	25	25	25		25	128	128		10	10	10		10	128	128
Black	16	16	16		16	128	128		0	0	0		0	128	128
(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 (16-235) to full-range (0-255) 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 range in the -I and the -4 bars. These cannot be accurately converted to 0-255 range.

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

High bit depth

AVS+ For higher bit depths, the values given above are scaled appropriately – for example:

Color	8-bit	10-bit	16-bit
Super-black	0	0	0
Black	16	64	4096
U, V null	128	512	32768
White	235	940	60160
Super-white	255	1023	65535

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".