ColorBars

ColorBars

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

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".

ColorBarsHD

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

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".

TV range

For both filters, in all color formats, luminance levels are TV range, where 0 IRE "black"=16
and 100 IRE "white"=235, within a total possible range of 0-255.

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

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		162	44	142		191	191	0		170	30	144
75% Cyan	16	180	180		131	156	44		0	191	191		134	161	30
75% Green	16	180	16		112	72	58		0	191	0		112	63	46
75% Magenta	180	16	180		84	184	198		191	0	191		79	193	210
75% Red	180	16	16		65	100	212		191	0	0		57	95	226
75% Bue	16	16	180		35	212	114		0	0	191		22	226	112

These colors are at "75%" of maximum, per common broadcast practice.
You may occasionally see "100%" color bars.^[1]

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.

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	168	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	182	152
0 IRE (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
0 IRE (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
0 IRE (Black)	16	16	16		16	128	128		0	0	0		0	128	128
(negative values will be clipped to 0)

"100% White" could also be called "100 IRE White."

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 the 16-235 range in two places: -I (where R=0) and the -4 bar.

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".