2.9.1. Packed RGB formats

2.9.1.1. Description

These formats are designed to match the pixel formats of typical PC graphics frame buffers. They occupy 8, 16, 24 or 32 bits per pixel. These are all packed-pixel formats, meaning all the data for a pixel lie next to each other in memory.

Packed RGB Image Formats

Identifier	Code		Byte 0 in memory									Byte 1									Byte 2									Byte 3
		Bit	7	6	5	4	3	2	1	0		7	6	5	4	3	2	1	0		7	6	5	4	3	2	1	0		7	6	5	4	3	2	1	0
V4L2_PIX_FMT_RGB332	‘RGB1’		r2	r1	r0	g2	g1	g0	b1	b0
V4L2_PIX_FMT_ARGB444	‘AR12’		g3	g2	g1	g0	b3	b2	b1	b0		a3	a2	a1	a0	r3	r2	r1	r0
V4L2_PIX_FMT_XRGB444	‘XR12’		g3	g2	g1	g0	b3	b2	b1	b0						r3	r2	r1	r0
V4L2_PIX_FMT_ARGB555	‘AR15’		g2	g1	g0	b4	b3	b2	b1	b0		a	r4	r3	r2	r1	r0	g4	g3
V4L2_PIX_FMT_XRGB555	‘XR15’		g2	g1	g0	b4	b3	b2	b1	b0			r4	r3	r2	r1	r0	g4	g3
V4L2_PIX_FMT_RGB565	‘RGBP’		g2	g1	g0	b4	b3	b2	b1	b0		r4	r3	r2	r1	r0	g5	g4	g3
V4L2_PIX_FMT_ARGB555X	‘AR15’ | (1 << 31)		a	r4	r3	r2	r1	r0	g4	g3		g2	g1	g0	b4	b3	b2	b1	b0
V4L2_PIX_FMT_XRGB555X	‘XR15’ | (1 << 31)			r4	r3	r2	r1	r0	g4	g3		g2	g1	g0	b4	b3	b2	b1	b0
V4L2_PIX_FMT_RGB565X	‘RGBR’		r4	r3	r2	r1	r0	g5	g4	g3		g2	g1	g0	b4	b3	b2	b1	b0
V4L2_PIX_FMT_BGR24	‘BGR3’		b7	b6	b5	b4	b3	b2	b1	b0		g7	g6	g5	g4	g3	g2	g1	g0		r7	r6	r5	r4	r3	r2	r1	r0
V4L2_PIX_FMT_RGB24	‘RGB3’		r7	r6	r5	r4	r3	r2	r1	r0		g7	g6	g5	g4	g3	g2	g1	g0		b7	b6	b5	b4	b3	b2	b1	b0
V4L2_PIX_FMT_BGR666	‘BGRH’		b5	b4	b3	b2	b1	b0	g5	g4		g3	g2	g1	g0	r5	r4	r3	r2		r1	r0
V4L2_PIX_FMT_ABGR32	‘AR24’		b7	b6	b5	b4	b3	b2	b1	b0		g7	g6	g5	g4	g3	g2	g1	g0		r7	r6	r5	r4	r3	r2	r1	r0		a7	a6	a5	a4	a3	a2	a1	a0
V4L2_PIX_FMT_XBGR32	‘XR24’		b7	b6	b5	b4	b3	b2	b1	b0		g7	g6	g5	g4	g3	g2	g1	g0		r7	r6	r5	r4	r3	r2	r1	r0
V4L2_PIX_FMT_ARGB32	‘BA24’		a7	a6	a5	a4	a3	a2	a1	a0		r7	r6	r5	r4	r3	r2	r1	r0		g7	g6	g5	g4	g3	g2	g1	g0		b7	b6	b5	b4	b3	b2	b1	b0
V4L2_PIX_FMT_XRGB32	‘BX24’											r7	r6	r5	r4	r3	r2	r1	r0		g7	g6	g5	g4	g3	g2	g1	g0		b7	b6	b5	b4	b3	b2	b1	b0

Note

Bit 7 is the most significant bit.

The usage and value of the alpha bits (a) in the ARGB and ABGR formats (collectively referred to as alpha formats) depend on the device type and hardware operation. Capture devices (including capture queues of mem-to-mem devices) fill the alpha component in memory. When the device outputs an alpha channel the alpha component will have a meaningful value. Otherwise, when the device doesn’t output an alpha channel but can set the alpha bit to a user-configurable value, the V4L2_CID_ALPHA_COMPONENT control is used to specify that alpha value, and the alpha component of all pixels will be set to the value specified by that control. Otherwise a corresponding format without an alpha component (XRGB or XBGR) must be used instead of an alpha format.

Output devices (including output queues of mem-to-mem devices and video output overlay devices) read the alpha component from memory. When the device processes the alpha channel the alpha component must be filled with meaningful values by applications. Otherwise a corresponding format without an alpha component (XRGB or XBGR) must be used instead of an alpha format.

The XRGB and XBGR formats contain undefined bits (-). Applications, devices and drivers must ignore those bits, for both Video Capture Interface and Video Output Interface devices.

Byte Order. Each cell is one byte.

RGB byte order

start + 0:

B00

G00

R00

B01

G01

R01

B02

G02

R02

B03

G03

R03

start + 12:

B10

G10

R10

B11

G11

R11

B12

G12

R12

B13

G13

R13

start + 24:

B20

G20

R20

B21

G21

R21

B22

G22

R22

B23

G23

R23

start + 36:

B30

G30

R30

B31

G31

R31

B32

G32

R32

B33

G33

R33

Formats defined in Deprecated Packed RGB Image Formats are deprecated and must not be used by new drivers. They are documented here for reference. The meaning of their alpha bits (a) is ill-defined and interpreted as in either the corresponding ARGB or XRGB format, depending on the driver.

Deprecated Packed RGB Image Formats

Identifier	Code		Byte 0 in memory									Byte 1									Byte 2									Byte 3
		Bit	7	6	5	4	3	2	1	0		7	6	5	4	3	2	1	0		7	6	5	4	3	2	1	0		7	6	5	4	3	2	1	0
V4L2_PIX_FMT_RGB444	‘R444’		g3	g2	g1	g0	b3	b2	b1	b0		a3	a2	a1	a0	r3	r2	r1	r0
V4L2_PIX_FMT_RGB555	‘RGBO’		g2	g1	g0	b4	b3	b2	b1	b0		a	r4	r3	r2	r1	r0	g4	g3
V4L2_PIX_FMT_RGB555X	‘RGBQ’		a	r4	r3	r2	r1	r0	g4	g3		g2	g1	g0	b4	b3	b2	b1	b0
V4L2_PIX_FMT_BGR32	‘BGR4’		b7	b6	b5	b4	b3	b2	b1	b0		g7	g6	g5	g4	g3	g2	g1	g0		r7	r6	r5	r4	r3	r2	r1	r0		a7	a6	a5	a4	a3	a2	a1	a0
V4L2_PIX_FMT_RGB32	‘RGB4’		a7	a6	a5	a4	a3	a2	a1	a0		r7	r6	r5	r4	r3	r2	r1	r0		g7	g6	g5	g4	g3	g2	g1	g0		b7	b6	b5	b4	b3	b2	b1	b0

A test utility to determine which RGB formats a driver actually supports is available from the LinuxTV v4l-dvb repository. See https://linuxtv.org/repo/ for access instructions.