2.7.1.1. Packed YUV formats

Similarly to the packed RGB formats, the packed YUV formats store the Y, Cb and Cr components consecutively in memory. They may apply subsampling to the chroma components and thus differ in how they interlave the three components.

Note

  • In all the tables that follow, bit 7 is the most significant bit in a byte.
  • ‘Y’, ‘Cb’ and ‘Cr’ denote bits of the luma, blue chroma (also known as ‘U’) and red chroma (also known as ‘V’) components respectively. ‘A’ denotes bits of the alpha component (if supported by the format), and ‘X’ denotes padding bits.

2.7.1.1.1. 4:4:4 Subsampling

These formats do not subsample the chroma components and store each pixels as a full triplet of Y, Cb and Cr values.

The next table lists the packed YUV 4:4:4 formats with less than 8 bits per component. They are named based on the order of the Y, Cb and Cr components as seen in a 16-bit word, which is then stored in memory in little endian byte order, and on the number of bits for each component. For instance the YUV565 format stores a pixel in a 16-bit word [15:0] laid out at as [Y’4-0 Cb5-0 Cr4-0], and stored in memory in two bytes, [Cb2-0 Cr4-0] followed by [Y’4-0 Cb5-3].

Packed YUV 4:4:4 Image Formats (less than 8bpc)
Identifier Code Byte 0 in memory Byte 1
    7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
V4L2_PIX_FMT_YUV444 ‘Y444’ Cb3 Cb2 Cb1 Cb0 Cr3 Cr2 Cr1 Cr0 a3 a2 a1 a0 Y’3 Y’2 Y’1

Y’0
V4L2_PIX_FMT_YUV555 ‘YUVO’ Cb2 Cb1 Cb0 Cr4 Cr3 Cr2 Cr1 Cr0 a Y’4 Y’3 Y’2 Y’1 Y’0 Cb4

Cb3
V4L2_PIX_FMT_YUV565 ‘YUVP’ Cb2 Cb1 Cb0 Cr4 Cr3 Cr2 Cr1 Cr0 Y’4 Y’3 Y’2 Y’1 Y’0 Cb5 Cb4

Cb3

Note

For the YUV444 and YUV555 formats, the value of alpha bits is undefined when reading from the driver, ignored when writing to the driver, except when alpha blending has been negotiated for a Video Overlay or Video Output Overlay.

The next table lists the packed YUV 4:4:4 formats with 8 bits per component. They are named based on the order of the Y, Cb and Cr components as stored in memory, and on the total number of bits per pixel. For instance, the VUYX32 format stores a pixel with Cr7-0 in the first byte, Cb7-0 in the second byte and Y’7-0 in the third byte.

Packed YUV Image Formats (8bpc)
Identifier Code Byte 0 Byte 1 Byte 2 Byte 3
V4L2_PIX_FMT_YUV32 ‘YUV4’ A7-0 Y’7-0 Cb7-0

Cr7-0
V4L2_PIX_FMT_AYUV32 ‘AYUV’ A7-0 Y’7-0 Cb7-0

Cr7-0
V4L2_PIX_FMT_XYUV32 ‘XYUV’ X7-0 Y’7-0 Cb7-0

Cr7-0
V4L2_PIX_FMT_VUYA32 ‘VUYA’ Cr7-0 Cb7-0 Y’7-0

A7-0
V4L2_PIX_FMT_VUYX32 ‘VUYX’ Cr7-0 Cb7-0 Y’7-0

X7-0

Note

  • The alpha component is expected to contain a meaningful value that can be used by drivers and applications.
  • The padding bits contain undefined values that must be ignored by all applications and drivers.

2.7.1.1.2. 4:2:2 Subsampling

These formats, commonly referred to as YUYV or YUY2, subsample the chroma components horizontally by 2, storing 2 pixels in 4 bytes.

Packed YUV 4:2:2 Formats
Identifier Code Byte 0 Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Byte 7
V4L2_PIX_FMT_UYVY ‘UYVY’ Cb0 Y’0 Cr0 Y’1 Cb2 Y’2 Cr2

Y’3
V4L2_PIX_FMT_VYUY ‘VYUY’ Cr0 Y’0 Cb0 Y’1 Cr2 Y’2 Cb2

Y’3
V4L2_PIX_FMT_YUYV ‘YUYV’ Y’0 Cb0 Y’1 Cr0 Y’2 Cb2 Y’3

Cr2
V4L2_PIX_FMT_YVYU ‘YVYU’ Y’0 Cr0 Y’1 Cb0 Y’2 Cr2 Y’3

Cb2

Color Sample Location: Chroma samples are interstitially sited horizontally.

2.7.1.1.3. 4:1:1 Subsampling

This format subsamples the chroma components horizontally by 4, storing 8 pixels in 12 bytes.

Packed YUV 4:1:1 Formats
Identifier Code Byte 0 Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Byte 7 Byte 8 Byte 9 Byte 10 Byte 11
V4L2_PIX_FMT_Y41P ‘Y41P’ Cb0 Y’0 Cr0 Y’1 Cb4 Y’2 Cr4 Y’3 Y’4 Y’5 Y’6

Y’7

Note

Do not confuse V4L2_PIX_FMT_Y41P with V4L2_PIX_FMT_YUV411P. Y41P is derived from “YUV 4:1:1 packed”, while YUV411P stands for “YUV 4:1:1 planar”.

Color Sample Location: Chroma samples are interstitially sited horizontally.