Document YUV subsampling, including chroma spatial siting, and replace the siting examples in individual formats by references to the common documentation. Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> --- .../userspace-api/media/v4l/pixfmt-m420.rst | 59 +---- .../userspace-api/media/v4l/pixfmt-nv12.rst | 57 +--- .../userspace-api/media/v4l/pixfmt-nv12m.rst | 60 +---- .../userspace-api/media/v4l/pixfmt-nv16.rst | 73 +---- .../userspace-api/media/v4l/pixfmt-nv16m.rst | 73 +---- .../userspace-api/media/v4l/pixfmt-uyvy.rst | 44 +-- .../userspace-api/media/v4l/pixfmt-vyuy.rst | 42 +-- .../userspace-api/media/v4l/pixfmt-y41p.rst | 62 +---- .../userspace-api/media/v4l/pixfmt-yuv410.rst | 59 +---- .../media/v4l/pixfmt-yuv411p.rst | 39 +-- .../userspace-api/media/v4l/pixfmt-yuv420.rst | 66 +---- .../media/v4l/pixfmt-yuv420m.rst | 66 +---- .../media/v4l/pixfmt-yuv422m.rst | 44 +-- .../media/v4l/pixfmt-yuv422p.rst | 44 +-- .../media/v4l/pixfmt-yuv444m.rst | 33 +-- .../userspace-api/media/v4l/pixfmt-yuyv.rst | 49 +--- .../userspace-api/media/v4l/pixfmt-yvyu.rst | 42 +-- .../userspace-api/media/v4l/yuv-formats.rst | 250 +++++++++++++++++- 18 files changed, 278 insertions(+), 884 deletions(-) diff --git a/Documentation/userspace-api/media/v4l/pixfmt-m420.rst b/Documentation/userspace-api/media/v4l/pixfmt-m420.rst index 5180bbe16c6e..38c2bde6a87d 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-m420.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-m420.rst @@ -74,60 +74,5 @@ Each cell is one byte. **Color Sample Location:** - - - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - - - 1 - - 2 - - - - 3 - * - 0 - - Y - - - - Y - - Y - - - - Y - * - - - - - C - - - - - - C - - - * - 1 - - Y - - - - Y - - Y - - - - Y - * - - * - 2 - - Y - - - - Y - - Y - - - - Y - * - - - - - C - - - - - - C - - - * - 3 - - Y - - - - Y - - Y - - - - Y +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally and vertically. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-nv12.rst b/Documentation/userspace-api/media/v4l/pixfmt-nv12.rst index 19d47b38e02a..26d7df9e1298 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-nv12.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-nv12.rst @@ -79,58 +79,5 @@ Each cell is one byte. **Color Sample Location:** - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - - - 1 - - 2 - - - - 3 - * - 0 - - Y - - - - Y - - Y - - - - Y - * - - - - - C - - - - - - C - - - * - 1 - - Y - - - - Y - - Y - - - - Y - * - - * - 2 - - Y - - - - Y - - Y - - - - Y - * - - - - - C - - - - - - C - - - * - 3 - - Y - - - - Y - - Y - - - - Y +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally and vertically. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-nv12m.rst b/Documentation/userspace-api/media/v4l/pixfmt-nv12m.rst index 115ea603c13f..752c42a0f52c 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-nv12m.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-nv12m.rst @@ -91,61 +91,5 @@ Each cell is one byte. **Color Sample Location:** - - - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - - - 1 - - 2 - - - - 3 - * - 0 - - Y - - - - Y - - Y - - - - Y - * - - - - - C - - - - - - C - - - * - 1 - - Y - - - - Y - - Y - - - - Y - * - - * - 2 - - Y - - - - Y - - Y - - - - Y - * - - - - - C - - - - - - - - C - - - * - 3 - - Y - - - - Y - - Y - - - - Y +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally and vertically. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-nv16.rst b/Documentation/userspace-api/media/v4l/pixfmt-nv16.rst index 977636fc98d6..82659557daae 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-nv16.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-nv16.rst @@ -87,74 +87,5 @@ Each cell is one byte. **Color Sample Location:** - - - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - - - 1 - - 2 - - - - 3 - * - 0 - - Y - - - - Y - - Y - - - - Y - * - - - - - C - - - - - - C - - - * - 1 - - Y - - - - Y - - Y - - - - Y - * - - - - - C - - - - - - C - - - * - - * - 2 - - Y - - - - Y - - Y - - - - Y - * - - - - - C - - - - - - C - - - * - 3 - - Y - - - - Y - - Y - - - - Y - * - - - - - C - - - - - - C - - +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-nv16m.rst b/Documentation/userspace-api/media/v4l/pixfmt-nv16m.rst index cf33942d942d..3e8ae54c846e 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-nv16m.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-nv16m.rst @@ -91,74 +91,5 @@ Each cell is one byte. **Color Sample Location:** - - - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - - - 1 - - 2 - - - - 3 - * - 0 - - Y - - - - Y - - Y - - - - Y - * - - - - - C - - - - - - C - - - * - 1 - - Y - - - - Y - - Y - - - - Y - * - - - - - C - - - - - - C - - - * - - * - 2 - - Y - - - - Y - - Y - - - - Y - * - - - - - C - - - - - - C - - - * - 3 - - Y - - - - Y - - Y - - - - Y - * - - - - - C - - - - - - C - - +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-uyvy.rst b/Documentation/userspace-api/media/v4l/pixfmt-uyvy.rst index 776cb37f76f1..5571d771af89 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-uyvy.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-uyvy.rst @@ -73,45 +73,5 @@ Each cell is one byte. **Color Sample Location:** - - - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - - - 1 - - 2 - - - - 3 - * - 0 - - Y - - C - - Y - - Y - - C - - Y - * - 1 - - Y - - C - - Y - - Y - - C - - Y - * - 2 - - Y - - C - - Y - - Y - - C - - Y - * - 3 - - Y - - C - - Y - - Y - - C - - Y +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-vyuy.rst b/Documentation/userspace-api/media/v4l/pixfmt-vyuy.rst index 6cd574e78e4c..3d0dce59c591 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-vyuy.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-vyuy.rst @@ -73,43 +73,5 @@ Each cell is one byte. **Color Sample Location:** - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - - - 1 - - - - 2 - - 3 - * - 0 - - Y - - C - - Y - - Y - - C - - Y - * - 1 - - Y - - C - - Y - - Y - - C - - Y - * - 2 - - Y - - C - - Y - - Y - - C - - Y - * - 3 - - Y - - C - - Y - - Y - - C - - Y +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-y41p.rst b/Documentation/userspace-api/media/v4l/pixfmt-y41p.rst index 211afd7593cc..880e87490b25 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-y41p.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-y41p.rst @@ -96,63 +96,5 @@ Each cell is one byte. **Color Sample Location:** - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - 1 - - - - 2 - - 3 - - 4 - - 5 - - - - 6 - - 7 - * - 0 - - Y - - Y - - C - - Y - - Y - - Y - - Y - - C - - Y - - Y - * - 1 - - Y - - Y - - C - - Y - - Y - - Y - - Y - - C - - Y - - Y - * - 2 - - Y - - Y - - C - - Y - - Y - - Y - - Y - - C - - Y - - Y - * - 3 - - Y - - Y - - C - - Y - - Y - - Y - - Y - - C - - Y - - Y +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-yuv410.rst b/Documentation/userspace-api/media/v4l/pixfmt-yuv410.rst index 1d20115f2b1d..b4b0bcd96f6e 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv410.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv410.rst @@ -75,60 +75,5 @@ Each cell is one byte. **Color Sample Location:** - - - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - - - 1 - - - - 2 - - - - 3 - * - 0 - - Y - - - - Y - - - - Y - - - - Y - * - - * - 1 - - Y - - - - Y - - - - Y - - - - Y - * - - - - - - - - - C - - - - - - - * - 2 - - Y - - - - Y - - - - Y - - - - Y - * - - * - 3 - - Y - - - - Y - - - - Y - - - - Y +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally and vertically. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-yuv411p.rst b/Documentation/userspace-api/media/v4l/pixfmt-yuv411p.rst index 967ba7ce41a2..65d5a9b54500 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv411p.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv411p.rst @@ -83,40 +83,5 @@ Each cell is one byte. **Color Sample Location:** - - - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - 1 - - - - 2 - - 3 - * - 0 - - Y - - Y - - C - - Y - - Y - * - 1 - - Y - - Y - - C - - Y - - Y - * - 2 - - Y - - Y - - C - - Y - - Y - * - 3 - - Y - - Y - - C - - Y - - Y +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-yuv420.rst b/Documentation/userspace-api/media/v4l/pixfmt-yuv420.rst index 7cb685cc8289..cc1a5df03248 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv420.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv420.rst @@ -84,67 +84,5 @@ Each cell is one byte. **Color Sample Location:** - - - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - - - 1 - - - - 2 - - - - 3 - * - 0 - - Y - - - - Y - - - - Y - - - - Y - * - - - - - C - - - - - - - - C - - - * - 1 - - Y - - - - Y - - - - Y - - - - Y - * - - * - 2 - - Y - - - - Y - - - - Y - - - - Y - * - - - - - C - - - - - - - - C - - - * - 3 - - Y - - - - Y - - - - Y - - - - Y +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally and vertically. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-yuv420m.rst b/Documentation/userspace-api/media/v4l/pixfmt-yuv420m.rst index 80c14d4f5acb..d189903d8ff3 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv420m.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv420m.rst @@ -93,67 +93,5 @@ Each cell is one byte. **Color Sample Location:** - - - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - - - 1 - - - - 2 - - - - 3 - * - 0 - - Y - - - - Y - - - - Y - - - - Y - * - - - - - C - - - - - - - - C - - - * - 1 - - Y - - - - Y - - - - Y - - - - Y - * - - * - 2 - - Y - - - - Y - - - - Y - - - - Y - * - - - - - C - - - - - - - - C - - - * - 3 - - Y - - - - Y - - - - Y - - - - Y +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally and vertically. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-yuv422m.rst b/Documentation/userspace-api/media/v4l/pixfmt-yuv422m.rst index 29b78480ccad..5ffea984a160 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv422m.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv422m.rst @@ -104,45 +104,5 @@ Each cell is one byte. **Color Sample Location:** - - - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - - - 1 - - 2 - - - - 3 - * - 0 - - Y - - C - - Y - - Y - - C - - Y - * - 1 - - Y - - C - - Y - - Y - - C - - Y - * - 2 - - Y - - C - - Y - - Y - - C - - Y - * - 3 - - Y - - C - - Y - - Y - - C - - Y +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-yuv422p.rst b/Documentation/userspace-api/media/v4l/pixfmt-yuv422p.rst index 73fde222d820..ee4e7badbf4c 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv422p.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv422p.rst @@ -92,45 +92,5 @@ Each cell is one byte. **Color Sample Location:** - - - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - - - 1 - - 2 - - - - 3 - * - 0 - - Y - - C - - Y - - Y - - C - - Y - * - 1 - - Y - - C - - Y - - Y - - C - - Y - * - 2 - - Y - - C - - Y - - Y - - C - - Y - * - 3 - - Y - - C - - Y - - Y - - C - - Y +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-yuv444m.rst b/Documentation/userspace-api/media/v4l/pixfmt-yuv444m.rst index 7073ac7f842d..52ebc67d7ebe 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv444m.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv444m.rst @@ -114,35 +114,4 @@ Each cell is one byte. **Color Sample Location:** - - - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - 1 - - 2 - - 3 - * - 0 - - YC - - YC - - YC - - YC - * - 1 - - YC - - YC - - YC - - YC - * - 2 - - YC - - YC - - YC - - YC - * - 3 - - YC - - YC - - YC - - YC +Chroma samples are :ref:`co-sited<yuv-chroma-cosited>`. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-yuyv.rst b/Documentation/userspace-api/media/v4l/pixfmt-yuyv.rst index fe70e007787d..0ad1169b221f 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuyv.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuyv.rst @@ -76,50 +76,5 @@ Each cell is one byte. **Color Sample Location:** - - - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - - - 1 - - - - 2 - - - - 3 - * - 0 - - Y - - C - - Y - - - - Y - - C - - Y - * - 1 - - Y - - C - - Y - - - - Y - - C - - Y - * - 2 - - Y - - C - - Y - - - - Y - - C - - Y - * - 3 - - Y - - C - - Y - - - - Y - - C - - Y +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally. diff --git a/Documentation/userspace-api/media/v4l/pixfmt-yvyu.rst b/Documentation/userspace-api/media/v4l/pixfmt-yvyu.rst index 96c1b537d5a0..c9f35d7183c5 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yvyu.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yvyu.rst @@ -73,43 +73,5 @@ Each cell is one byte. **Color Sample Location:** - -.. flat-table:: - :header-rows: 0 - :stub-columns: 0 - - * - - - 0 - - - - 1 - - 2 - - - - 3 - * - 0 - - Y - - C - - Y - - Y - - C - - Y - * - 1 - - Y - - C - - Y - - Y - - C - - Y - * - 2 - - Y - - C - - Y - - Y - - C - - Y - * - 3 - - Y - - C - - Y - - Y - - C - - Y +Chroma samples are :ref:`interstitially sited<yuv-chroma-centered>` +horizontally. diff --git a/Documentation/userspace-api/media/v4l/yuv-formats.rst b/Documentation/userspace-api/media/v4l/yuv-formats.rst index 8ee92d0cd769..77ab71c7d0f5 100644 --- a/Documentation/userspace-api/media/v4l/yuv-formats.rst +++ b/Documentation/userspace-api/media/v4l/yuv-formats.rst @@ -21,11 +21,251 @@ reconstructed by subtracting from the brightness component. See :ref:`colorspaces` for conversion examples. YUV was chosen because early television would only transmit brightness information. To add color in a way compatible with existing receivers a new signal carrier -was added to transmit the color difference signals. Secondary in the YUV -format the U and V components usually have lower resolution than the Y -component. This is an analog video compression technique taking -advantage of a property of the human visual system, being more sensitive -to brightness information. +was added to transmit the color difference signals. + + +Subsampling +=========== + +YUV formats commonly encode images with a lower resolution for the chroma +components than for the luma component. This compression technique, taking +advantage of the human eye being more sensitive to luminance than color +differences, is called chroma subsampling. + +While many combinations of subsampling factors in the horizontal and vertical +direction are possible, common factors are 1 (no subsampling), 2 and 4, with +horizontal subsampling always larger than or equal to vertical subsampling. +Common combinations are named as follows. + +- `4:4:4`: No subsampling +- `4:2:2`: Horizontal subsampling by 2, no vertical subsampling +- `4:2:0`: Horizontal subsampling by 2, vertical subsampling by 2 +- `4:1:1`: Horizontal subsampling by 4, no vertical subsampling +- `4:1:0`: Horizontal subsampling by 4, vertical subsampling by 4 + +Subsampling the chroma component effectively creates chroma values that can be +located in different spatial locations: + +- .. _yuv-chroma-centered: + + The subsampled chroma value may be calculated by simply averaging the chroma + value of two consecutive pixels. It effectively models the chroma of a pixel + sited between the two original pixels. This is referred to as centered or + interstitially sited chroma. + +- .. _yuv-chroma-cosited: + + The other option is to subsample chroma values in a way that place them in + the same spatial sites as the pixels. This may be performed by skipping every + other chroma sample (creating aliasing artifacts), or with filters using an + odd number of taps. This is referred to as co-sited chroma. + +The following examples show different combination of chroma siting in a 4x4 +image. + +.. flat-table:: 4:2:2 subsampling, interstitially sited + :header-rows: 1 + :stub-columns: 1 + + * - + - 0 + - + - 1 + - + - 2 + - + - 3 + * - 0 + - Y + - C + - Y + - + - Y + - C + - Y + * - 1 + - Y + - C + - Y + - + - Y + - C + - Y + * - 2 + - Y + - C + - Y + - + - Y + - C + - Y + * - 3 + - Y + - C + - Y + - + - Y + - C + - Y + +.. flat-table:: 4:2:2 subsampling, co-sited + :header-rows: 1 + :stub-columns: 1 + + * - + - 0 + - + - 1 + - + - 2 + - + - 3 + * - 0 + - Y/C + - + - Y + - + - Y/C + - + - Y + * - 1 + - Y/C + - + - Y + - + - Y/C + - + - Y + * - 2 + - Y/C + - + - Y + - + - Y/C + - + - Y + * - 3 + - Y/C + - + - Y + - + - Y/C + - + - Y + +.. flat-table:: 4:2:0 subsampling, horizontally interstitially sited, vertically co-sited + :header-rows: 1 + :stub-columns: 1 + + * - + - 0 + - + - 1 + - + - 2 + - + - 3 + * - 0 + - Y + - C + - Y + - + - Y + - C + - Y + * - 1 + - Y + - + - Y + - + - Y + - + - Y + * - 2 + - Y + - C + - Y + - + - Y + - C + - Y + * - 3 + - Y + - + - Y + - + - Y + - + - Y + +.. flat-table:: 4:1:0 subsampling, horizontally and vertically interstitially sited + :header-rows: 1 + :stub-columns: 1 + + * - + - 0 + - + - 1 + - + - 2 + - + - 3 + * - 0 + - Y + - + - Y + - + - Y + - + - Y + * - + - + - + - + - + - + - + - + * - 1 + - Y + - + - Y + - + - Y + - + - Y + * - + - + - + - + - C + - + - + - + * - 2 + - Y + - + - Y + - + - Y + - + - Y + * - + - + - + - + - + - + - + - + * - 3 + - Y + - + - Y + - + - Y + - + - Y .. toctree:: -- Regards, Laurent Pinchart
