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 13cf36a8cd5c..c01a949e7c11 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-m420.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-m420.rst @@ -67,60 +67,5 @@ 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 dd2f38129fe6..692117bf83ad 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-nv12.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-nv12.rst @@ -72,58 +72,5 @@ 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 250f8b977605..002b361d5a9b 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-nv12m.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-nv12m.rst @@ -84,61 +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-nv16.rst b/Documentation/userspace-api/media/v4l/pixfmt-nv16.rst index 22295fc0c359..e6307843d848 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-nv16.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-nv16.rst @@ -80,74 +80,5 @@ 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 812bf2ccabf0..58e97205d41f 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-nv16m.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-nv16m.rst @@ -84,74 +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 - * - - - - - 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 bae975fb14f6..1abc3066b712 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-uyvy.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-uyvy.rst @@ -66,45 +66,5 @@ 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 aff8588b67a9..4fd0630a83a4 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-vyuy.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-vyuy.rst @@ -66,43 +66,5 @@ 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 d14cedf8f317..bb83eb6db3e5 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-y41p.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-y41p.rst @@ -89,63 +89,5 @@ 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 de2e519adc60..d79cd46d5055 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv410.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv410.rst @@ -68,60 +68,5 @@ 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 998aa9b1328f..8a70eeca8d83 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv411p.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv411p.rst @@ -76,40 +76,5 @@ 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 f1c7baf32685..a36ec8d6d8a4 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv420.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv420.rst @@ -77,67 +77,5 @@ 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 cd20a57e0621..c2cf17b9743c 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv420m.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv420m.rst @@ -86,67 +86,5 @@ 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 32bf15e1426e..f92b54853fc9 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv422m.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv422m.rst @@ -97,45 +97,5 @@ 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 b178be558361..33e6b923e325 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv422p.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv422p.rst @@ -85,45 +85,5 @@ 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 90bdee2e2b0d..7c03cc5b07d9 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv444m.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv444m.rst @@ -107,35 +107,4 @@ 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 ca073a5098a9..4d5773922ba1 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yuyv.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuyv.rst @@ -69,50 +69,5 @@ 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 81ebec525ae5..14b56b611349 100644 --- a/Documentation/userspace-api/media/v4l/pixfmt-yvyu.rst +++ b/Documentation/userspace-api/media/v4l/pixfmt-yvyu.rst @@ -66,43 +66,5 @@ 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 4a05a105a9e6..79a4fda566c6 100644 --- a/Documentation/userspace-api/media/v4l/yuv-formats.rst +++ b/Documentation/userspace-api/media/v4l/yuv-formats.rst @@ -14,11 +14,251 @@ 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
