Re: [PATCH v5 2/7] v4l2: add support for colorspace conversion API (CSC) for video capture

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On 03/07/2020 19:10, Dafna Hirschfeld wrote:
> For video capture it is the driver that reports the colorspace,
> Y'CbCr/HSV encoding, quantization range and transfer function

In a lot of places in this series the colorimetry parameters are
ordered as colorspace, Y'CbCr/HSV encoding, quantization range and
transfer function, but 'transfer function' should come after
'colorspace'.

I.e. the linear RGB values using a specific colorspace are passed
through the transfer function (aka gamma), pixel encoding and finally
the quantization step. So this order should be kept in both code
and documentation wherever possible.

> used by the video, and there is no way to request something
> different, even though many HDTV receivers have some sort of
> colorspace conversion capabilities.
> 
> For output video this feature already exists since the application
> specifies this information for the video format it will send out, and
> the transmitter will enable any available CSC if a format conversion has
> to be performed in order to match the capabilities of the sink.
> 
> For video capture we propose adding new v4l2_pix_format flag:
> V4L2_PIX_FMT_FLAG_SET_CSC. The flag is set by the application,
> the driver will interpret the colorspace, ycbcr_enc/hsv_enc, quantization
> and xfer_func fields as the requested colorspace information and will

So reorder above,

> attempt to do the conversion it supports.
> 
> Drivers set the flags
> V4L2_FMT_FLAG_CSC_COLORSPACE,
> V4L2_FMT_FLAG_CSC_YCBCR_ENC,
> V4L2_FMT_FLAG_CSC_HSV_ENC,
> V4L2_FMT_FLAG_CSC_QUANTIZATION,
> V4L2_FMT_FLAG_CSC_XFER_FUNC,

and here (and combine the two ENCs to:

V4L2_FMT_FLAG_CSC_YCBCR_ENC/V4L2_FMT_FLAG_CSC_HSV_ENC,

> in the flags field of the struct v4l2_fmtdesc during enumeration to
> indicate that they support colorspace conversion for the respective field.
> 
> Drivers do not have to actually look at the flags. If the flags are not
> set, then the fields 'colorspace', 'ycbcr_enc/hsv_enc', 'quantization'
> and 'xfer_func' are set to the default values by the core, i.e. just

Reorder.

> pass on the received format without conversion.
> 
> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> Signed-off-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@xxxxxxxxxxxxx>
> ---
>  .../media/v4l/pixfmt-v4l2-mplane.rst          | 16 ++---
>  .../userspace-api/media/v4l/pixfmt-v4l2.rst   | 64 +++++++++++++++++--
>  .../media/v4l/vidioc-enum-fmt.rst             | 35 ++++++++++
>  .../media/videodev2.h.rst.exceptions          |  5 ++
>  include/uapi/linux/videodev2.h                |  6 ++
>  5 files changed, 109 insertions(+), 17 deletions(-)
> 
> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-v4l2-mplane.rst b/Documentation/userspace-api/media/v4l/pixfmt-v4l2-mplane.rst
> index 444b4082684c..66f3365d7b72 100644
> --- a/Documentation/userspace-api/media/v4l/pixfmt-v4l2-mplane.rst
> +++ b/Documentation/userspace-api/media/v4l/pixfmt-v4l2-mplane.rst
> @@ -105,29 +105,21 @@ describing all planes of that format.
>      * - __u8
>        - ``ycbcr_enc``
>        - Y'CbCr encoding, from enum :c:type:`v4l2_ycbcr_encoding`.
> -        This information supplements the ``colorspace`` and must be set by
> -	the driver for capture streams and by the application for output
> -	streams, see :ref:`colorspaces`.
> +	See struct :c:type:`v4l2_pix_format`.
>      * - __u8
>        - ``hsv_enc``
>        - HSV encoding, from enum :c:type:`v4l2_hsv_encoding`.
> -        This information supplements the ``colorspace`` and must be set by
> -	the driver for capture streams and by the application for output
> -	streams, see :ref:`colorspaces`.
> +	See struct :c:type:`v4l2_pix_format`.
>      * - }
>        -
>      * - __u8
>        - ``quantization``
>        - Quantization range, from enum :c:type:`v4l2_quantization`.
> -        This information supplements the ``colorspace`` and must be set by
> -	the driver for capture streams and by the application for output
> -	streams, see :ref:`colorspaces`.
> +	See struct :c:type:`v4l2_pix_format`.
>      * - __u8
>        - ``xfer_func``
>        - Transfer function, from enum :c:type:`v4l2_xfer_func`.
> -        This information supplements the ``colorspace`` and must be set by
> -	the driver for capture streams and by the application for output
> -	streams, see :ref:`colorspaces`.
> +	See struct :c:type:`v4l2_pix_format`.
>      * - __u8
>        - ``reserved[7]``
>        - Reserved for future extensions. Should be zeroed by drivers and
> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-v4l2.rst b/Documentation/userspace-api/media/v4l/pixfmt-v4l2.rst
> index 56a2952de873..d9f8f7eb7098 100644
> --- a/Documentation/userspace-api/media/v4l/pixfmt-v4l2.rst
> +++ b/Documentation/userspace-api/media/v4l/pixfmt-v4l2.rst
> @@ -116,7 +116,14 @@ Single-planar format structure
>        - Image colorspace, from enum :c:type:`v4l2_colorspace`.
>          This information supplements the ``pixelformat`` and must be set
>  	by the driver for capture streams and by the application for
> -	output streams, see :ref:`colorspaces`.
> +	output streams, see :ref:`colorspaces`. If the application sets the
> +	flag ``V4L2_PIX_FMT_FLAG_SET_CSC`` then the application can set
> +	this field for a capture stream to request a specific colorspace
> +	for the captured image data. If the driver cannot handle requested
> +	conversion, it will return another supported colorspace.
> +	The driver indicates that colorspace conversion is supported by setting
> +	the flag V4L2_FMT_FLAG_CSC_COLORSPACE in the corresponding struct
> +	:c:type:`v4l2_fmtdesc` during enumeration. See :ref:`fmtdesc-flags`.
>      * - __u32
>        - ``priv``
>        - This field indicates whether the remaining fields of the
> @@ -153,13 +160,29 @@ Single-planar format structure
>        - Y'CbCr encoding, from enum :c:type:`v4l2_ycbcr_encoding`.
>          This information supplements the ``colorspace`` and must be set by
>  	the driver for capture streams and by the application for output
> -	streams, see :ref:`colorspaces`.
> +	streams, see :ref:`colorspaces`. If the application sets the
> +	flag ``V4L2_PIX_FMT_FLAG_SET_CSC`` then the application can set
> +	this field for a capture stream to request a specific Y'CbCr encoding
> +	for the captured image data. If the driver cannot handle requested
> +	conversion, it will return another supported encoding.
> +	This field is ignored for HSV pixelformats. The driver indicates that
> +	ycbcr_enc conversion is supported by setting the flag
> +	V4L2_FMT_FLAG_CSC_YCBCR_ENC in the corresponding struct
> +	:c:type:`v4l2_fmtdesc` during enumeration. See :ref:`fmtdesc-flags`.
>      * - __u32
>        - ``hsv_enc``
>        - HSV encoding, from enum :c:type:`v4l2_hsv_encoding`.
>          This information supplements the ``colorspace`` and must be set by
>  	the driver for capture streams and by the application for output
> -	streams, see :ref:`colorspaces`.
> +	streams, see :ref:`colorspaces`. If the application sets the flag
> +	``V4L2_PIX_FMT_FLAG_SET_CSC`` then the application can set this
> +	field for a capture stream to request a specific HSV encoding for the
> +	captured image data. If the driver cannot handle requested
> +	conversion, it will return another supported encoding.
> +	This field is ignored for non-HSV pixelformats. The driver indicates
> +	that hsv_enc conversion is supported by setting the flag
> +	V4L2_FMT_FLAG_CSC_HSV_ENC in the corresponding struct
> +	:c:type:`v4l2_fmtdesc` during enumeration. See :ref:`fmtdesc-flags`.
>      * - }
>        -
>      * - __u32
> @@ -167,13 +190,27 @@ Single-planar format structure
>        - Quantization range, from enum :c:type:`v4l2_quantization`.
>          This information supplements the ``colorspace`` and must be set by
>  	the driver for capture streams and by the application for output
> -	streams, see :ref:`colorspaces`.
> +	streams, see :ref:`colorspaces`. If the application sets the flag
> +	``V4L2_PIX_FMT_FLAG_SET_CSC`` then the application can set
> +	this field for a capture stream to request a specific quantization
> +	range for the captured image data. If the driver cannot handle requested
> +	conversion, it will return another supported encoding.
> +	The driver indicates that quantization conversion is supported by setting
> +	the flag V4L2_FMT_FLAG_CSC_QUANTIZATION in the corresponding struct
> +	:c:type:`v4l2_fmtdesc` during enumeration. See :ref:`fmtdesc-flags`.
>      * - __u32
>        - ``xfer_func``
>        - Transfer function, from enum :c:type:`v4l2_xfer_func`.
>          This information supplements the ``colorspace`` and must be set by
>  	the driver for capture streams and by the application for output
> -	streams, see :ref:`colorspaces`.
> +	streams, see :ref:`colorspaces`. If the application sets the flag
> +	``V4L2_PIX_FMT_FLAG_SET_CSC`` then the application can set
> +	this field for a capture stream to request a specific Transfer function
> +	for the captured image data. If the driver cannot handle requested
> +	conversion, it will return another supported Transfer function.
> +	The driver indicates that xfer_func conversion is supported by setting
> +	the flag V4L2_FMT_FLAG_CSC_XFER_FUNC in the corresponding struct
> +	:c:type:`v4l2_fmtdesc` during enumeration. See :ref:`fmtdesc-flags`.
>  
>  .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
>  
> @@ -191,3 +228,20 @@ Single-planar format structure
>  	by RGBA values (128, 192, 255, 128), the same pixel described with
>  	premultiplied colors would be described by RGBA values (64, 96,
>  	128, 128)
> +    * .. _`v4l2-pix-fmt-flag-set-csc`:
> +
> +      - ``V4L2_PIX_FMT_FLAG_SET_CSC``
> +      - 0x00000002
> +      - Set by the application. It is only used for capture and is
> +        ignored for output streams. If set, then request the device to do
> +	colorspace conversion from the received colorspace to the requested
> +	colorspace values. If colorimetry field (``colorspace``, ``ycbcr_enc``,

If -> If the

> +	``hsv_enc``, ``quantization`` or ``xfer_func``) is set to 0, then that

reorder ``xfer_func``.

> +	colorimetry setting will remain unchanged from what was received. So to
> +	change the quantization only the ``quantization`` field shall be set to
> +	non-zero values (``V4L2_QUANTIZATION_FULL_RANGE`` or
> +	``V4L2_QUANTIZATION_LIM_RANGE``) and all other colorimetry fields shall
> +	be set to 0.
> +
> +	To check which conversions are supported by the hardware for the current
> +	pixel format, see :ref:`fmtdesc-flags`.
> diff --git a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
> index 05835e04c20b..98595dd48557 100644
> --- a/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
> +++ b/Documentation/userspace-api/media/v4l/vidioc-enum-fmt.rst
> @@ -198,6 +198,41 @@ the ``mbus_code`` field is handled differently:
>  	This flag can only be used in combination with the
>  	``V4L2_FMT_FLAG_COMPRESSED`` flag, since this applies to
>          compressed formats only. This flag is valid for stateful encoders only.
> +    * - ``V4L2_FMT_FLAG_CSC_COLORSPACE``
> +      - 0x0020
> +      - The driver allows the application to try to change the default
> +	colorspace. This flag is relevant only for capture devices.
> +	The application can ask to configure the colorspace of the capture device
> +	when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with
> +	:ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set.
> +    * - ``V4L2_FMT_FLAG_CSC_YCBCR_ENC``
> +      - 0x0040
> +      - The driver allows the application to try to change the default
> +	Y'CbCr encoding. This flag is relevant only for capture devices.
> +	The application can ask to configure the ycbcr_enc of the capture device
> +	when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with
> +	:ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set.
> +    * - ``V4L2_FMT_FLAG_CSC_HSV_ENC``
> +      - 0x0040
> +      - The driver allows the application to try to change the default
> +	HSV encoding. This flag is relevant only for capture devices.
> +	The application can ask to configure the hsv_enc of the capture device
> +	when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with
> +	:ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set.
> +    * - ``V4L2_FMT_FLAG_CSC_QUANTIZATION``
> +      - 0x0080
> +      - The driver allows the application to try to change the default
> +	quantization. This flag is relevant only for capture devices.
> +	The application can ask to configure the quantization of the capture
> +	device when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with
> +	:ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set.
> +    * - ``V4L2_FMT_FLAG_CSC_XFER_FUNC``
> +      - 0x0100

Reorder, the flag values also change.

> +      - The driver allows the application to try to change the default
> +	quantization. This flag is relevant only for capture devices.
> +	The application can ask to configure the quantization of the capture
> +	device when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with
> +	:ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set.
>  
>  
>  Return Value
> diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> index 659799cc1eca..faa19e7d241b 100644
> --- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> +++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> @@ -188,6 +188,11 @@ replace define V4L2_FMT_FLAG_EMULATED fmtdesc-flags
>  replace define V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM fmtdesc-flags
>  replace define V4L2_FMT_FLAG_DYN_RESOLUTION fmtdesc-flags
>  replace define V4L2_FMT_FLAG_ENC_CAP_FRAME_INTERVAL fmtdesc-flags
> +replace define V4L2_FMT_FLAG_CSC_COLORSPACE fmtdesc-flags
> +replace define V4L2_FMT_FLAG_CSC_YCBCR_ENC fmtdesc-flags
> +replace define V4L2_FMT_FLAG_CSC_HSV_ENC fmtdesc-flags
> +replace define V4L2_FMT_FLAG_CSC_QUANTIZATION fmtdesc-flags
> +replace define V4L2_FMT_FLAG_CSC_XFER_FUNC fmtdesc-flags

Reorder

>  
>  # V4L2 timecode types
>  replace define V4L2_TC_TYPE_24FPS timecode-type
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 303805438814..76610509d670 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -776,6 +776,7 @@ struct v4l2_pix_format {
>  
>  /* Flags */
>  #define V4L2_PIX_FMT_FLAG_PREMUL_ALPHA	0x00000001
> +#define V4L2_PIX_FMT_FLAG_SET_CSC	0x00000002
>  
>  /*
>   *	F O R M A T   E N U M E R A T I O N
> @@ -795,6 +796,11 @@ struct v4l2_fmtdesc {
>  #define V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM	0x0004
>  #define V4L2_FMT_FLAG_DYN_RESOLUTION		0x0008
>  #define V4L2_FMT_FLAG_ENC_CAP_FRAME_INTERVAL	0x0010
> +#define V4L2_FMT_FLAG_CSC_COLORSPACE		0x0020
> +#define V4L2_FMT_FLAG_CSC_YCBCR_ENC		0x0040
> +#define V4L2_FMT_FLAG_CSC_HSV_ENC		V4L2_FMT_FLAG_CSC_YCBCR_ENC
> +#define V4L2_FMT_FLAG_CSC_QUANTIZATION		0x0080
> +#define V4L2_FMT_FLAG_CSC_XFER_FUNC		0x0100

Reorder and renumber the values accordingly.

>  
>  	/* Frame Size and frame rate enumeration */
>  /*
> 

Regards,

	Hans



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