On 06/09/2024 00:53, Laurent Pinchart wrote:
> Companding refers to compression and expansion of pixel data to fit in a
> smaller range. The control is named V4L2_CID_COMPANDING, and only
> supports compression initially.
>
> Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> ---
> Changes since v1:
>
> - Rename V4L2_COMPANDING_ALAW to V4L2_COMPANDING_COMPRESS
> - Document V4L2_COMPANDING_LINEAR and V4L2_COMPANDING_COMPRESS
> ---
> .../media/v4l/ext-ctrls-image-process.rst | 16 ++++++++++++++++
> drivers/media/v4l2-core/v4l2-ctrls-defs.c | 9 +++++++++
> include/uapi/linux/v4l2-controls.h | 5 +++++
> 3 files changed, 30 insertions(+)
>
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
> index b1c2ab2854af..d529b0a8cd41 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-image-process.rst
> @@ -55,3 +55,19 @@ Image Process Control IDs
> control value divided by e.g. 0x100, meaning that to get no
> digital gain the control value needs to be 0x100. The no-gain
> configuration is also typically the default.
> +
> +``V4L2_CID_COMPANDING (menu)``
> + Companding refers to compression and expansion of pixel data to fit in a
> + smaller range.
> +
> +
> +.. tabularcolumns:: |p{5.7cm}|p{11.8cm}|
> +
> +.. flat-table::
> + :header-rows: 0
> + :stub-columns: 0
> +
> + * - ``V4L2_COMPANDING_LINEAR``
> + - No companding.
> + * - ``V4L2_COMPANDING_COMPRESS``
It's weird that this is called 'COMPRESS',
> + - Compress the data using a device-specific curve.
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> index 1ea52011247a..841e415a88ae 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> @@ -611,6 +611,11 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
> "Cyclic",
> NULL,
> };
> + static const char * const companding[] = {
> + "Linear",
> + "A-Law",
but it is called 'A-Law' here. I think the same name should be used for both
as this is confusing.
Regards,
Hans
> + NULL
> + };
>
> switch (id) {
> case V4L2_CID_MPEG_AUDIO_SAMPLING_FREQ:
> @@ -750,6 +755,8 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
> return camera_orientation;
> case V4L2_CID_MPEG_VIDEO_INTRA_REFRESH_PERIOD_TYPE:
> return intra_refresh_period_type;
> + case V4L2_CID_COMPANDING:
> + return companding;
> default:
> return NULL;
> }
> @@ -1164,6 +1171,7 @@ const char *v4l2_ctrl_get_name(u32 id)
> case V4L2_CID_TEST_PATTERN: return "Test Pattern";
> case V4L2_CID_DEINTERLACING_MODE: return "Deinterlacing Mode";
> case V4L2_CID_DIGITAL_GAIN: return "Digital Gain";
> + case V4L2_CID_COMPANDING: return "Companding";
>
> /* DV controls */
> /* Keep the order of the 'case's the same as in v4l2-controls.h! */
> @@ -1421,6 +1429,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
> case V4L2_CID_CAMERA_ORIENTATION:
> case V4L2_CID_MPEG_VIDEO_INTRA_REFRESH_PERIOD_TYPE:
> case V4L2_CID_HDR_SENSOR_MODE:
> + case V4L2_CID_COMPANDING:
> *type = V4L2_CTRL_TYPE_MENU;
> break;
> case V4L2_CID_LINK_FREQ:
> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
> index 974fd254e573..ca9e25f72886 100644
> --- a/include/uapi/linux/v4l2-controls.h
> +++ b/include/uapi/linux/v4l2-controls.h
> @@ -1225,6 +1225,11 @@ enum v4l2_jpeg_chroma_subsampling {
> #define V4L2_CID_TEST_PATTERN (V4L2_CID_IMAGE_PROC_CLASS_BASE + 3)
> #define V4L2_CID_DEINTERLACING_MODE (V4L2_CID_IMAGE_PROC_CLASS_BASE + 4)
> #define V4L2_CID_DIGITAL_GAIN (V4L2_CID_IMAGE_PROC_CLASS_BASE + 5)
> +#define V4L2_CID_COMPANDING (V4L2_CID_IMAGE_PROC_CLASS_BASE + 6)
> +enum v4l2_companding {
> + V4L2_COMPANDING_LINEAR = 0,
> + V4L2_COMPANDING_COMPRESS = 1,
> +};
>
> /* DV-class control IDs defined by V4L2 */
> #define V4L2_CID_DV_CLASS_BASE (V4L2_CTRL_CLASS_DV | 0x900)
