Message-ID: <CAA+D8AMa9tpMq08XsUuAtV0DLWbLOwsfYjd30NJ3OBezkTs5YA@mail.gmail.com>
Date:   Wed, 18 Oct 2023 10:27:04 +0800
From:   Shengjiu Wang <shengjiu.wang@...il.com>
To:     Hans Verkuil <hverkuil@...all.nl>
Cc:     Shengjiu Wang <shengjiu.wang@....com>, sakari.ailus@....fi,
        tfiga@...omium.org, m.szyprowski@...sung.com, mchehab@...nel.org,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xiubo.Lee@...il.com, festevam@...il.com, nicoleotsuka@...il.com,
        lgirdwood@...il.com, broonie@...nel.org, perex@...ex.cz,
        tiwai@...e.com, alsa-devel@...a-project.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [RFC PATCH v6 09/11] media: uapi: Add audio rate controls support

On Tue, Oct 17, 2023 at 9:37 PM Hans Verkuil <hverkuil@...all.nl> wrote:
>
> On 17/10/2023 15:11, Shengjiu Wang wrote:
> > On Mon, Oct 16, 2023 at 9:16 PM Hans Verkuil <hverkuil@...all.nl> wrote:
> >>
> >> Hi Shengjiu,
> >>
> >> On 13/10/2023 10:31, Shengjiu Wang wrote:
> >>> Fixed point controls are used by the user to configure
> >>> the audio sample rate to driver.
> >>>
> >>> Add V4L2_CID_ASRC_SOURCE_RATE and V4L2_CID_ASRC_DEST_RATE
> >>> new IDs for ASRC rate control.
> >>>
> >>> Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
> >>> ---
> >>>  .../userspace-api/media/v4l/common.rst        |  1 +
> >>>  .../media/v4l/ext-ctrls-fixed-point.rst       | 36 +++++++++++++++++++
> >>>  .../media/v4l/vidioc-g-ext-ctrls.rst          |  4 +++
> >>>  .../media/v4l/vidioc-queryctrl.rst            |  7 ++++
> >>>  .../media/videodev2.h.rst.exceptions          |  1 +
> >>>  drivers/media/v4l2-core/v4l2-ctrls-core.c     |  5 +++
> >>>  drivers/media/v4l2-core/v4l2-ctrls-defs.c     |  4 +++
> >>>  include/media/v4l2-ctrls.h                    |  2 ++
> >>>  include/uapi/linux/v4l2-controls.h            | 13 +++++++
> >>>  include/uapi/linux/videodev2.h                |  3 ++
> >>>  10 files changed, 76 insertions(+)
> >>>  create mode 100644 Documentation/userspace-api/media/v4l/ext-ctrls-fixed-point.rst
> >>>
> >>> diff --git a/Documentation/userspace-api/media/v4l/common.rst b/Documentation/userspace-api/media/v4l/common.rst
> >>> index ea0435182e44..35707edffb13 100644
> >>> --- a/Documentation/userspace-api/media/v4l/common.rst
> >>> +++ b/Documentation/userspace-api/media/v4l/common.rst
> >>> @@ -52,6 +52,7 @@ applicable to all devices.
> >>>      ext-ctrls-fm-rx
> >>>      ext-ctrls-detect
> >>>      ext-ctrls-colorimetry
> >>> +    ext-ctrls-fixed-point
> >>
> >> Rename this to ext-ctrls-audio-m2m.
> >>
> >>>      fourcc
> >>>      format
> >>>      planar-apis
> >>> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-fixed-point.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-fixed-point.rst
> >>> new file mode 100644
> >>> index 000000000000..2ef6e250580c
> >>> --- /dev/null
> >>> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-fixed-point.rst
> >>> @@ -0,0 +1,36 @@
> >>> +.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
> >>> +
> >>> +.. _fixed-point-controls:
> >>> +
> >>> +***************************
> >>> +Fixed Point Control Reference
> >>
> >> This is for audio controls. "Fixed Point" is just the type, and it doesn't make
> >> sense to group fixed point controls. But it does make sense to group the audio
> >> controls.
> >>
> >> V4L2 controls can be grouped into classes. Basically it is a way to put controls
> >> into categories, and for each category there is also a control that gives a
> >> description of the class (see 2.15.15 in
> >> https://linuxtv.org/downloads/v4l-dvb-apis-new/driver-api/v4l2-controls.html#introduction)
> >>
> >> If you use e.g. 'v4l2-ctl -l' to list all the controls, then you will see that
> >> they are grouped based on what class of control they are.
> >>
> >> So I think it would be a good idea to create a new control class for M2M audio controls,
> >> instead of just adding them to the catch-all 'User Controls' class.
> >>
> >> Search e.g. for V4L2_CTRL_CLASS_COLORIMETRY and V4L2_CID_COLORIMETRY_CLASS to see how
> >> it is done.
> >>
> >> M2M_AUDIO would probably be a good name for the class.
> >>
> >>> +***************************
> >>> +
> >>> +These controls are intended to support an asynchronous sample
> >>> +rate converter.
> >>
> >> Add ' (ASRC).' at the end to indicate the common abbreviation for
> >> that.
> >>
> >>> +
> >>> +.. _v4l2-audio-asrc:
> >>> +
> >>> +``V4L2_CID_ASRC_SOURCE_RATE``
> >>> +    sets the resampler source rate.
> >>> +
> >>> +``V4L2_CID_ASRC_DEST_RATE``
> >>> +    sets the resampler destination rate.
> >>
> >> Document the unit (Hz) for these two controls.
> >>
> >>> +
> >>> +.. c:type:: v4l2_ctrl_fixed_point
> >>> +
> >>> +.. cssclass:: longtable
> >>> +
> >>> +.. tabularcolumns:: |p{1.5cm}|p{5.8cm}|p{10.0cm}|
> >>> +
> >>> +.. flat-table:: struct v4l2_ctrl_fixed_point
> >>> +    :header-rows:  0
> >>> +    :stub-columns: 0
> >>> +    :widths:       1 1 2
> >>> +
> >>> +    * - __u32
> >>
> >> Hmm, shouldn't this be __s32?
> >>
> >>> +      - ``integer``
> >>> +      - integer part of fixed point value.
> >>> +    * - __s32
> >>
> >> and this __u32?
> >>
> >> You want to be able to use this generic type as a signed value.
> >>
> >>> +      - ``fractional``
> >>> +      - fractional part of fixed point value, which is Q31.
> >>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst b/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
> >>> index f9f73530a6be..1811dabf5c74 100644
> >>> --- a/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
> >>> +++ b/Documentation/userspace-api/media/v4l/vidioc-g-ext-ctrls.rst
> >>> @@ -295,6 +295,10 @@ still cause this situation.
> >>>        - ``p_av1_film_grain``
> >>>        - A pointer to a struct :c:type:`v4l2_ctrl_av1_film_grain`. Valid if this control is
> >>>          of type ``V4L2_CTRL_TYPE_AV1_FILM_GRAIN``.
> >>> +    * - struct :c:type:`v4l2_ctrl_fixed_point` *
> >>> +      - ``p_fixed_point``
> >>> +      - A pointer to a struct :c:type:`v4l2_ctrl_fixed_point`. Valid if this control is
> >>> +        of type ``V4L2_CTRL_TYPE_FIXED_POINT``.
> >>>      * - void *
> >>>        - ``ptr``
> >>>        - A pointer to a compound type which can be an N-dimensional array
> >>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
> >>> index 4d38acafe8e1..9285f4f39eed 100644
> >>> --- a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
> >>> +++ b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst
> >>> @@ -549,6 +549,13 @@ See also the examples in :ref:`control`.
> >>>        - n/a
> >>>        - A struct :c:type:`v4l2_ctrl_av1_film_grain`, containing AV1 Film Grain
> >>>          parameters for stateless video decoders.
> >>> +    * - ``V4L2_CTRL_TYPE_FIXED_POINT``
> >>> +      - n/a
> >>> +      - n/a
> >>> +      - n/a
> >>> +      - A struct :c:type:`v4l2_ctrl_fixed_point`, containing parameter which has
> >>> +        integer part and fractional part, i.e. audio sample rate.
> >>> +
> >>>
> >>>  .. raw:: latex
> >>>
> >>> diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> >>> index e61152bb80d1..2faa5a2015eb 100644
> >>> --- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> >>> +++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
> >>> @@ -167,6 +167,7 @@ replace symbol V4L2_CTRL_TYPE_AV1_SEQUENCE :c:type:`v4l2_ctrl_type`
> >>>  replace symbol V4L2_CTRL_TYPE_AV1_TILE_GROUP_ENTRY :c:type:`v4l2_ctrl_type`
> >>>  replace symbol V4L2_CTRL_TYPE_AV1_FRAME :c:type:`v4l2_ctrl_type`
> >>>  replace symbol V4L2_CTRL_TYPE_AV1_FILM_GRAIN :c:type:`v4l2_ctrl_type`
> >>> +replace symbol V4L2_CTRL_TYPE_FIXED_POINT :c:type:`v4l2_ctrl_type`
> >>>
> >>>  # V4L2 capability defines
> >>>  replace define V4L2_CAP_VIDEO_CAPTURE device-capabilities
> >>> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-core.c b/drivers/media/v4l2-core/v4l2-ctrls-core.c
> >>> index a662fb60f73f..7a616ac91059 100644
> >>> --- a/drivers/media/v4l2-core/v4l2-ctrls-core.c
> >>> +++ b/drivers/media/v4l2-core/v4l2-ctrls-core.c
> >>> @@ -1168,6 +1168,8 @@ static int std_validate_compound(const struct v4l2_ctrl *ctrl, u32 idx,
> >>>               if (!area->width || !area->height)
> >>>                       return -EINVAL;
> >>>               break;
> >>> +     case V4L2_CTRL_TYPE_FIXED_POINT:
> >>> +             break;
> >>
> >> Hmm, this would need this patch 'v4l2-ctrls: add support for V4L2_CTRL_WHICH_MIN/MAX_VAL':
> >>
> >> https://patchwork.linuxtv.org/project/linux-media/patch/20231010022136.1504015-7-yunkec@google.com/
> >>
> >> since min and max values are perfectly fine for a fixed point value.
> >>
> >> Even a step value (currently not supported in that patch) would make sense.
> >>
> >> But I wonder if we couldn't simplify this: instead of creating a v4l2_ctrl_fixed_point,
> >> why not represent the fixed point value as a Q31.32. Then the standard
> >> minimum/maximum/step values can be used, and it acts like a regular V4L2_TYPE_INTEGER64.
> >>
> >> Except that both userspace and drivers need to multiply it with 2^-32 to get the actual
> >> value.
> >>
> >> So in enum v4l2_ctrl_type add:
> >>
> >>         V4L2_CTRL_TYPE_FIXED_POINT = 10,
> >>
> >> (10, because it is no longer a compound type).
> >
> > Seems we don't need V4L2_CTRL_TYPE_FIXED_POINT, just use V4L2_TYPE_INTEGER64?
> >
> > The reason I use the 'integer' and 'fractional' is that I want
> > 'integer' to be the normal sample
> > rate, for example 48kHz.  The 'fractional' is the difference with
> > normal sample rate.
> >
> > For example, the rate = 47998.12345.  so integer = 48000,  fractional= -1.87655.
> >
> > So if we use s64 for rate, then in driver need to convert the rate to
> > the closed normal
> > sample rate + fractional.
>
> That wasn't what the documentation said :-)
>
> So this is really two controls: one for the 'normal sample rate' (whatever 'normal'
> means in this context) and the offset to the actual sample rate.
>
> Presumably the 'normal' sample rate is set once, while the offset changes
> regularly.
>
> But why do you need the 'normal' sample rate? With audio resampling I assume
> you resample from one rate to another, so why do you need a third 'normal'
> rate?
>

'Normal' rate is used to select the prefilter table.

Best regards
Wang Shengjiu

> Regards,
>
>         Hans
>
> >
> > best regards
> > wang shengjiu
> >
> >>
> >>>
> >>>       default:
> >>>               return -EINVAL;
> >>> @@ -1868,6 +1870,9 @@ static struct v4l2_ctrl *v4l2_ctrl_new(struct v4l2_ctrl_handler *hdl,
> >>>       case V4L2_CTRL_TYPE_AREA:
> >>>               elem_size = sizeof(struct v4l2_area);
> >>>               break;
> >>> +     case V4L2_CTRL_TYPE_FIXED_POINT:
> >>> +             elem_size = sizeof(struct v4l2_ctrl_fixed_point);
> >>> +             break;
> >>>       default:
> >>>               if (type < V4L2_CTRL_COMPOUND_TYPES)
> >>>                       elem_size = sizeof(s32);
> >>> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> >>> index 8696eb1cdd61..d8f232df6b6a 100644
> >>> --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> >>> +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> >>> @@ -1602,6 +1602,10 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
> >>>       case V4L2_CID_COLORIMETRY_HDR10_MASTERING_DISPLAY:
> >>>               *type = V4L2_CTRL_TYPE_HDR10_MASTERING_DISPLAY;
> >>>               break;
> >>> +     case V4L2_CID_ASRC_SOURCE_RATE:
> >>> +     case V4L2_CID_ASRC_DEST_RATE:
> >>> +             *type = V4L2_CTRL_TYPE_FIXED_POINT;
> >>> +             break;
> >>>       default:
> >>>               *type = V4L2_CTRL_TYPE_INTEGER;
> >>>               break;
> >>> diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
> >>> index 59679a42b3e7..645e4cccafc7 100644
> >>> --- a/include/media/v4l2-ctrls.h
> >>> +++ b/include/media/v4l2-ctrls.h
> >>> @@ -56,6 +56,7 @@ struct video_device;
> >>>   * @p_av1_tile_group_entry:  Pointer to an AV1 tile group entry structure.
> >>>   * @p_av1_frame:             Pointer to an AV1 frame structure.
> >>>   * @p_av1_film_grain:                Pointer to an AV1 film grain structure.
> >>> + * @p_fixed_point:           Pointer to a struct v4l2_ctrl_fixed_point.
> >>>   * @p:                               Pointer to a compound value.
> >>>   * @p_const:                 Pointer to a constant compound value.
> >>>   */
> >>> @@ -89,6 +90,7 @@ union v4l2_ctrl_ptr {
> >>>       struct v4l2_ctrl_av1_tile_group_entry *p_av1_tile_group_entry;
> >>>       struct v4l2_ctrl_av1_frame *p_av1_frame;
> >>>       struct v4l2_ctrl_av1_film_grain *p_av1_film_grain;
> >>> +     struct v4l2_ctrl_fixed_point *p_fixed_point;
> >>>       void *p;
> >>>       const void *p_const;
> >>>  };
> >>> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
> >>> index c3604a0a3e30..91096259e3ea 100644
> >>> --- a/include/uapi/linux/v4l2-controls.h
> >>> +++ b/include/uapi/linux/v4l2-controls.h
> >>> @@ -112,6 +112,8 @@ enum v4l2_colorfx {
> >>>
> >>>  /* last CID + 1 */
> >>>  #define V4L2_CID_LASTP1                         (V4L2_CID_BASE+44)
> >>> +#define V4L2_CID_ASRC_SOURCE_RATE            (V4L2_CID_BASE + 45)
> >>> +#define V4L2_CID_ASRC_DEST_RATE                      (V4L2_CID_BASE + 46)
> >>
> >> This patch needs to be split in three parts:
> >>
> >> 1) Add the new M2M_AUDIO control class,
> >> 2) Add the new V4L2_CTRL_TYPE_FIXED_POINT type,
> >> 3) Add the new controls.
> >>
> >> These are all independent changes, so separating them makes it easier to
> >> review.
> >>
> >>>
> >>>  /* USER-class private control IDs */
> >>>
> >>> @@ -3488,4 +3490,15 @@ struct v4l2_ctrl_av1_film_grain {
> >>>  #define V4L2_CID_MPEG_MFC51_BASE        V4L2_CID_CODEC_MFC51_BASE
> >>>  #endif
> >>>
> >>> +/**
> >>> + * struct v4l2_ctrl_fixed_point - fixed point parameter.
> >>> + *
> >>> + * @rate_integer: integer part of fixed point value.
> >>> + * @rate_fractional: fractional part of fixed point value
> >>> + */
> >>> +struct v4l2_ctrl_fixed_point {
> >>> +     __u32 integer;
> >>
> >> __s32?
> >>
> >>> +     __u32 fractional;
> >>> +};
> >>> +
> >>>  #endif
> >>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> >>> index 2ac7b989394c..3ef32c09c2fa 100644
> >>> --- a/include/uapi/linux/videodev2.h
> >>> +++ b/include/uapi/linux/videodev2.h
> >>> @@ -1888,6 +1888,7 @@ struct v4l2_ext_control {
> >>>               struct v4l2_ctrl_av1_tile_group_entry __user *p_av1_tile_group_entry;
> >>>               struct v4l2_ctrl_av1_frame __user *p_av1_frame;
> >>>               struct v4l2_ctrl_av1_film_grain __user *p_av1_film_grain;
> >>> +             struct v4l2_ctrl_fixed_point __user *p_fixed_point;
> >>>               void __user *ptr;
> >>>       };
> >>>  } __attribute__ ((packed));
> >>> @@ -1966,6 +1967,8 @@ enum v4l2_ctrl_type {
> >>>       V4L2_CTRL_TYPE_AV1_TILE_GROUP_ENTRY = 0x281,
> >>>       V4L2_CTRL_TYPE_AV1_FRAME            = 0x282,
> >>>       V4L2_CTRL_TYPE_AV1_FILM_GRAIN       = 0x283,
> >>> +
> >>> +     V4L2_CTRL_TYPE_FIXED_POINT          = 0x290,
> >>>  };
> >>>
> >>>  /*  Used in the VIDIOC_QUERYCTRL ioctl for querying controls */
> >>
> >> Regards,
> >>
> >>         Hans
>

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