Re: [RFC PATCH v6 09/11] media: uapi: Add audio rate controls support

From: Hans Verkuil
Date: Wed Oct 18 2023 - 03:31:12 EST

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On 18/10/2023 09:23, Shengjiu Wang wrote:
> On Wed, Oct 18, 2023 at 10:27 AM Shengjiu Wang <shengjiu.wang@xxxxxxxxx> wrote:
>>
>> On Tue, Oct 17, 2023 at 9:37 PM Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
>>>
>>> On 17/10/2023 15:11, Shengjiu Wang wrote:
>>>> On Mon, Oct 16, 2023 at 9:16 PM Hans Verkuil <hverkuil@xxxxxxxxx> 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@xxxxxxx>
>>>>>> ---
>>>>>> .../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@xxxxxxxxxx/
>>>>>
>>>>> 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.
>>
>
> Currently I think we may define
> V4L2_CID_M2M_AUDIO_SOURCE_RATE
> V4L2_CID_M2M_AUDIO_DEST_RATE

That makes sense.

> V4L2_CID_M2M_AUDIO_ASRC_RATIO_MOD

OK, can you document this control? Just write it down in the reply, I just want
to understand how the integer value you set here is used.

Regards,

Hans

>
> All of them can be V4L2_CTRL_TYPE_INTEGER.
>
> RATIO_MOD was defined in the very beginning version.
> I think it is better to let users calculate this value.
>
> The reason is:
> if we define the offset for source rate and dest rate in
> driver separately, when offset of source rate is set,
> driver don't know if it needs to wait or not the dest rate
> offset, then go to calculate the ratio_mod.
>
> best regards
> wang shengjiu
>
>> 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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In reply to: Shengjiu Wang: "Re: [RFC PATCH v6 09/11] media: uapi: Add audio rate controls support"
Next in thread: Shengjiu Wang: "Re: [RFC PATCH v6 09/11] media: uapi: Add audio rate controls support"
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