linux-kernel - Re: [RFC PATCH v7 11/13] media: uapi: Add audio rate controls support

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Message-ID: <7929b801-63a4-4b30-9da7-e080e38a7e40@xs4all.nl>
Date:   Wed, 25 Oct 2023 12:47:07 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     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,
        shengjiu.wang@...il.com, 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 v7 11/13] media: uapi: Add audio rate controls support

On 20/10/2023 11:30, Shengjiu Wang wrote:
> Add V4L2_CID_M2M_AUDIO_SOURCE_RATE and V4L2_CID_M2M_AUDIO_DEST_RATE
> new IDs for rate control.
> 
> Add V4L2_CID_M2M_AUDIO_SOURCE_RATE_OFFSET and
> V4L2_CID_M2M_AUDIO_DEST_RATE_OFFSET for clock drift.
> 
> Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
> ---
>  .../media/v4l/ext-ctrls-audio-m2m.rst          | 18 ++++++++++++++++++
>  drivers/media/v4l2-core/v4l2-ctrls-defs.c      | 12 ++++++++++++
>  include/uapi/linux/v4l2-controls.h             |  5 +++++
>  3 files changed, 35 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-audio-m2m.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-audio-m2m.rst
> index 82d2ecedbfee..e6972a2d3b17 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-audio-m2m.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-audio-m2m.rst
> @@ -19,3 +19,21 @@ Audio M2M Control IDs
>      The Audio M2M class descriptor. Calling
>      :ref:`VIDIOC_QUERYCTRL` for this control will
>      return a description of this control class.
> +
> +.. _v4l2-audio-asrc:
> +
> +``V4L2_CID_M2M_AUDIO_SOURCE_RATE``

Add ' (integer menu)' after the name.

> +    Sets the audio source rate, unit is (Hz)

(Hz) -> Hz.

General question: is 'rate' good enough or should it be 'sample rate'?

> +
> +``V4L2_CID_M2M_AUDIO_DEST_RATE``
> +    Sets the audio destination rate, unit is (Hz)

Ditto here.

> +
> +``V4L2_CID_M2M_AUDIO_SOURCE_RATE_OFFSET``

Add ' (fixed point)' after the name.

> +    Sets the offset for audio source rate, unit is (Hz).

for -> from the

(Hz) -> Hz

> +    Offset expresses the drift of clock if there is. It is
> +    equal to real rate minus ideal rate.

How about:

The offset compensates for any clock drift. The actual source audio
rate is the ideal source audio rate from ``V4L2_CID_M2M_AUDIO_SOURCE_RATE``
plus this fixed point offset.

> +
> +``V4L2_CID_M2M_AUDIO_DEST_RATE_OFFSET``
> +    Sets the offset for audio destination rate, unit is (Hz)
> +    Offset expresses the drift of clock if there is. It is
> +    equal to real rate minus ideal rate.

Same changes as for V4L2_CID_M2M_AUDIO_SOURCE_RATE_OFFSET.

> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> index 2a85ea3dc92f..b695cbdd1f6e 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> @@ -1245,6 +1245,10 @@ const char *v4l2_ctrl_get_name(u32 id)
>  
>  	/* Audio M2M controls */
>  	case V4L2_CID_M2M_AUDIO_CLASS:  return "Audio M2M Controls";
> +	case V4L2_CID_M2M_AUDIO_SOURCE_RATE:	return "Audio Source Sample Rate";
> +	case V4L2_CID_M2M_AUDIO_DEST_RATE:	return "Audio Dest Sample Rate";
> +	case V4L2_CID_M2M_AUDIO_SOURCE_RATE_OFFSET:	return "Audio Source Sample Rate Offset";
> +	case V4L2_CID_M2M_AUDIO_DEST_RATE_OFFSET:	return "Audio Dest Sample Rate Offset";

Related to my question above: "Sample Rate" or just "Rate"? Whatever we pick, it should
be consistent.

>  	default:
>  		return NULL;
>  	}
> @@ -1606,6 +1610,14 @@ 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_M2M_AUDIO_SOURCE_RATE:
> +	case V4L2_CID_M2M_AUDIO_DEST_RATE:
> +		*type = V4L2_CTRL_TYPE_INTEGER_MENU;
> +		break;
> +	case V4L2_CID_M2M_AUDIO_SOURCE_RATE_OFFSET:
> +	case V4L2_CID_M2M_AUDIO_DEST_RATE_OFFSET:
> +		*type = V4L2_CTRL_TYPE_FIXED_POINT;
> +		break;
>  	default:
>  		*type = V4L2_CTRL_TYPE_INTEGER;
>  		break;
> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
> index eb0f0a76f867..d433c6f0b533 100644
> --- a/include/uapi/linux/v4l2-controls.h
> +++ b/include/uapi/linux/v4l2-controls.h
> @@ -3498,4 +3498,9 @@ struct v4l2_ctrl_av1_film_grain {
>  #define V4L2_CID_M2M_AUDIO_CLASS_BASE  (V4L2_CTRL_CLASS_M2M_AUDIO | 0x900)
>  #define V4L2_CID_M2M_AUDIO_CLASS       (V4L2_CTRL_CLASS_M2M_AUDIO | 1)
>  
> +#define V4L2_CID_M2M_AUDIO_SOURCE_RATE	(V4L2_CID_M2M_AUDIO_CLASS_BASE + 0)
> +#define V4L2_CID_M2M_AUDIO_DEST_RATE	(V4L2_CID_M2M_AUDIO_CLASS_BASE + 1)
> +#define V4L2_CID_M2M_AUDIO_SOURCE_RATE_OFFSET	(V4L2_CID_M2M_AUDIO_CLASS_BASE + 2)
> +#define V4L2_CID_M2M_AUDIO_DEST_RATE_OFFSET	(V4L2_CID_M2M_AUDIO_CLASS_BASE + 3)
> +
>  #endif

Regards,

	Hans