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Date: Fri, 5 Oct 2018 08:09:24 -0300
From: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
To: Ezequiel Garcia <ezequiel@collabora.com>
Cc: linux-media@vger.kernel.org, devicetree@vger.kernel.org,
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        Hans Verkuil <hans.verkuil@cisco.com>, kernel@collabora.com,
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        Miouyouyou <myy@miouyouyou.fr>,
        Shunqian Zheng <zhengsq@rock-chips.com>
Subject: Re: [PATCH v7 4/6] media: Add JPEG_RAW format
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Em Thu,  4 Oct 2018 21:12:24 -0300
Ezequiel Garcia <ezequiel@collabora.com> escreveu:

> From: Shunqian Zheng <zhengsq@rock-chips.com>
> 
> Add V4L2_PIX_FMT_JPEG_RAW format that does not contain
> JPEG header in the output frame.
> 
> Signed-off-by: Shunqian Zheng <zhengsq@rock-chips.com>
> Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
> ---
>  Documentation/media/uapi/v4l/pixfmt-compressed.rst | 9 +++++++++
>  drivers/media/v4l2-core/v4l2-ioctl.c               | 1 +
>  include/uapi/linux/videodev2.h                     | 1 +
>  3 files changed, 11 insertions(+)
> 
> diff --git a/Documentation/media/uapi/v4l/pixfmt-compressed.rst b/Documentation/media/uapi/v4l/pixfmt-compressed.rst
> index ba0f6c49d9bf..ad73076276ec 100644
> --- a/Documentation/media/uapi/v4l/pixfmt-compressed.rst
> +++ b/Documentation/media/uapi/v4l/pixfmt-compressed.rst
> @@ -23,6 +23,15 @@ Compressed Formats
>        - 'JPEG'
>        - TBD. See also :ref:`VIDIOC_G_JPEGCOMP <VIDIOC_G_JPEGCOMP>`,
>  	:ref:`VIDIOC_S_JPEGCOMP <VIDIOC_G_JPEGCOMP>`.
> +    * .. _V4L2-PIX-FMT-JPEG-RAW:
> +
> +      - ``V4L2_PIX_FMT_JPEG_RAW``
> +      - 'Raw JPEG'
> +      - Raw JPEG bitstream, containing a compressed payload. This format
> +        contains an image scan, i.e. without any metadata or headers.
> +        The user is expected to set the needed metadata such as
> +        quantization and entropy encoding tables, via ``V4L2_CID_JPEG``
> +        controls, see :ref:`jpeg-control-id`.

IMO, it is not very clear when someone should use V4L2_CID_JPEG or
V4L2_PIX_FMT_JPEG_RAW. Some drivers do add a JPEG header internally.

Also, if we're now starting to accept headerless JPEG images, you should
very patch libv4l as well, in order to accept this new format.

Regards,

Thanks,
Mauro