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SubjectRe: [PATCH] v4l: Add source change event for colorimetry
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On 10/13/20 4:40 PM, Tomasz Figa wrote:
> On Tue, Oct 13, 2020 at 11:03 AM Stanimir Varbanov
> <stanimir.varbanov@linaro.org> wrote:
>>
>> Hi,
>>
>> On 7/2/20 2:52 PM, Stanimir Varbanov wrote:
>>> Hi,
>>>
>>> Once we have this event there is still open question how the client will
>>> know the data buffer on which the new colorspace is valid/applied.
>>>
>>> The options could be:
>>> * a new buffer flag and
>>> * some information in the v4l2_event structure.
>>>
>>> Thoughts?
>>
>> Kindly ping.
>>
>
> The event itself sounds good to me, but how do we know which buffer is
> the first to have the new colorimetry?

I think Hans have a very good idea to have width/height and colorspace
specifiers in v4l2_ext_buffer [1].

[1] https://lkml.org/lkml/2020/9/9/531

>
> Best regards,
> Tomasz
>
>>>
>>> On 7/2/20 1:00 PM, Stanimir Varbanov wrote:
>>>> This event indicate that the source colorspace is changed
>>>> during run-time. The client has to retrieve the new colorspace
>>>> identifiers by getting the format (G_FMT).
>>>>
>>>> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
>>>> ---
>>>> .../userspace-api/media/v4l/vidioc-dqevent.rst | 11 ++++++++++-
>>>> .../userspace-api/media/videodev2.h.rst.exceptions | 1 +
>>>> include/uapi/linux/videodev2.h | 1 +
>>>> 3 files changed, 12 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/Documentation/userspace-api/media/v4l/vidioc-dqevent.rst b/Documentation/userspace-api/media/v4l/vidioc-dqevent.rst
>>>> index a9a176d5256d..3f69c753db58 100644
>>>> --- a/Documentation/userspace-api/media/v4l/vidioc-dqevent.rst
>>>> +++ b/Documentation/userspace-api/media/v4l/vidioc-dqevent.rst
>>>> @@ -381,7 +381,16 @@ call.
>>>> that many Video Capture devices are not able to recover from a temporary
>>>> loss of signal and so restarting streaming I/O is required in order for
>>>> the hardware to synchronize to the video signal.
>>>> -
>>>> + * - ``V4L2_EVENT_SRC_CH_COLORIMETRY``
>>>> + - 0x0002
>>>> + - This event gets triggered when a colorspace change is detected at
>>>> + an input. By colorspace change here we include also changes in the
>>>> + colorspace specifiers (transfer function, Y'CbCr encoding and
>>>> + quantization). This event can come from an input or from video decoder.
>>>> + Once the event has been send to the client the driver has to update
>>>> + the colorspace specifiers internally so that they could be retrieved by
>>>> + client. In that case queue re-negotiation is not needed as this change
>>>> + only reflects on the interpretation of the data.
>>>>
>>>> Return Value
>>>> ============
>>>> diff --git a/Documentation/userspace-api/media/videodev2.h.rst.exceptions b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>>>> index ca05e4e126b2..54fc21af852d 100644
>>>> --- a/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>>>> +++ b/Documentation/userspace-api/media/videodev2.h.rst.exceptions
>>>> @@ -492,6 +492,7 @@ replace define V4L2_EVENT_CTRL_CH_FLAGS ctrl-changes-flags
>>>> replace define V4L2_EVENT_CTRL_CH_RANGE ctrl-changes-flags
>>>>
>>>> replace define V4L2_EVENT_SRC_CH_RESOLUTION src-changes-flags
>>>> +replace define V4L2_EVENT_SRC_CH_COLORIMETRY src-changes-flags
>>>>
>>>> replace define V4L2_EVENT_MD_FL_HAVE_FRAME_SEQ :c:type:`v4l2_event_motion_det`
>>>>
>>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>>>> index 303805438814..b5838bc4e3a3 100644
>>>> --- a/include/uapi/linux/videodev2.h
>>>> +++ b/include/uapi/linux/videodev2.h
>>>> @@ -2351,6 +2351,7 @@ struct v4l2_event_frame_sync {
>>>> };
>>>>
>>>> #define V4L2_EVENT_SRC_CH_RESOLUTION (1 << 0)
>>>> +#define V4L2_EVENT_SRC_CH_COLORIMETRY (1 << 1)
>>>>
>>>> struct v4l2_event_src_change {
>>>> __u32 changes;
>>>>
>>>
>>
>> --
>> regards,
>> Stan

--
regards,
Stan

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