linux-kernel - Re: [PATCH 1/2] v4l2-ctrl: Add decoder conceal color control

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Date:   Thu, 25 Feb 2021 12:12:20 +0200
From:   Stanimir Varbanov <stanimir.varbanov@...aro.org>
To:     Hans Verkuil <hverkuil-cisco@...all.nl>,
        Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 1/2] v4l2-ctrl: Add decoder conceal color control



On 2/16/21 10:58 AM, Hans Verkuil wrote:
> On 16/02/2021 09:56, Stanimir Varbanov wrote:
>>
>>
>> On 2/15/21 1:57 PM, Hans Verkuil wrote:
>>> On 15/02/2021 12:32, Stanimir Varbanov wrote:
>>>>
>>>>
>>>> On 2/9/21 1:05 PM, Hans Verkuil wrote:
>>>>> On 09/02/2021 10:45, Stanimir Varbanov wrote:
>>>>>> Add decoder v4l2 control to set conceal color.
>>>>>>
>>>>>> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@...aro.org>
>>>>>> ---
>>>>>>  .../media/v4l/ext-ctrls-codec.rst             | 20 +++++++++++++++++++
>>>>>>  drivers/media/v4l2-core/v4l2-ctrls.c          |  9 +++++++++
>>>>>>  include/uapi/linux/v4l2-controls.h            |  1 +
>>>>>>  3 files changed, 30 insertions(+)
>>>>>>
>>>>>> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>>>>>> index 00944e97d638..994650052333 100644
>>>>>> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>>>>>> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>>>>>> @@ -674,6 +674,26 @@ enum v4l2_mpeg_video_frame_skip_mode -
>>>>>>      is currently displayed (decoded). This value is reset to 0 whenever
>>>>>>      the decoder is started.
>>>>>>  
>>>>>> +``V4L2_CID_MPEG_VIDEO_DEC_CONCEAL_COLOR (integer64)``
>>>>>> +    This control sets conceal color in YUV color space. It describes the
>>>>>> +    client preference of error conceal color in case of error where
>>>>>> +    reference frame is missing. The decoder would paint the reference
>>>>>> +    buffer with preferred color and use it for future decoding.
>>>>>> +    Applicable to decoders.
>>>>>
>>>>> You should mention explicitly that this is using 16-bit color components
>>>>> and expects Limited Range.
>>>>
>>>> I don't want to limit the client to Limited range only. I'll mention in
>>>> the description that both ranges are valid.
>>>
>>> OK, but then you need to describe what the color format depends on. See more
>>> below.
>>>
>>>>
>>>>>
>>>>>> +
>>>>>> +.. flat-table::
>>>>>> +    :header-rows:  0
>>>>>> +    :stub-columns: 0
>>>>>> +
>>>>>> +    * - Bit 0:15
>>>>>> +      - Y luminance
>>>>>> +    * - Bit 16:31
>>>>>> +      - Cb chrominance
>>>>>> +    * - Bit 32:47
>>>>>> +      - Cr chrominance
>>>>>> +    * - Bit 48:63
>>>>>> +      - Must be zero
>>>>>> +
>>
>> The table how the bits are spread into int64.
>>
>>>>>>  ``V4L2_CID_MPEG_VIDEO_DECODER_SLICE_INTERFACE (boolean)``
>>>>>>      If enabled the decoder expects to receive a single slice per buffer,
>>>>>>      otherwise the decoder expects a single frame in per buffer.
>>>>>> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
>>>>>> index 016cf6204cbb..a3b9d28a00b7 100644
>>>>>> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
>>>>>> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
>>>>>> @@ -945,6 +945,7 @@ const char *v4l2_ctrl_get_name(u32 id)
>>>>>>  	case V4L2_CID_MPEG_VIDEO_VBV_SIZE:			return "VBV Buffer Size";
>>>>>>  	case V4L2_CID_MPEG_VIDEO_DEC_PTS:			return "Video Decoder PTS";
>>>>>>  	case V4L2_CID_MPEG_VIDEO_DEC_FRAME:			return "Video Decoder Frame Count";
>>>>>> +	case V4L2_CID_MPEG_VIDEO_DEC_CONCEAL_COLOR:		return "Video Decoder Conceal Color";
>>>>>>  	case V4L2_CID_MPEG_VIDEO_VBV_DELAY:			return "Initial Delay for VBV Control";
>>>>>>  	case V4L2_CID_MPEG_VIDEO_MV_H_SEARCH_RANGE:		return "Horizontal MV Search Range";
>>>>>>  	case V4L2_CID_MPEG_VIDEO_MV_V_SEARCH_RANGE:		return "Vertical MV Search Range";
>>>>>> @@ -1430,6 +1431,14 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
>>>>>>  		*max = 0x7fffffffffffffffLL;
>>>>>>  		*step = 1;
>>>>>>  		break;
>>>>>> +	case V4L2_CID_MPEG_VIDEO_DEC_CONCEAL_COLOR:
>>>>>> +		*type = V4L2_CTRL_TYPE_INTEGER64;
>>>>>> +		*min = 0;
>>>>>> +		/* default for 8bit black, luma is 16, chroma is 128 */
>>>>>
>>>>> Since this is 16 bit the actual default luma value for black is 4096 and for chroma use
>>>>> 32768 (i.e. both values are times 256).
>>>>
>>>> If we follow this for pixel format with 10bit per channel we have to
>>>> multiply by 64?
>>>
>>> No, you multiply by 4. 12 bit depth will multiple by 16, and 16 bit depth by 256.
>>>
>>> But how do you format this? Using bits 29-0? Or use 9-0 for one color component,
>>> 25-16 for another and 41-32 for the last component?
>>
>> I described this in the table above:
>>
>> Bit  0:15 - Y luminance
>> Bit 16:31 - Cb chrominance
>> Bit 32:47 - Cr chrominance
>> Bit 48:63 - Must be zero
>>
>> So depending on the bit depth of the current pixel format:
>>
>>  8bit - 0:7  Y', 16:23 Cb, 32:39 Cr
>> 10bit - 0:9  Y', 16:25 Cb, 32:41 Cr
>> 12bit - 0:11 Y', 16:27 Cb, 32:43 Cr

^^^^

> 
> Apologies, I missed that table!

Hans, do you want me to update with the above ^^^^ components bits or
something else?

-- 
regards,
Stan