RE: [EXT] Re: [PATCH 01/10] media: Add P012 and P012M video format

[Ming Qian <ming.qian@nxp.com>]

>From: Nicolas Dufresne <nicolas@ndufresne.ca>
>Sent: 2023年2月10日 23:08
>To: Ming Qian <ming.qian@nxp.com>; Hans Verkuil <hverkuil-
>cisco@xs4all.nl>; mchehab@kernel.org; Mirela Rabulea (OSS)
><mirela.rabulea@oss.nxp.com>
>Cc: shawnguo@kernel.org; s.hauer@pengutronix.de; kernel@pengutronix.de;
>festevam@gmail.com; X.H. Bao <xiahong.bao@nxp.com>; dl-linux-imx <linux-
>imx@nxp.com>; linux-media@vger.kernel.org; linux-kernel@vger.kernel.org;
>devicetree@vger.kernel.org; linux-arm-kernel@lists.infradead.org
>Subject: Re: [EXT] Re: [PATCH 01/10] media: Add P012 and P012M video
>format
>
>Caution: EXT Email
>
>Le lundi 30 janvier 2023 à 08:15 +0000, Ming Qian a écrit :
>> > > diff --git a/include/uapi/linux/videodev2.h
>> > > b/include/uapi/linux/videodev2.h index 1befd181a4cc..5448aa3b7858
>> > > 100644
>> > > --- a/include/uapi/linux/videodev2.h
>> > > +++ b/include/uapi/linux/videodev2.h
>> > > @@ -626,12 +626,14 @@ struct v4l2_pix_format {
>> > >   #define V4L2_PIX_FMT_NV24    v4l2_fourcc('N', 'V', '2', '4') /* 24
>> > > Y/CbCr
>> > 4:4:4  */
>> > >   #define V4L2_PIX_FMT_NV42    v4l2_fourcc('N', 'V', '4', '2') /* 24
>> > > Y/CrCb
>> > 4:4:4  */
>> > >   #define V4L2_PIX_FMT_P010    v4l2_fourcc('P', '0', '1', '0') /* 24
>> > > Y/CbCr
>> > 4:2:0 10-bit per component */
>> > > +#define V4L2_PIX_FMT_P012    v4l2_fourcc('P', '0', '1', '2') /* 24
>> > > Y/CbCr
>> > 4:2:0 12-bit per component */
>> > >
>> > >   /* two non contiguous planes - one Y, one Cr + Cb interleaved  */
>> > >   #define V4L2_PIX_FMT_NV12M   v4l2_fourcc('N', 'M', '1', '2') /* 12
>> > > Y/CbCr
>> > 4:2:0  */
>> > >   #define V4L2_PIX_FMT_NV21M   v4l2_fourcc('N', 'M', '2', '1') /* 21
>> > > Y/CrCb
>> > 4:2:0  */
>> > >   #define V4L2_PIX_FMT_NV16M   v4l2_fourcc('N', 'M', '1', '6') /* 16
>> > > Y/CbCr
>> > 4:2:2  */
>> > >   #define V4L2_PIX_FMT_NV61M   v4l2_fourcc('N', 'M', '6', '1') /* 16
>> > > Y/CrCb
>> > 4:2:2  */
>> > > +#define V4L2_PIX_FMT_P012M   v4l2_fourcc('P', 'M', '1', '2') /* 24
>> > > Y/CbCr
>> > 4:2:0 12-bit per component */
>> >
>> > The name of the V4L2_PIX_FMT_ defines in this series are hard to decode.
>> >
>> > In this case is it derived from V4L2_PIX_FMT_P010, which really
>> > should have been named differently, but it's too late now :-(
>> >
>> > So I guess we'll stick with this naming, but it's not obvious what 'P012'
>> > means
>> > without referring to documentation.
>> >
>> > Oh well.
>> >
>> > Regards,
>> >
>> >         Hans
>>
>> Hi Hans,
>>     I'll update the format name, as you know,  the P012 is following
>> the P010, as they are almost the same, and the Y212 comes from
>> gstreamer (GST_VIDEO_FORMAT_Y212_LE), then I did some naming like that.
>>     I'll correct them in v2 patch.
>
>I agree these naming are not obvious. In GStreamer, appart from the _LE part,
>we've had this historical tendency to just stick with Microsoft names when
>they exist. Though Microsoft only define 10 and 16bits (P010/P016, Y210 and
>Y216). In this case, the 12 has is derived from it.
>
>https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flearn.
>microsoft.com%2Fen-us%2Fwindows%2Fwin32%2Fmedfound%2F10-bit-and-
>16-bit-yuv-video-
>formats&data=05%7C01%7Cming.qian%40nxp.com%7C4946d98325684a554d
>a408db0b78aa3a%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C638
>116385106384698%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiL
>CJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sd
>ata=5Z6m1WVxmf6WYXRDZiUuKT9wjx7cOtt%2BRMHzlyT3n5E%3D&reserved=
>0
>
>While P010 is very commonly seen, I don't know if Y210/Y212/Y216 is a great
>idea. It is a 16bit component width version of YUYV, which as we know exist in
>all sort of swizzling. So the Microsoft name will be hard to extend to other
>component order. My argument of keeping it this way though is that it
>matches the other copy of pixel formats definition that exist in Linux, which is
>drm_fourcc.h.
>
>Nicolas

Hi Nicolas,
    Thanks for your comments, I agree with you that the name like Y212 is hard to understand,
I'll correct them to YUYV64_12,  YUV48_12, BGR48_12 and ABGR64_12, but for P012, I prefer to keep it.

Ming