[{"id":4015,"web_url":"https://patchwork.libcamera.org/comment/4015/","msgid":"","date":"2020-03-14T11:14:12","subject":"Re: [libcamera-devel] [PATCH 7/8] libcamera: v4l2_videodevice: Map\n\tV4L2_PIX_FMT_GREY to DRM FourCC","submitter":{"id":30,"url":"https://patchwork.libcamera.org/api/people/30/","name":"Nicolas Dufresne","email":"nicolas@ndufresne.ca"},"content":"Le samedi 14 mars 2020 à 01:38 +0200, Laurent Pinchart a écrit :\n> DRM has a format for 8-bit greyscale data, DRM_FORMAT_R8. Despite the\n> 'R' name, which comes from GL/Vulkan to mean single-channel data, the\n> format maps to greyscale for display. We can thus map it to\n> V4L2_PIX_FMT_GREY.\n\nThe mapping looks fine to me, but may lead to surprising result in\nabsence of colorimetry support. Most YCbCr 4:0:0 will be limited range,\nwhile on the GFX side, most of R8 usage will be full range. Just be\naware.\n\nNicolas\n\n> \n> Signed-off-by: Laurent Pinchart \n> ---\n> src/libcamera/v4l2_videodevice.cpp | 9 ++++++++-\n> 1 file changed, 8 insertions(+), 1 deletion(-)\n> \n> diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp\n> index f68b67b33293..f89bf2ff781e 100644\n> --- a/src/libcamera/v4l2_videodevice.cpp\n> +++ b/src/libcamera/v4l2_videodevice.cpp\n> @@ -1473,12 +1473,15 @@ PixelFormat V4L2VideoDevice::toPixelFormat(uint32_t v4l2Fourcc)\n> \tcase V4L2_PIX_FMT_NV21M:\n> \t\treturn DRM_FORMAT_NV21;\n> \n> +\t/* Greyscale formats. */\n> +\tcase V4L2_PIX_FMT_GREY:\n> +\t\treturn DRM_FORMAT_R8;\n> +\n> \t/* Compressed formats. */\n> \tcase V4L2_PIX_FMT_MJPEG:\n> \t\treturn DRM_FORMAT_MJPEG;\n> \n> \t/* V4L2 formats not yet supported by DRM. */\n> -\tcase V4L2_PIX_FMT_GREY:\n> \tdefault:\n> \t\t/*\n> \t\t * \\todo We can't use LOG() in a static method of a Loggable\n> @@ -1557,6 +1560,10 @@ uint32_t V4L2VideoDevice::toV4L2Fourcc(PixelFormat pixelFormat, bool multiplanar\n> \tcase DRM_FORMAT_NV21:\n> \t\treturn V4L2_PIX_FMT_NV21;\n> \n> +\t/* Greyscale formats. */\n> +\tcase DRM_FORMAT_R8:\n> +\t\treturn V4L2_PIX_FMT_GREY;\n> +\n> \t/* Compressed formats. */\n> \tcase DRM_FORMAT_MJPEG:\n> \t\treturn V4L2_PIX_FMT_MJPEG;","headers":{"Return-Path":"","Received":["from mail-qk1-x741.google.com (mail-qk1-x741.google.com\n\t[IPv6:2607:f8b0:4864:20::741])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 572216041D\n\tfor ;\n\tSat, 14 Mar 2020 12:14:15 +0100 (CET)","by mail-qk1-x741.google.com with SMTP id f3so17437968qkh.1\n\tfor ;\n\tSat, 14 Mar 2020 04:14:15 -0700 (PDT)","from skullcanyon ([192.222.193.21])\n\tby smtp.gmail.com with ESMTPSA id\n\tu26sm6607077qku.97.2020.03.14.04.14.12\n\t(version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256);\n\tSat, 14 Mar 2020 04:14:13 -0700 (PDT)"],"DKIM-Signature":"v=1; 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\n\tSat, 14 Mar 2020 04:14:14 -0700 (PDT)","Message-ID":"","From":"Nicolas Dufresne ","To":"Laurent Pinchart , \n\tlibcamera-devel@lists.libcamera.org","Cc":"Martijn Braam , Mickael GUENE , \n\tBenjamin GAIGNARD ","Date":"Sat, 14 Mar 2020 07:14:12 -0400","In-Reply-To":"<20200313233856.25202-8-laurent.pinchart@ideasonboard.com>","References":"<20200313233856.25202-1-laurent.pinchart@ideasonboard.com>\n\t<20200313233856.25202-8-laurent.pinchart@ideasonboard.com>","Content-Type":"text/plain; charset=\"UTF-8\"","User-Agent":"Evolution 3.34.4 (3.34.4-1.fc31) ","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit","Subject":"Re: [libcamera-devel] [PATCH 7/8] libcamera: v4l2_videodevice: Map\n\tV4L2_PIX_FMT_GREY to DRM FourCC","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","X-List-Received-Date":"Sat, 14 Mar 2020 11:14:15 -0000"}},{"id":4016,"web_url":"https://patchwork.libcamera.org/comment/4016/","msgid":"<20200314114732.GB5320@pendragon.ideasonboard.com>","date":"2020-03-14T11:47:32","subject":"Re: [libcamera-devel] [PATCH 7/8] libcamera: v4l2_videodevice: Map\n\tV4L2_PIX_FMT_GREY to DRM FourCC","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"Hi Nicolas,\n\nOn Sat, Mar 14, 2020 at 07:14:12AM -0400, Nicolas Dufresne wrote:\n> Le samedi 14 mars 2020 à 01:38 +0200, Laurent Pinchart a écrit :\n> > DRM has a format for 8-bit greyscale data, DRM_FORMAT_R8. Despite the\n> > 'R' name, which comes from GL/Vulkan to mean single-channel data, the\n> > format maps to greyscale for display. We can thus map it to\n> > V4L2_PIX_FMT_GREY.\n> \n> The mapping looks fine to me, but may lead to surprising result in\n> absence of colorimetry support. Most YCbCr 4:0:0 will be limited range,\n> while on the GFX side, most of R8 usage will be full range. Just be\n> aware.\n\nThanks for the comment. In the specific case I'm trying to support, data\ncomes from a sensor that doesn't have a Bayer filter, so it's really\nfull range greyscale (it's actually 10 bits scaled down to 8 bits). In\nthe general case, we need to convey colorimetry information, I agree\nwith you, and that's something that can't be conveyed just through a\n4CC, we will need a dedicated API.\n\n> > Signed-off-by: Laurent Pinchart \n> > ---\n> > src/libcamera/v4l2_videodevice.cpp | 9 ++++++++-\n> > 1 file changed, 8 insertions(+), 1 deletion(-)\n> > \n> > diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp\n> > index f68b67b33293..f89bf2ff781e 100644\n> > --- a/src/libcamera/v4l2_videodevice.cpp\n> > +++ b/src/libcamera/v4l2_videodevice.cpp\n> > @@ -1473,12 +1473,15 @@ PixelFormat V4L2VideoDevice::toPixelFormat(uint32_t v4l2Fourcc)\n> > \tcase V4L2_PIX_FMT_NV21M:\n> > \t\treturn DRM_FORMAT_NV21;\n> > \n> > +\t/* Greyscale formats. */\n> > +\tcase V4L2_PIX_FMT_GREY:\n> > +\t\treturn DRM_FORMAT_R8;\n> > +\n> > \t/* Compressed formats. */\n> > \tcase V4L2_PIX_FMT_MJPEG:\n> > \t\treturn DRM_FORMAT_MJPEG;\n> > \n> > \t/* V4L2 formats not yet supported by DRM. */\n> > -\tcase V4L2_PIX_FMT_GREY:\n> > \tdefault:\n> > \t\t/*\n> > \t\t * \\todo We can't use LOG() in a static method of a Loggable\n> > @@ -1557,6 +1560,10 @@ uint32_t V4L2VideoDevice::toV4L2Fourcc(PixelFormat pixelFormat, bool multiplanar\n> > \tcase DRM_FORMAT_NV21:\n> > \t\treturn V4L2_PIX_FMT_NV21;\n> > \n> > +\t/* Greyscale formats. */\n> > +\tcase DRM_FORMAT_R8:\n> > +\t\treturn V4L2_PIX_FMT_GREY;\n> > +\n> > \t/* Compressed formats. */\n> > \tcase DRM_FORMAT_MJPEG:\n> > \t\treturn V4L2_PIX_FMT_MJPEG;","headers":{"Return-Path":"","Received":["from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 890F06041D\n\tfor ;\n\tSat, 14 Mar 2020 12:47:36 +0100 (CET)","from pendragon.ideasonboard.com (81-175-216-236.bb.dnainternet.fi\n\t[81.175.216.236])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 02AB4B22;\n\tSat, 14 Mar 2020 12:47:35 +0100 (CET)"],"DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1584186456;\n\tbh=TTsXQLlNSbDvEeuETY72qOoN5QTlt8BqOl6wc/lRfUo=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=ZMNhX19H7Ox1AamZWtF3xmnLrhudlNyJuQpcKgSewUa2/V8UWQ8iYwPpBF1blKdTb\n\tJx7QaMEhZiBEaUby8jQvHiCFUYdUxacpJf1KMAdWDiizDLAy5QWK7tH9AuvVXLx/Cb\n\t5u3HZzSqR1/QISLi+owMQ+LTTFLtjcQWfXOnKOpc=","Date":"Sat, 14 Mar 2020 13:47:32 +0200","From":"Laurent Pinchart ","To":"Nicolas Dufresne ","Cc":"libcamera-devel@lists.libcamera.org, Martijn Braam , \n\tMickael GUENE ,\n\tBenjamin GAIGNARD ","Message-ID":"<20200314114732.GB5320@pendragon.ideasonboard.com>","References":"<20200313233856.25202-1-laurent.pinchart@ideasonboard.com>\n\t<20200313233856.25202-8-laurent.pinchart@ideasonboard.com>\n\t","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","Content-Transfer-Encoding":"8bit","In-Reply-To":"","User-Agent":"Mutt/1.10.1 (2018-07-13)","Subject":"Re: [libcamera-devel] [PATCH 7/8] libcamera: v4l2_videodevice: Map\n\tV4L2_PIX_FMT_GREY to DRM FourCC","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","X-List-Received-Date":"Sat, 14 Mar 2020 11:47:36 -0000"}}]