From patchwork Tue Apr 5 07:57:26 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Laurent Pinchart X-Patchwork-Id: 686281 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by demeter1.kernel.org (8.14.4/8.14.3) with ESMTP id p357vhc9002708 for ; Tue, 5 Apr 2011 07:57:43 GMT Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753179Ab1DEH51 (ORCPT ); Tue, 5 Apr 2011 03:57:27 -0400 Received: from perceval.ideasonboard.com ([95.142.166.194]:43020 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752967Ab1DEH5N (ORCPT ); Tue, 5 Apr 2011 03:57:13 -0400 Received: from localhost.localdomain (unknown [91.178.236.143]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id C3C4E35B6B for ; Tue, 5 Apr 2011 07:57:10 +0000 (UTC) From: Laurent Pinchart To: linux-media@vger.kernel.org Subject: [PATCH 04/14] omap3isp: resizer: Improved resizer rsz factor formula Date: Tue, 5 Apr 2011 09:57:26 +0200 Message-Id: <1301990256-6963-5-git-send-email-laurent.pinchart@ideasonboard.com> X-Mailer: git-send-email 1.7.3.4 In-Reply-To: <1301990256-6963-1-git-send-email-laurent.pinchart@ideasonboard.com> References: <1301990256-6963-1-git-send-email-laurent.pinchart@ideasonboard.com> Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org X-Greylist: IP, sender and recipient auto-whitelisted, not delayed by milter-greylist-4.2.6 (demeter1.kernel.org [140.211.167.41]); Tue, 05 Apr 2011 07:57:44 +0000 (UTC) From: Sakari Ailus Round properly the rsz factor so that we get highest rsz so that the input width (or height) is highest possible smaller or equal to what the user asks. Signed-off-by: Sakari Ailus Signed-off-by: Laurent Pinchart --- drivers/media/video/omap3isp/ispresizer.c | 40 +++++++++++++++++++++------- 1 files changed, 30 insertions(+), 10 deletions(-) diff --git a/drivers/media/video/omap3isp/ispresizer.c b/drivers/media/video/omap3isp/ispresizer.c index 40b2db8..70897ce 100644 --- a/drivers/media/video/omap3isp/ispresizer.c +++ b/drivers/media/video/omap3isp/ispresizer.c @@ -714,16 +714,36 @@ static void resizer_print_status(struct isp_res_device *res) * iw and ih are the input width and height after cropping. Those equations need * to be satisfied exactly for the resizer to work correctly. * - * Reverting the equations, we can compute the resizing ratios with + * The equations can't be easily reverted, as the >> 8 operation is not linear. + * In addition, not all input sizes can be achieved for a given output size. To + * get the highest input size lower than or equal to the requested input size, + * we need to compute the highest resizing ratio that satisfies the following + * inequality (taking the 4-tap mode width equation as an example) + * + * iw >= (32 * sph + (ow - 1) * hrsz + 16) >> 8 - 7 + * + * (where iw is the requested input width) which can be rewritten as + * + * iw - 7 >= (32 * sph + (ow - 1) * hrsz + 16) >> 8 + * (iw - 7) << 8 >= 32 * sph + (ow - 1) * hrsz + 16 - b + * ((iw - 7) << 8) + b >= 32 * sph + (ow - 1) * hrsz + 16 + * + * where b is the value of the 8 least significant bits of the right hand side + * expression of the last inequality. The highest resizing ratio value will be + * achieved when b is equal to its maximum value of 255. That resizing ratio + * value will still satisfy the original inequality, as b will disappear when + * the expression will be shifted right by 8. + * + * The reverted the equations thus become * * - 8-phase, 4-tap mode - * hrsz = ((iw - 7) * 256 - 16 - 32 * sph) / (ow - 1) - * vrsz = ((ih - 4) * 256 - 16 - 32 * spv) / (oh - 1) + * hrsz = ((iw - 7) * 256 + 255 - 16 - 32 * sph) / (ow - 1) + * vrsz = ((ih - 4) * 256 + 255 - 16 - 32 * spv) / (oh - 1) * - 4-phase, 7-tap mode - * hrsz = ((iw - 7) * 256 - 32 - 64 * sph) / (ow - 1) - * vrsz = ((ih - 7) * 256 - 32 - 64 * spv) / (oh - 1) + * hrsz = ((iw - 7) * 256 + 255 - 32 - 64 * sph) / (ow - 1) + * vrsz = ((ih - 7) * 256 + 255 - 32 - 64 * spv) / (oh - 1) * - * The ratios are integer values, and must be rounded down to ensure that the + * The ratios are integer values, and are rounded down to ensure that the * cropped input size is not bigger than the uncropped input size. * * As the number of phases/taps, used to select the correct equations to compute @@ -799,10 +819,10 @@ static void resizer_calc_ratios(struct isp_res_device *res, max_height = min_t(unsigned int, max_height, MAX_OUT_HEIGHT); output->height = clamp(output->height, min_height, max_height); - ratio->vert = ((input->height - 4) * 256 - 16 - 32 * spv) + ratio->vert = ((input->height - 4) * 256 + 255 - 16 - 32 * spv) / (output->height - 1); if (ratio->vert > MID_RESIZE_VALUE) - ratio->vert = ((input->height - 7) * 256 - 32 - 64 * spv) + ratio->vert = ((input->height - 7) * 256 + 255 - 32 - 64 * spv) / (output->height - 1); ratio->vert = clamp_t(unsigned int, ratio->vert, MIN_RESIZE_VALUE, MAX_RESIZE_VALUE); @@ -870,10 +890,10 @@ static void resizer_calc_ratios(struct isp_res_device *res, max_width & ~(width_alignment - 1)); output->width = ALIGN(output->width, width_alignment); - ratio->horz = ((input->width - 7) * 256 - 16 - 32 * sph) + ratio->horz = ((input->width - 7) * 256 + 255 - 16 - 32 * sph) / (output->width - 1); if (ratio->horz > MID_RESIZE_VALUE) - ratio->horz = ((input->width - 7) * 256 - 32 - 64 * sph) + ratio->horz = ((input->width - 7) * 256 + 255 - 32 - 64 * sph) / (output->width - 1); ratio->horz = clamp_t(unsigned int, ratio->horz, MIN_RESIZE_VALUE, MAX_RESIZE_VALUE);