[{"id":37201,"web_url":"https://patchwork.libcamera.org/comment/37201/","msgid":"<85ecpb1it3.fsf@mzamazal-thinkpadp1gen7.tpbc.csb>","date":"2025-12-03T19:12:08","subject":"Re: [PATCH v6 11/24] libcamera: shaders: Fix input sampling when\n\twidth != stride","submitter":{"id":177,"url":"https://patchwork.libcamera.org/api/people/177/","name":"Milan Zamazal","email":"mzamazal@redhat.com"},"content":"Bryan O'Donoghue writes:\n\n> From: Hans de Goede \n>\n> When bayer_unpacked.vert is calculating the center and x/yCoord values\n> stride != width is taken into account for x/yCoord deltas since it is taken\n> into account by debayer_egl when setting the x part of tex_step uniform.\n>\n> But it is not taken into account for the center.x which is just directly\n> copied from textureIn, leading to the input width sampling covering\n> the entire input stride instead of just covering the input width.\n>\n> Use the existing and currently unused stride_factor uniform to pass\n> the width/stride ratio and correct center.x for this. This fixes\n> the misrendering seen on x86 laptops which is caused by the CSI2 receiver\n> there requiring a stride which is a multiple of 32 often leading to\n> stride != width.\n>\n> Signed-off-by: Hans de Goede \n> Signed-off-by: Bryan O'Donoghue \n> ---\n> src/libcamera/shaders/bayer_unpacked.vert | 6 ++++--\n> 1 file changed, 4 insertions(+), 2 deletions(-)\n>\n> diff --git a/src/libcamera/shaders/bayer_unpacked.vert b/src/libcamera/shaders/bayer_unpacked.vert\n> index fb5109eee..423dde0fa 100644\n> --- a/src/libcamera/shaders/bayer_unpacked.vert\n> +++ b/src/libcamera/shaders/bayer_unpacked.vert\n> @@ -21,7 +21,7 @@ attribute vec2 textureIn;\n> \n> uniform mat4 proj_matrix;\n> \n> -uniform vec2 tex_size;\t/* The texture size in pixels */\n> +uniform vec2 tex_size; /* The texture size in pixels */\n> uniform vec2 tex_step;\n> \n> /** Pixel position of the first red pixel in the */\n> @@ -40,8 +40,10 @@ varying vec4 xCoord;\n> /** of the adjacent pixels.*/\n> varying vec4 yCoord;\n> \n> +uniform float stride_factor;\n\nWould it be nicer to put this next to the other uniform declarations\nabove?\n\nAnyway, with or without that change:\n\nReviewed-by: Milan Zamazal \n\n> +\n> void main(void) {\n> - center.xy = textureIn;\n> + center.xy = vec2(textureIn.x * stride_factor, textureIn.y);\n> center.zw = textureIn * tex_size + tex_bayer_first_red;\n> \n> xCoord = center.x + vec4(-2.0 * tex_step.x,","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id CDBE4C3257\n\tfor ;\n\tWed, 3 Dec 2025 19:12:17 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 017E06101E;\n\tWed, 3 Dec 2025 20:12:17 +0100 (CET)","from us-smtp-delivery-124.mimecast.com\n\t(us-smtp-delivery-124.mimecast.com [170.10.129.124])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id CC1A4609D8\n\tfor ;\n\tWed, 3 Dec 2025 20:12:14 +0100 (CET)","from mail-wr1-f71.google.com (mail-wr1-f71.google.com\n\t[209.85.221.71]) by relay.mimecast.com with ESMTP with STARTTLS\n\t(version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id\n\tus-mta-61-3Awb1bY_MyuJsj730xnzLw-1; Wed, 03 Dec 2025 14:12:11 -0500","by mail-wr1-f71.google.com with SMTP id\n\tffacd0b85a97d-42e2e3c3e1aso67773f8f.1\n\tfor ;\n\tWed, 03 Dec 2025 11:12:10 -0800 (PST)","from mzamazal-thinkpadp1gen7.tpbc.csb\n\t(ip-77-48-47-2.net.vodafone.cz. 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