From patchwork Wed Sep 27 13:56:15 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Niklas Haas X-Patchwork-Id: 43988 Delivered-To: ffmpegpatchwork2@gmail.com Received: by 2002:a05:6a20:2a18:b0:15d:8365:d4b8 with SMTP id e24csp2621034pzh; Wed, 27 Sep 2023 06:56:31 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGI2oOtDgktrPePqiNndWP7oKCzNKdWhV+3CnE36zWoz30pS8USEYHZA6oLDX/mJDrVhQ5s X-Received: by 2002:a17:906:208d:b0:9a1:6318:4d39 with SMTP id 13-20020a170906208d00b009a163184d39mr1954583ejq.29.1695822991224; Wed, 27 Sep 2023 06:56:31 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1695822991; cv=none; d=google.com; s=arc-20160816; b=K/3WcZCI87Dkqf9oC18SY0rqDv8Bx35KEv12Hv6AiV3fvrNkYT/VTzfjFHm4SbYnr1 2eDPlleJhlmanCEdIc2ILK8jI8bemo3HeaD+Q+FcXhArzameY2e0Ph/biL+nSBtpXaNs 48LL4uLytO2eMyRniJwR24bkkcnoQfSda3rSdcEh4tSimx9CF1tfz7MsisxFYAIicSi3 PHVspI/b9irXCo5buulZ0oCYY30eEBclA7E+bZQPbZ+KHd54DsfFDbinYnHznzjqlRyd f32BQDxRKebWzz1ew4jW6aLtaPo6eezKDJ5Z6WeEwtYMvKPn672X1Q8GICQnon0++6bv oGCg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=sender:errors-to:content-transfer-encoding:cc:reply-to :list-subscribe:list-help:list-post:list-archive:list-unsubscribe :list-id:precedence:subject:mime-version:message-id:date:to:from :dkim-signature:delivered-to; bh=LTPK8W5ftc2PXMIYvdryJOrGPnOOdxCxPFyCI+Bs9lA=; fh=xmAeKtysnShNOmkhiJmYkS30uw4Fu2hvBJ7qlIwukxQ=; b=z0F92iJpwzUyimkI/akOwjX2f/OiqQ3iLBwX1YUqFREmPCAFCsUy4FneiiruW0zHLI E39uOrF792l+v5r66hbXRWR/SNSnt9FYftpMNz1Lr1xIZ4q5DnPu2UPU0ECKVx2X/xTH pFBNs9g0erD9LLS3r+/g8vo4Gm/ZLVOeBIkXtYiC3sLeX9S5LSKnJ7rN6mwIFCkbeLby yhLfgMhrjN8xbUQT9zNa47TZlr9DiagJsxg8wgBx085Rc/eH+xzrUn0kIBFEMx251/Hm 5UgHRe4P842qS83c/M+l1v0MrhoW9FmWt1fckylykkctbGlxJzu2z+7vYREoMDGHzoV5 pd4w== ARC-Authentication-Results: i=1; mx.google.com; dkim=neutral (body hash did not verify) header.i=@haasn.xyz header.s=mail header.b=kDAAVgiV; spf=pass (google.com: domain of ffmpeg-devel-bounces@ffmpeg.org designates 79.124.17.100 as permitted sender) smtp.mailfrom=ffmpeg-devel-bounces@ffmpeg.org Return-Path: Received: from ffbox0-bg.mplayerhq.hu (ffbox0-bg.ffmpeg.org. [79.124.17.100]) by mx.google.com with ESMTP id bg1-20020a170906a04100b00988d6a7cdefsi14101751ejb.212.2023.09.27.06.56.30; Wed, 27 Sep 2023 06:56:31 -0700 (PDT) Received-SPF: pass (google.com: domain of ffmpeg-devel-bounces@ffmpeg.org designates 79.124.17.100 as permitted sender) client-ip=79.124.17.100; Authentication-Results: mx.google.com; dkim=neutral (body hash did not verify) header.i=@haasn.xyz header.s=mail header.b=kDAAVgiV; spf=pass (google.com: domain of ffmpeg-devel-bounces@ffmpeg.org designates 79.124.17.100 as permitted sender) smtp.mailfrom=ffmpeg-devel-bounces@ffmpeg.org Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id E8F0468CAFA; Wed, 27 Sep 2023 16:56:27 +0300 (EEST) X-Original-To: ffmpeg-devel@ffmpeg.org Delivered-To: ffmpeg-devel@ffmpeg.org Received: from haasn.dev (haasn.dev [78.46.187.166]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id AF4B168CA16 for ; Wed, 27 Sep 2023 16:56:21 +0300 (EEST) Received: from haasn.dev (unknown [10.30.0.2]) by haasn.dev (Postfix) with ESMTP id 35AED41827; Wed, 27 Sep 2023 15:56:21 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=haasn.xyz; s=mail; t=1695822981; bh=yOI/b5jsHtfL6Sxn9PKrsmX/nsGdX6bhq36n5zNaLuc=; h=From:To:Cc:Subject:Date:From; b=kDAAVgiVIqKLEnmY7wK9rq3YqJcEFihgAK8d1kS9irfZS2+kr4bhhJDimsJVmhKN7 pX0b+jglXc6ZrW/zVpQIwTCwQKA96YgfjRf+Asxoa4cQHQ9WTtex+eOhYceBRuhZBg HrI13m/5r1JeQb8fxTGgvx47fmdigxUhIDXVTNb8= From: Niklas Haas To: ffmpeg-devel@ffmpeg.org Date: Wed, 27 Sep 2023 15:56:15 +0200 Message-ID: <20230927135617.33952-1-ffmpeg@haasn.xyz> X-Mailer: git-send-email 2.42.0 MIME-Version: 1.0 Subject: [FFmpeg-devel] [PATCH 1/3] lavc/h274: fix PRNG definition X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FFmpeg development discussions and patches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: FFmpeg development discussions and patches Cc: Niklas Haas Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" X-TUID: d4V8+nE4sZw+ From: Niklas Haas The spec specifies x^31 + x^3 + 1 as the polynomial, but the diagram in Figure 1-1 omits the +1 offset. The initial implementation was based on the diagram, but this is wrong (produces subtly incorrect results). --- libavcodec/h274.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/libavcodec/h274.c b/libavcodec/h274.c index a69f9411429..fc111cdb50d 100644 --- a/libavcodec/h274.c +++ b/libavcodec/h274.c @@ -38,7 +38,7 @@ static void prng_shift(uint32_t *state) { // Primitive polynomial x^31 + x^3 + 1 (modulo 2) uint32_t x = *state; - uint8_t feedback = (x >> 2) ^ (x >> 30); + uint8_t feedback = 1u ^ (x >> 2) ^ (x >> 30); *state = (x << 1) | (feedback & 1u); }