From patchwork Tue Jan 21 00:23:48 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andreas Rheinhardt X-Patchwork-Id: 17444 Return-Path: X-Original-To: patchwork@ffaux-bg.ffmpeg.org Delivered-To: patchwork@ffaux-bg.ffmpeg.org Received: from ffbox0-bg.mplayerhq.hu (ffbox0-bg.ffmpeg.org [79.124.17.100]) by ffaux.localdomain (Postfix) with ESMTP id CC31444A911 for ; Tue, 21 Jan 2020 02:30:57 +0200 (EET) Received: from [127.0.1.1] (localhost [127.0.0.1]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTP id ABE8868AF77; Tue, 21 Jan 2020 02:30:57 +0200 (EET) X-Original-To: ffmpeg-devel@ffmpeg.org Delivered-To: ffmpeg-devel@ffmpeg.org Received: from mail-wr1-f67.google.com (mail-wr1-f67.google.com [209.85.221.67]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id 3EDFB68A8A5 for ; Tue, 21 Jan 2020 02:30:51 +0200 (EET) Received: by mail-wr1-f67.google.com with SMTP id t2so1402324wrr.1 for ; Mon, 20 Jan 2020 16:30:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=tLT6zuiJ+0tCF4+uiV0TuW90sdobs+QBgsIeOv/+Irg=; b=jU9HI6HpVFUziYlC9Yohx7cWSsHeT52/t5SMAN1+zFRe8Zr+fHwiPvCwuY1k3hqEg4 4vLSJNW8r8d+GsrytwyfoxGK/VVqmZL3DIdt0ZK7VHaNq8hg6suqjOb+O3nk5pAh5010 ldIy9ytEODQ5KaKTX90q99CRueWiiDIk2ZDeYmz/lpiLWvWuaPAyUojl0zqeoaUo/AlF J16q9HwDTzNzAC/h05IWzsenVNw0TH0DJY2+rpXiop//0tj6Z1EaAK5mVGf8K9B31lBK DSUQ0nhDGBCWMlfXmfXmu50M6S0X3WkRFtO7m1ZgocxJADlmymQNZE4hJBGep98Z2atb Cjtg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=tLT6zuiJ+0tCF4+uiV0TuW90sdobs+QBgsIeOv/+Irg=; b=IFrlgaZ3cz3Bsh8LKSJvwKl2nYxq57BXy7RYnIMteOEzqGfN5w54MRhvut+8XZi8ek BlAsFPdA4nidt8S6jJqG44sdT9fBcIjDRB/ry9ZQYpmT6c6r7Vi8v0SvnTLeQsRw3Yfq kuKFyjoPRbNpqdiEY5HX9yd2+8x6bOSuNmpp/a3YtuQ8RoR3mjrSioAHvdxOeY74+Sxo ImjOOB8SzYkxZAcIJMBK4arytV8NwdDP9YvZgX7VGNF2vvdcvVa1p/ce+MyaWQ/xUBEQ EW7Ns2jv2W8EzqMF/lpST4zw/viJ1rjU26Vy1X9JfIGmaJEnpPG7tSmyqax1zxOTvR1A I0og== X-Gm-Message-State: APjAAAUK4Vgd38KTWFsuNLceBe9LFYoIBqiUdlDQw7ZsRdnMaGYVlcjf 1h+vHR5kWsugNm3nISbMkkbitBP6 X-Google-Smtp-Source: APXvYqyLzotDYw8+trrVYA3ZRhAwy2IMVbUAA3xmQvDpULuTKVef3axvFt1i/gJU2q8Krj5cKdcagA== X-Received: by 2002:a5d:4d0e:: with SMTP id z14mr2030132wrt.208.1579566262527; Mon, 20 Jan 2020 16:24:22 -0800 (PST) Received: from sblaptop.fritz.box ([188.192.139.191]) by smtp.gmail.com with ESMTPSA id t1sm1402102wma.43.2020.01.20.16.24.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jan 2020 16:24:21 -0800 (PST) From: Andreas Rheinhardt To: ffmpeg-devel@ffmpeg.org Date: Tue, 21 Jan 2020 01:23:48 +0100 Message-Id: <20200121002348.16914-2-andreas.rheinhardt@gmail.com> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200121002348.16914-1-andreas.rheinhardt@gmail.com> References: <20200121002348.16914-1-andreas.rheinhardt@gmail.com> MIME-Version: 1.0 Subject: [FFmpeg-devel] [PATCH 2/2] avcodec/j2kenc: Simplify creation of luts X-BeenThere: ffmpeg-devel@ffmpeg.org X-Mailman-Version: 2.1.20 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: Andreas Rheinhardt Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" 1. i * i + (1 << (NMSEDC_FRACBITS - 1)) is always positive (and it doesn't overflow), so one can remove the FFMAX in the computation of lut_nmsedec_sig0. 2. The discriminant of the polynomial i * i - 2^(F + 1) * i + 2^(2 * F) + 2^(F - 1) is negative; hence this polynomial has no real solutions, i.e. its sign doesn't change and is always positive. This allows to remove the FFMAX in the computation of lut_nmsedec_ref0. 3. After that, one sees that the computation of lut_nmsedec_ref0 actually contains lut_nmsedec_sig0. This is obscured by masking the last NMSEDEC_FRACBITS away, but the other summands are multiples of 2^NMSEDEC_FRACBITS and so masking doesn't affect them. Signed-off-by: Andreas Rheinhardt --- Supersedes https://ffmpeg.org/pipermail/ffmpeg-devel/2019-September/250687.html libavcodec/j2kenc.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/libavcodec/j2kenc.c b/libavcodec/j2kenc.c index 38643c9a28..c5c04bc4bf 100644 --- a/libavcodec/j2kenc.c +++ b/libavcodec/j2kenc.c @@ -522,13 +522,13 @@ static void init_luts(void) for (i = 0; i < (1 << NMSEDEC_BITS); i++){ lut_nmsedec_sig[i] = FFMAX((3 * i << (13 - NMSEDEC_FRACBITS)) - (9 << 11), 0); - lut_nmsedec_sig0[i] = FFMAX((i*i + (1<> (NMSEDEC_BITS-2)&2) + 1; lut_nmsedec_ref[i] = FFMAX((a - 2) * (i << (13 - NMSEDEC_FRACBITS)) + (1 << 13) - (a * a << 11), 0); - lut_nmsedec_ref0[i] = FFMAX(((i * i - (i << NMSEDEC_BITS) + (1 << 2 * NMSEDEC_FRACBITS) + (1 << (NMSEDEC_FRACBITS - 1))) & mask) - << 1, 0); + lut_nmsedec_ref0[i] = lut_nmsedec_sig0[i] - (i << (NMSEDEC_BITS + 1)) + + (1 << (2 * NMSEDEC_FRACBITS + 1)); } }