From patchwork Sun Jul 3 10:26:35 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Anton Khirnov X-Patchwork-Id: 36628 Delivered-To: ffmpegpatchwork2@gmail.com Received: by 2002:a05:6a20:8b27:b0:88:1bbf:7fd2 with SMTP id l39csp2138919pzh; Sun, 3 Jul 2022 03:28:29 -0700 (PDT) X-Google-Smtp-Source: AGRyM1ugQybm3HPjFLdStsha9GXaDLjf4LRvjMqROpsGeZePv2seTj35pyxyozd88X58/jcIZRZ2 X-Received: by 2002:a17:907:94d1:b0:726:efcd:ca4 with SMTP id dn17-20020a17090794d100b00726efcd0ca4mr23434929ejc.148.1656844109764; Sun, 03 Jul 2022 03:28:29 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1656844109; cv=none; d=google.com; s=arc-20160816; b=jBkyhQy1TB9nCvQaDdiAQjXCBJWNDVGT1EbgYOELALNdCNyEUJQ/lDTZbO7n0JBZ0N PU3N38aVIQgmqrH71eIGiNfPDh0R8tKbg4XLXRG+Q+RFToi2kgjwXswE0gKrN8PlHrQX 1ImlHIryaI1RDfLs06JdId2O4TURKfhuSQzTdH4Cp7Ku2a0LBhEXj0JQWWg8INlstvrO EiMnjuwMqbgV/24Qy2dHfWAqB14g54J5iMD06d4ydZ3Ww/os+cqR8gBTSfkgVzl1PhXS C9elvi2riGrzdLpS+EIMV8CMTBSuK6E7i/MJwbYuna7rB4VHDC8S0GsZYZq2AI1vPG94 DqFw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=sender:errors-to:content-transfer-encoding:reply-to:list-subscribe :list-help:list-post:list-archive:list-unsubscribe:list-id :precedence:subject:mime-version:references:in-reply-to:message-id :date:to:from:delivered-to; bh=mZc8rFAoeeqYyLM38tRQ3Z2DkUbgVEjl593LcNTf+fQ=; b=Zjr+Fq8rhq6S5fNqC9Lbd23mfde08ZUQebREULD27EIxajXSb1BxqzgwBIyfhxjOy+ HriWdOMiANlzw4xOfejc8YfExIvQtONc887m/6SHuEbGCwu82FUj6fA9cHzp30caXbq8 iur/IEJw6v3kgrxPnQOtQ9n3uKmcR0OC4aRq3z9agQ78R7qrlUDZg/3rVjjn2X2Xw8Jv uwLr1KZC06scX470cY3Qg3T8uTAi6WBJtTY6RuQiSOipQYmqMIUpsFIIuvIsnFrgcjj4 4rwN1Db8tyeZxSSLXhvXZxupj2XYfIw5lWgbU4AfnAry+YsptrLO+89pSBpIpFVkJHic Y9ig== ARC-Authentication-Results: i=1; mx.google.com; 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 cq4-20020a056402220400b0043a41583a03si593509edb.71.2022.07.03.03.28.29; Sun, 03 Jul 2022 03:28:29 -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; 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 8EEA368B9C5; Sun, 3 Jul 2022 13:28:20 +0300 (EEST) X-Original-To: ffmpeg-devel@ffmpeg.org Delivered-To: ffmpeg-devel@ffmpeg.org Received: from mail0.khirnov.net (red.khirnov.net [176.97.15.12]) by ffbox0-bg.mplayerhq.hu (Postfix) with ESMTPS id 3949768B98E for ; Sun, 3 Jul 2022 13:28:13 +0300 (EEST) Received: from localhost (localhost [IPv6:::1]) by mail0.khirnov.net (Postfix) with ESMTP id 85FC42400F5 for ; Sun, 3 Jul 2022 12:28:12 +0200 (CEST) Received: from mail0.khirnov.net ([IPv6:::1]) by localhost (mail0.khirnov.net [IPv6:::1]) (amavisd-new, port 10024) with ESMTP id vITsvEreZgOL for ; Sun, 3 Jul 2022 12:28:10 +0200 (CEST) Received: from libav.khirnov.net (libav.khirnov.net [IPv6:2a00:c500:561:201::7]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "libav.khirnov.net", Issuer "smtp.khirnov.net SMTP CA" (verified OK)) by mail0.khirnov.net (Postfix) with ESMTPS id 9A143240179 for ; Sun, 3 Jul 2022 12:28:10 +0200 (CEST) Received: by libav.khirnov.net (Postfix, from userid 1000) id C95583A0909; Sun, 3 Jul 2022 12:28:10 +0200 (CEST) From: Anton Khirnov To: ffmpeg-devel@ffmpeg.org Date: Sun, 3 Jul 2022 12:26:35 +0200 Message-Id: <20220703102636.32523-2-anton@khirnov.net> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220703102636.32523-1-anton@khirnov.net> References: <20220703102636.32523-1-anton@khirnov.net> MIME-Version: 1.0 Subject: [FFmpeg-devel] [PATCH 2/3] lavc: add standalone cached bitstream reader 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 Errors-To: ffmpeg-devel-bounces@ffmpeg.org Sender: "ffmpeg-devel" X-TUID: 94K6HkisM2VI From: Alexandra Hájková The cached bitstream reader was originally written by Alexandra Hájková for Libav, with significant input from Kostya Shishkov and Luca Barbato. It was then committed to FFmpeg in ca079b09549, by merging it with the implementation of the current bitstream reader. This merge makes the code of get_bits.h significantly harder to read, since it now contains two different bitstream readers interleaved with #ifdefs. Additionally, the code was committed without proper authorship attribution. This commit re-adds the cached bitstream reader as a standalone header, as it was originally developed. It will be made useful in following commits. Integration by Anton Khirnov. Signed-off-by: Anton Khirnov --- Addressed all review comments by Andreas. Resending only the bistream reader for now, since any significant changes to it mean that the templatization patch needs to be basically redone from scratch. Will send the rest after this is approved. --- libavcodec/bitstream.h | 540 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 540 insertions(+) create mode 100644 libavcodec/bitstream.h diff --git a/libavcodec/bitstream.h b/libavcodec/bitstream.h new file mode 100644 index 0000000000..53bcdf4643 --- /dev/null +++ b/libavcodec/bitstream.h @@ -0,0 +1,540 @@ +/* + * Copyright (c) 2016 Alexandra Hájková + * + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * FFmpeg is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +/** + * @file + * bitstream reader API header. + */ + +#ifndef AVCODEC_BITSTREAM_H +#define AVCODEC_BITSTREAM_H + +#include + +#include "config.h" + +#include "libavutil/avassert.h" +#include "libavutil/common.h" +#include "libavutil/intreadwrite.h" +#include "libavutil/log.h" + +#include "mathops.h" +#include "vlc.h" + +#ifndef UNCHECKED_BITSTREAM_READER +#define UNCHECKED_BITSTREAM_READER !CONFIG_SAFE_BITSTREAM_READER +#endif + +typedef struct BitstreamContext { + uint64_t bits; // stores bits read from the buffer + const uint8_t *buffer, *buffer_end; + const uint8_t *ptr; // pointer to the position inside a buffer + unsigned bits_left; // number of bits left in bits field + unsigned size_in_bits; +} BitstreamContext; + +/** + * @return + * - 0 on successful refill + * - a negative number when bitstream end is hit + * + * Always succeeds when UNCHECKED_BITSTREAM_READER is enabled. + */ +static inline int bits_priv_refill_64(BitstreamContext *bc) +{ +#if !UNCHECKED_BITSTREAM_READER + if (bc->ptr >= bc->buffer_end) + return -1; +#endif + +#ifdef BITSTREAM_READER_LE + bc->bits = AV_RL64(bc->ptr); +#else + bc->bits = AV_RB64(bc->ptr); +#endif + bc->ptr += 8; + bc->bits_left = 64; + + return 0; +} + +/** + * @return + * - 0 on successful refill + * - a negative number when bitstream end is hit + * + * Always succeeds when UNCHECKED_BITSTREAM_READER is enabled. + */ +static inline int bits_priv_refill_32(BitstreamContext *bc) +{ +#if !UNCHECKED_BITSTREAM_READER + if (bc->ptr >= bc->buffer_end) + return -1; +#endif + +#ifdef BITSTREAM_READER_LE + bc->bits = (uint64_t)AV_RL32(bc->ptr) << bc->bits_left | bc->bits; +#else + bc->bits = bc->bits | (uint64_t)AV_RB32(bc->ptr) << (32 - bc->bits_left); +#endif + bc->ptr += 4; + bc->bits_left += 32; + + return 0; +} + +/** + * Initialize BitstreamContext. + * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes + * larger than the actual read bits because some optimized bitstream + * readers read 32 or 64 bits at once and could read over the end + * @param bit_size the size of the buffer in bits + * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow. + */ +static inline int bits_init(BitstreamContext *bc, const uint8_t *buffer, + unsigned int bit_size) +{ + unsigned int buffer_size; + + if (bit_size > INT_MAX - 7 || !buffer) { + bc->buffer = NULL; + bc->ptr = NULL; + bc->bits_left = 0; + return AVERROR_INVALIDDATA; + } + + buffer_size = (bit_size + 7) >> 3; + + bc->buffer = buffer; + bc->buffer_end = buffer + buffer_size; + bc->ptr = bc->buffer; + bc->size_in_bits = bit_size; + bc->bits_left = 0; + bc->bits = 0; + + bits_priv_refill_64(bc); + + return 0; +} + +/** + * Initialize BitstreamContext. + * @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes + * larger than the actual read bits because some optimized bitstream + * readers read 32 or 64 bits at once and could read over the end + * @param byte_size the size of the buffer in bytes + * @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow + */ +static inline int bits_init8(BitstreamContext *bc, const uint8_t *buffer, + unsigned int byte_size) +{ + if (byte_size > INT_MAX / 8) + return AVERROR_INVALIDDATA; + return bits_init(bc, buffer, byte_size * 8); +} + +/** + * Return number of bits already read. + */ +static inline int bits_tell(const BitstreamContext *bc) +{ + return (bc->ptr - bc->buffer) * 8 - bc->bits_left; +} + +/** + * Return buffer size in bits. + */ +static inline int bits_size(const BitstreamContext *bc) +{ + return bc->size_in_bits; +} + +/** + * Return the number of the bits left in a buffer. + */ +static inline int bits_left(const BitstreamContext *bc) +{ + return (bc->buffer - bc->ptr) * 8 + bc->size_in_bits + bc->bits_left; +} + +static inline uint64_t bits_priv_val_get(BitstreamContext *bc, unsigned int n) +{ + uint64_t ret; + + av_assert2(n > 0 && n < 64); + +#ifdef BITSTREAM_READER_LE + ret = bc->bits & ((UINT64_C(1) << n) - 1); + bc->bits >>= n; +#else + ret = bc->bits >> (64 - n); + bc->bits <<= n; +#endif + bc->bits_left -= n; + + return ret; +} + +/** + * Return one bit from the buffer. + */ +static inline unsigned int bits_read_bit(BitstreamContext *bc) +{ + if (!bc->bits_left) + bits_priv_refill_64(bc); + + return bits_priv_val_get(bc, 1); +} + +/** + * Return n bits from the buffer, n has to be in the 1-32 range. + * May be faster than bits_read() when n is not a compile-time constant and is + * known to be non-zero; + */ +static inline uint32_t bits_read_nz(BitstreamContext *bc, unsigned int n) +{ + av_assert2(n > 0 && n <= 32); + + if (n > bc->bits_left) { + if (bits_priv_refill_32(bc) < 0) + bc->bits_left = n; + } + + return bits_priv_val_get(bc, n); +} + +/** + * Return n bits from the buffer, n has to be in the 0-32 range. + */ +static inline uint32_t bits_read(BitstreamContext *bc, unsigned int n) +{ + av_assert2(n <= 32); + + if (!n) + return 0; + + return bits_read_nz(bc, n); +} + +/** + * Return n bits from the buffer, n has to be in the 0-63 range. + */ +static inline uint64_t bits_read_63(BitstreamContext *bc, unsigned int n) +{ + uint64_t ret = 0; + unsigned left = 0; + + av_assert2(n <= 63); + + if (!n) + return 0; + + if (n > bc->bits_left) { + left = bc->bits_left; + n -= left; + + if (left) + ret = bits_priv_val_get(bc, left); + + if (bits_priv_refill_64(bc) < 0) + bc->bits_left = n; + + } + +#ifdef BITSTREAM_READER_LE + ret = bits_priv_val_get(bc, n) << left | ret; +#else + ret = bits_priv_val_get(bc, n) | ret << n; +#endif + + return ret; +} + +/** + * Return n bits from the buffer, n has to be in the 0-64 range. + */ +static inline uint64_t bits_read_64(BitstreamContext *bc, unsigned int n) +{ + av_assert2(n <= 64); + + if (n == 64) { + uint64_t ret = bits_read(bc, 32); +#ifdef BITSTREAM_READER_LE + return ret | ((uint64_t)bits_read(bc, 32) << 32); +#else + return (ret << 32) | bits_read(bc, 32); +#endif + } + return bits_read_63(bc, n); +} + +/** + * Return n bits from the buffer as a signed integer. + * n has to be in the 0-32 range. + */ +static inline int32_t bits_read_signed(BitstreamContext *bc, unsigned int n) +{ + return sign_extend(bits_read(bc, n), n); +} + +static inline unsigned int bits_priv_val_show(BitstreamContext *bc, unsigned int n) +{ +#ifdef BITSTREAM_READER_LE + return bc->bits & ((UINT64_C(1) << n) - 1); +#else + return bc->bits >> (64 - n); +#endif +} + +/** + * Return n bits from the buffer but do not change the buffer state. + * n has to be in the 0-32 range. + */ +static inline unsigned int bits_peek(BitstreamContext *bc, unsigned int n) +{ + av_assert2(n <= 32); + + if (n > bc->bits_left) + bits_priv_refill_32(bc); + + return bits_priv_val_show(bc, n); +} + +/** + * Return n bits from the buffer as a signed integer, + * do not change the buffer state. + * n has to be in the 0-32 range. + */ +static inline int bits_peek_signed(BitstreamContext *bc, unsigned int n) +{ + return sign_extend(bits_peek(bc, n), n); +} + +static inline void bits_priv_skip_remaining(BitstreamContext *bc, unsigned int n) +{ +#ifdef BITSTREAM_READER_LE + bc->bits >>= n; +#else + bc->bits <<= n; +#endif + bc->bits_left -= n; +} + +/** + * Skip n bits in the buffer. + */ +static inline void bits_skip(BitstreamContext *bc, unsigned int n) +{ + if (n < bc->bits_left) + bits_priv_skip_remaining(bc, n); + else { + n -= bc->bits_left; + bc->bits = 0; + bc->bits_left = 0; + + if (n >= 64) { + unsigned int skip = n / 8; + + n -= skip * 8; + bc->ptr += skip; + } + bits_priv_refill_64(bc); + if (n) + bits_priv_skip_remaining(bc, n); + } +} + +/** + * Seek to the given bit position. + */ +static inline void bits_seek(BitstreamContext *bc, unsigned pos) +{ + bc->ptr = bc->buffer; + bc->bits = 0; + bc->bits_left = 0; + + bits_skip(bc, pos); +} + +/** + * Skip bits to a byte boundary. + */ +static inline const uint8_t *bits_align(BitstreamContext *bc) +{ + unsigned int n = -bits_tell(bc) & 7; + if (n) + bits_skip(bc, n); + return bc->buffer + (bits_tell(bc) >> 3); +} + +/** + * Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB). + * If MSB not set it is negative. + * @param n length in bits + */ +static inline int bits_read_xbits(BitstreamContext *bc, unsigned int n) +{ + int32_t cache = bits_peek(bc, 32); + int sign = ~cache >> 31; + bits_priv_skip_remaining(bc, n); + + return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign; +} + +/** + * Return decoded truncated unary code for the values 0, 1, 2. + */ +static inline int bits_decode012(BitstreamContext *bc) +{ + if (!bits_read_bit(bc)) + return 0; + else + return bits_read_bit(bc) + 1; +} + +/** + * Return decoded truncated unary code for the values 2, 1, 0. + */ +static inline int bits_decode210(BitstreamContext *bc) +{ + if (bits_read_bit(bc)) + return 0; + else + return 2 - bits_read_bit(bc); +} + +/* Read sign bit and flip the sign of the provided value accordingly. */ +static inline int bits_apply_sign(BitstreamContext *bc, int val) +{ + int sign = bits_read_signed(bc, 1); + return (val ^ sign) - sign; +} + +static inline int bits_skip_1stop_8data(BitstreamContext *s) +{ + if (bits_left(s) <= 0) + return AVERROR_INVALIDDATA; + + while (bits_read(s, 1)) { + bits_skip(s, 8); + if (bits_left(s) <= 0) + return AVERROR_INVALIDDATA; + } + + return 0; +} + +/* Unget up to 32 bits. */ +static inline void bits_unget(BitstreamContext *bc, uint64_t value, + unsigned amount) +{ + unsigned cache_size = sizeof(bc->bits) * 8; + + av_assert2(amount <= 32); + + if (bc->bits_left + amount > cache_size) { + bc->bits_left -= 4 * 8; + bc->ptr -= 4; + } + +#ifdef BITSTREAM_READER_LE + bc->bits = (bc->bits << amount) | value; +#else + bc->bits = (bc->bits >> amount) | (value << (cache_size - amount)); +#endif + bc->bits_left += amount; +} + +/** + * Return the LUT element for the given bitstream configuration. + */ +static inline int bits_priv_set_idx(BitstreamContext *bc, int code, int *n, int *nb_bits, + const VLCElem *table) +{ + unsigned idx; + + *nb_bits = -*n; + idx = bits_peek(bc, *nb_bits) + code; + *n = table[idx].len; + + return table[idx].sym; +} + +/** + * Parse a vlc code. + * @param bits is the number of bits which will be read at once, must be + * identical to nb_bits in init_vlc() + * @param max_depth is the number of times bits bits must be read to completely + * read the longest vlc code + * = (max_vlc_length + bits - 1) / bits + * If the vlc code is invalid and max_depth=1, then no bits will be removed. + * If the vlc code is invalid and max_depth>1, then the number of bits removed + * is undefined. + */ +static inline int bits_read_vlc(BitstreamContext *bc, const VLCElem *table, + int bits, int max_depth) +{ + int nb_bits; + unsigned idx = bits_peek(bc, bits); + int code = table[idx].sym; + int n = table[idx].len; + + if (max_depth > 1 && n < 0) { + bits_priv_skip_remaining(bc, bits); + code = bits_priv_set_idx(bc, code, &n, &nb_bits, table); + if (max_depth > 2 && n < 0) { + bits_priv_skip_remaining(bc, nb_bits); + code = bits_priv_set_idx(bc, code, &n, &nb_bits, table); + } + } + bits_priv_skip_remaining(bc, n); + + return code; +} + +#define BITS_RL_VLC(level, run, bc, table, bits, max_depth) \ + do { \ + int n, nb_bits; \ + unsigned int index = bits_peek(bc, bits); \ + level = table[index].level; \ + n = table[index].len; \ + \ + if (max_depth > 1 && n < 0) { \ + bits_skip(bc, bits); \ + \ + nb_bits = -n; \ + \ + index = bits_peek(bc, nb_bits) + level; \ + level = table[index].level; \ + n = table[index].len; \ + if (max_depth > 2 && n < 0) { \ + bits_skip(bc, nb_bits); \ + nb_bits = -n; \ + \ + index = bits_peek(bc, nb_bits) + level; \ + level = table[index].level; \ + n = table[index].len; \ + } \ + } \ + run = table[index].run; \ + bits_skip(bc, n); \ + } while (0) + +#endif /* AVCODEC_BITSTREAM_H */