mirror of https://github.com/FFmpeg/FFmpeg.git
Allows using both BE and LE bitstream readers in the same file.pull/388/head
Anton Khirnov
4 years ago
parent
8fe551eca0
commit
9177970bca
4 changed files with 611 additions and 450 deletions
@ -0,0 +1,496 @@ |
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/*
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* Copyright (c) 2016 Alexandra Hájková |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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#ifdef BITSTREAM_TEMPLATE_LE |
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# define BS_SUFFIX_LOWER _le |
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# define BS_SUFFIX_UPPER LE |
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#else |
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# define BS_SUFFIX_LOWER _be |
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# define BS_SUFFIX_UPPER BE |
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#endif |
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#define BS_JOIN(x, y, z) x ## y ## z |
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#define BS_JOIN3(x, y, z) BS_JOIN(x, y, z) |
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#define BS_FUNC(x) BS_JOIN3(bits_, x, BS_SUFFIX_LOWER) |
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#define BSCTX BS_JOIN3(Bitstream, Context, BS_SUFFIX_UPPER) |
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typedef struct BSCTX { |
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uint64_t bits; // stores bits read from the buffer
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const uint8_t *buffer, *buffer_end; |
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const uint8_t *ptr; // pointer to the position inside a buffer
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unsigned bits_valid; // number of bits left in bits field
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unsigned size_in_bits; |
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} BSCTX; |
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/**
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* @return |
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* - 0 on successful refill |
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* - a negative number when bitstream end is hit |
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* |
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* Always succeeds when UNCHECKED_BITSTREAM_READER is enabled. |
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*/ |
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static inline int BS_FUNC(priv_refill_64)(BSCTX *bc) |
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{ |
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#if !UNCHECKED_BITSTREAM_READER |
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if (bc->ptr >= bc->buffer_end) |
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return -1; |
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#endif |
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#ifdef BITSTREAM_TEMPLATE_LE |
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bc->bits = AV_RL64(bc->ptr); |
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#else |
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bc->bits = AV_RB64(bc->ptr); |
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#endif |
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bc->ptr += 8; |
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bc->bits_valid = 64; |
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return 0; |
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} |
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/**
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* @return |
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* - 0 on successful refill |
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* - a negative number when bitstream end is hit |
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* |
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* Always succeeds when UNCHECKED_BITSTREAM_READER is enabled. |
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*/ |
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static inline int BS_FUNC(priv_refill_32)(BSCTX *bc) |
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{ |
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#if !UNCHECKED_BITSTREAM_READER |
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if (bc->ptr >= bc->buffer_end) |
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return -1; |
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#endif |
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#ifdef BITSTREAM_TEMPLATE_LE |
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bc->bits |= (uint64_t)AV_RL32(bc->ptr) << bc->bits_valid; |
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#else |
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bc->bits |= (uint64_t)AV_RB32(bc->ptr) << (32 - bc->bits_valid); |
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#endif |
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bc->ptr += 4; |
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bc->bits_valid += 32; |
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return 0; |
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} |
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/**
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* Initialize BitstreamContext. |
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* @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes |
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* larger than the actual read bits because some optimized bitstream |
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* readers read 32 or 64 bits at once and could read over the end |
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* @param bit_size the size of the buffer in bits |
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* @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow. |
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*/ |
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static inline int BS_FUNC(init)(BSCTX *bc, const uint8_t *buffer, |
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unsigned int bit_size) |
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{ |
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unsigned int buffer_size; |
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if (bit_size > INT_MAX - 7 || !buffer) { |
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bc->buffer = NULL; |
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bc->ptr = NULL; |
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bc->bits_valid = 0; |
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return AVERROR_INVALIDDATA; |
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} |
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buffer_size = (bit_size + 7) >> 3; |
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bc->buffer = buffer; |
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bc->buffer_end = buffer + buffer_size; |
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bc->ptr = bc->buffer; |
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bc->size_in_bits = bit_size; |
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bc->bits_valid = 0; |
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bc->bits = 0; |
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BS_FUNC(priv_refill_64)(bc); |
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return 0; |
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} |
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/**
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* Initialize BitstreamContext. |
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* @param buffer bitstream buffer, must be AV_INPUT_BUFFER_PADDING_SIZE bytes |
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* larger than the actual read bits because some optimized bitstream |
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* readers read 32 or 64 bits at once and could read over the end |
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* @param byte_size the size of the buffer in bytes |
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* @return 0 on success, AVERROR_INVALIDDATA if the buffer_size would overflow |
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*/ |
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static inline int BS_FUNC(init8)(BSCTX *bc, const uint8_t *buffer, |
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unsigned int byte_size) |
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{ |
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if (byte_size > INT_MAX / 8) |
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return AVERROR_INVALIDDATA; |
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return BS_FUNC(init)(bc, buffer, byte_size * 8); |
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} |
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/**
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* Return number of bits already read. |
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*/ |
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static inline int BS_FUNC(tell)(const BSCTX *bc) |
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{ |
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return (bc->ptr - bc->buffer) * 8 - bc->bits_valid; |
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} |
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/**
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* Return buffer size in bits. |
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*/ |
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static inline int BS_FUNC(size)(const BSCTX *bc) |
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{ |
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return bc->size_in_bits; |
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} |
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/**
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* Return the number of the bits left in a buffer. |
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*/ |
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static inline int BS_FUNC(left)(const BSCTX *bc) |
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{ |
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return (bc->buffer - bc->ptr) * 8 + bc->size_in_bits + bc->bits_valid; |
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} |
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static inline uint64_t BS_FUNC(priv_val_show)(BSCTX *bc, unsigned int n) |
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{ |
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av_assert2(n > 0 && n <= 64); |
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#ifdef BITSTREAM_TEMPLATE_LE |
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return bc->bits & (UINT64_MAX >> (64 - n)); |
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#else |
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return bc->bits >> (64 - n); |
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#endif |
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} |
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static inline void BS_FUNC(priv_skip_remaining)(BSCTX *bc, unsigned int n) |
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{ |
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#ifdef BITSTREAM_TEMPLATE_LE |
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bc->bits >>= n; |
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#else |
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bc->bits <<= n; |
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#endif |
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bc->bits_valid -= n; |
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} |
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static inline uint64_t BS_FUNC(priv_val_get)(BSCTX *bc, unsigned int n) |
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{ |
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uint64_t ret; |
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av_assert2(n > 0 && n < 64); |
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ret = BS_FUNC(priv_val_show)(bc, n); |
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BS_FUNC(priv_skip_remaining)(bc, n); |
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return ret; |
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} |
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/**
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* Return one bit from the buffer. |
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*/ |
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static inline unsigned int BS_FUNC(read_bit)(BSCTX *bc) |
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{ |
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if (!bc->bits_valid && BS_FUNC(priv_refill_64)(bc) < 0) |
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return 0; |
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return BS_FUNC(priv_val_get)(bc, 1); |
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} |
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/**
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* Return n bits from the buffer, n has to be in the 1-32 range. |
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* May be faster than bits_read() when n is not a compile-time constant and is |
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* known to be non-zero; |
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*/ |
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static inline uint32_t BS_FUNC(read_nz)(BSCTX *bc, unsigned int n) |
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{ |
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av_assert2(n > 0 && n <= 32); |
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if (n > bc->bits_valid) { |
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if (BS_FUNC(priv_refill_32)(bc) < 0) |
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bc->bits_valid = n; |
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} |
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return BS_FUNC(priv_val_get)(bc, n); |
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} |
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/**
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* Return n bits from the buffer, n has to be in the 0-32 range. |
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*/ |
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static inline uint32_t BS_FUNC(read)(BSCTX *bc, unsigned int n) |
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{ |
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av_assert2(n <= 32); |
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if (!n) |
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return 0; |
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return BS_FUNC(read_nz)(bc, n); |
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} |
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/**
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* Return n bits from the buffer, n has to be in the 0-63 range. |
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*/ |
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static inline uint64_t BS_FUNC(read_63)(BSCTX *bc, unsigned int n) |
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{ |
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uint64_t ret = 0; |
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unsigned left = 0; |
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av_assert2(n <= 63); |
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if (!n) |
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return 0; |
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if (n > bc->bits_valid) { |
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left = bc->bits_valid; |
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n -= left; |
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if (left) |
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ret = BS_FUNC(priv_val_get)(bc, left); |
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if (BS_FUNC(priv_refill_64)(bc) < 0) |
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bc->bits_valid = n; |
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} |
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#ifdef BITSTREAM_TEMPLATE_LE |
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ret = BS_FUNC(priv_val_get)(bc, n) << left | ret; |
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#else |
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ret = BS_FUNC(priv_val_get)(bc, n) | ret << n; |
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#endif |
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return ret; |
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} |
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/**
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* Return n bits from the buffer, n has to be in the 0-64 range. |
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*/ |
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static inline uint64_t BS_FUNC(read_64)(BSCTX *bc, unsigned int n) |
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{ |
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av_assert2(n <= 64); |
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if (n == 64) { |
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uint64_t ret = BS_FUNC(read_63)(bc, 63); |
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#ifdef BITSTREAM_TEMPLATE_LE |
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return ret | ((uint64_t)BS_FUNC(read_bit)(bc) << 63); |
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#else |
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return (ret << 1) | (uint64_t)BS_FUNC(read_bit)(bc); |
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#endif |
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} |
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return BS_FUNC(read_63)(bc, n); |
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} |
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/**
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* Return n bits from the buffer as a signed integer. |
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* n has to be in the 0-32 range. |
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*/ |
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static inline int32_t BS_FUNC(read_signed)(BSCTX *bc, unsigned int n) |
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{ |
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return sign_extend(BS_FUNC(read)(bc, n), n); |
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} |
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/**
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* Return n bits from the buffer but do not change the buffer state. |
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* n has to be in the 1-32 range. May |
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*/ |
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static inline uint32_t BS_FUNC(peek_nz)(BSCTX *bc, unsigned int n) |
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{ |
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av_assert2(n > 0 && n <= 32); |
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if (n > bc->bits_valid) |
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BS_FUNC(priv_refill_32)(bc); |
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return BS_FUNC(priv_val_show)(bc, n); |
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} |
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/**
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* Return n bits from the buffer but do not change the buffer state. |
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* n has to be in the 0-32 range. |
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*/ |
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static inline uint32_t BS_FUNC(peek)(BSCTX *bc, unsigned int n) |
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{ |
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av_assert2(n <= 32); |
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if (!n) |
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return 0; |
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return BS_FUNC(peek_nz)(bc, n); |
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} |
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/**
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* Return n bits from the buffer as a signed integer, |
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* do not change the buffer state. |
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* n has to be in the 0-32 range. |
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*/ |
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static inline int BS_FUNC(peek_signed)(BSCTX *bc, unsigned int n) |
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{ |
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return sign_extend(BS_FUNC(peek)(bc, n), n); |
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} |
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/**
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* Skip n bits in the buffer. |
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*/ |
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static inline void BS_FUNC(skip)(BSCTX *bc, unsigned int n) |
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{ |
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if (n < bc->bits_valid) |
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BS_FUNC(priv_skip_remaining)(bc, n); |
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else { |
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n -= bc->bits_valid; |
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bc->bits = 0; |
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bc->bits_valid = 0; |
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if (n >= 64) { |
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unsigned int skip = n / 8; |
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n -= skip * 8; |
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bc->ptr += skip; |
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} |
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BS_FUNC(priv_refill_64)(bc); |
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if (n) |
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BS_FUNC(priv_skip_remaining)(bc, n); |
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} |
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} |
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/**
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* Seek to the given bit position. |
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*/ |
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static inline void BS_FUNC(seek)(BSCTX *bc, unsigned pos) |
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{ |
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bc->ptr = bc->buffer; |
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bc->bits = 0; |
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bc->bits_valid = 0; |
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BS_FUNC(skip)(bc, pos); |
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} |
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/**
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* Skip bits to a byte boundary. |
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*/ |
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static inline const uint8_t *BS_FUNC(align)(BSCTX *bc) |
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{ |
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unsigned int n = -BS_FUNC(tell)(bc) & 7; |
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if (n) |
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BS_FUNC(skip)(bc, n); |
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return bc->buffer + (BS_FUNC(tell)(bc) >> 3); |
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} |
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/**
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* Read MPEG-1 dc-style VLC (sign bit + mantissa with no MSB). |
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* If MSB not set it is negative. |
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* @param n length in bits |
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*/ |
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static inline int BS_FUNC(read_xbits)(BSCTX *bc, unsigned int n) |
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{ |
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int32_t cache = BS_FUNC(peek)(bc, 32); |
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int sign = ~cache >> 31; |
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BS_FUNC(priv_skip_remaining)(bc, n); |
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return ((((uint32_t)(sign ^ cache)) >> (32 - n)) ^ sign) - sign; |
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} |
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/**
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* Return decoded truncated unary code for the values 0, 1, 2. |
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*/ |
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static inline int BS_FUNC(decode012)(BSCTX *bc) |
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{ |
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if (!BS_FUNC(read_bit)(bc)) |
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return 0; |
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else |
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return BS_FUNC(read_bit)(bc) + 1; |
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} |
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/**
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* Return decoded truncated unary code for the values 2, 1, 0. |
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*/ |
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static inline int BS_FUNC(decode210)(BSCTX *bc) |
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{ |
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if (BS_FUNC(read_bit)(bc)) |
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return 0; |
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else |
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return 2 - BS_FUNC(read_bit)(bc); |
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} |
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/* Read sign bit and flip the sign of the provided value accordingly. */ |
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static inline int BS_FUNC(apply_sign)(BSCTX *bc, int val) |
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{ |
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int sign = BS_FUNC(read_signed)(bc, 1); |
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return (val ^ sign) - sign; |
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} |
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static inline int BS_FUNC(skip_1stop_8data)(BSCTX *s) |
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{ |
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if (BS_FUNC(left)(s) <= 0) |
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return AVERROR_INVALIDDATA; |
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while (BS_FUNC(read_bit)(s)) { |
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BS_FUNC(skip)(s, 8); |
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if (BS_FUNC(left)(s) <= 0) |
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return AVERROR_INVALIDDATA; |
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} |
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return 0; |
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} |
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/**
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* Return the LUT element for the given bitstream configuration. |
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*/ |
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static inline int BS_FUNC(priv_set_idx)(BSCTX *bc, int code, int *n, |
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int *nb_bits, const VLCElem *table) |
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{ |
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unsigned idx; |
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*nb_bits = -*n; |
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idx = BS_FUNC(peek)(bc, *nb_bits) + code; |
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*n = table[idx].len; |
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return table[idx].sym; |
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} |
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/**
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* Parse a vlc code. |
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* @param bits is the number of bits which will be read at once, must be |
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* identical to nb_bits in init_vlc() |
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* @param max_depth is the number of times bits bits must be read to completely |
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* read the longest vlc code |
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* = (max_vlc_length + bits - 1) / bits |
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* If the vlc code is invalid and max_depth=1, then no bits will be removed. |
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* If the vlc code is invalid and max_depth>1, then the number of bits removed |
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* is undefined. |
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*/ |
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static inline int BS_FUNC(read_vlc)(BSCTX *bc, const VLCElem *table, |
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int bits, int max_depth) |
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{ |
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int nb_bits; |
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unsigned idx = BS_FUNC(peek)(bc, bits); |
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int code = table[idx].sym; |
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int n = table[idx].len; |
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if (max_depth > 1 && n < 0) { |
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BS_FUNC(priv_skip_remaining)(bc, bits); |
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code = BS_FUNC(priv_set_idx)(bc, code, &n, &nb_bits, table); |
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if (max_depth > 2 && n < 0) { |
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BS_FUNC(priv_skip_remaining)(bc, nb_bits); |
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code = BS_FUNC(priv_set_idx)(bc, code, &n, &nb_bits, table); |
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} |
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} |
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BS_FUNC(priv_skip_remaining)(bc, n); |
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return code; |
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} |
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#undef BSCTX |
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#undef BS_FUNC |
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#undef BS_JOIN3 |
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#undef BS_JOIN |
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#undef BS_SUFFIX_UPPER |
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#undef BS_SUFFIX_LOWER |
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