15e9aee544
* qatar/release/0.8: (24 commits) apedec: check bits <= 32. truemotion: forbid invalid VLC bitsizes and token values. mov: don't overwrite existing indexes. truemotion2: handle out-of-frame motion vectors through edge extension. lzw: prevent buffer overreads. truemotion2: convert packet header reading to bytestream2. lagarith: fix buffer overreads. raw: forward avpicture_fill() error code in raw_decode(). vc1: Do not read from array if index is invalid. utvideo: port header reading to bytestream2. bytestream: add more unchecked variants for bytestream2 API bytestream: K&R formatting cosmetics bytestream: Add bytestream2 writing API. aac: Reset PS parameters on header decode failure. mov: Do not read past the end of the ctts_data table. xwma: Validate channels and bits_per_coded_sample. asf: reset side data elements on packet copy. vqa: check palette chunk size before reading data. vqavideo: port to bytestream2 API wmavoice: fix stack overread. ... Conflicts: cmdutils.c cmdutils.h libavcodec/lagarith.c libavcodec/truemotion2.c libavcodec/vqavideo.c Merged-by: Michael Niedermayer <michaelni@gmx.at>
60 lines
1.8 KiB
C
60 lines
1.8 KiB
C
/*
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* Lagarith range decoder
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* Copyright (c) 2009 Nathan Caldwell <saintdev (at) gmail.com>
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* Copyright (c) 2009 David Conrad
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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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/**
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* @file
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* Lagarith range decoder
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* @author Nathan Caldwell
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* @author David Conrad
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*/
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#include "get_bits.h"
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#include "lagarithrac.h"
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void lag_rac_init(lag_rac *l, GetBitContext *gb, int length)
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{
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int i, j, left;
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/* According to reference decoder "1st byte is garbage",
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* however, it gets skipped by the call to align_get_bits()
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*/
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align_get_bits(gb);
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left = get_bits_left(gb) >> 3;
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l->bytestream_start =
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l->bytestream = gb->buffer + get_bits_count(gb) / 8;
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l->bytestream_end = l->bytestream_start + FFMIN(length, left);
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l->range = 0x80;
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l->low = *l->bytestream >> 1;
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l->hash_shift = FFMAX(l->scale - 8, 0);
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for (i = j = 0; i < 256; i++) {
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unsigned r = i << l->hash_shift;
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while (l->prob[j + 1] <= r)
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j++;
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l->range_hash[i] = j;
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}
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/* Add conversion factor to hash_shift so we don't have to in lag_get_rac. */
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l->hash_shift += 23;
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}
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