mirror of
https://git.ffmpeg.org/ffmpeg.git
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263 lines
8.4 KiB
C
263 lines
8.4 KiB
C
/*
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* Dirac parser
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*
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* Copyright (c) 2007-2008 Marco Gerards <marco@gnu.org>
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* Copyright (c) 2008 BBC, Anuradha Suraparaju <asuraparaju@gmail.com>
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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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* Dirac Parser
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* @author Marco Gerards <marco@gnu.org>
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*/
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#include <string.h>
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#include "libavutil/intreadwrite.h"
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#include "libavutil/mem.h"
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#include "parser.h"
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#define DIRAC_PARSE_INFO_PREFIX 0x42424344
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/**
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* Find the end of the current frame in the bitstream.
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* @return the position of the first byte of the next frame or -1
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*/
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typedef struct DiracParseContext {
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int state;
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int is_synced;
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int sync_offset;
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int header_bytes_needed;
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int overread_index;
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int buffer_size;
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int index;
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uint8_t *buffer;
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int dirac_unit_size;
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uint8_t *dirac_unit;
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} DiracParseContext;
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static int find_frame_end(DiracParseContext *pc,
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const uint8_t *buf, int buf_size)
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{
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uint32_t state = pc->state;
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int i = 0;
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if (!pc->is_synced) {
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for (i = 0; i < buf_size; i++) {
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state = (state << 8) | buf[i];
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if (state == DIRAC_PARSE_INFO_PREFIX) {
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state = -1;
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pc->is_synced = 1;
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pc->header_bytes_needed = 9;
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pc->sync_offset = i;
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break;
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}
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}
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}
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if (pc->is_synced) {
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pc->sync_offset = 0;
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for (; i < buf_size; i++) {
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if (state == DIRAC_PARSE_INFO_PREFIX) {
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if ((buf_size - i) >= pc->header_bytes_needed) {
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pc->state = -1;
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return i + pc->header_bytes_needed;
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} else {
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pc->header_bytes_needed = 9 - (buf_size - i);
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break;
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}
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} else
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state = (state << 8) | buf[i];
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}
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}
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pc->state = state;
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return -1;
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}
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typedef struct DiracParseUnit {
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int next_pu_offset;
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int prev_pu_offset;
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uint8_t pu_type;
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} DiracParseUnit;
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static int unpack_parse_unit(DiracParseUnit *pu, DiracParseContext *pc,
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int offset)
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{
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uint8_t *start = pc->buffer + offset;
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uint8_t *end = pc->buffer + pc->index;
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if (start < pc->buffer || (start + 13 > end))
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return 0;
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pu->pu_type = start[4];
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pu->next_pu_offset = AV_RB32(start + 5);
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pu->prev_pu_offset = AV_RB32(start + 9);
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if (pu->pu_type == 0x10 && pu->next_pu_offset == 0)
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pu->next_pu_offset = 13;
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return 1;
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}
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static int dirac_combine_frame(AVCodecParserContext *s, AVCodecContext *avctx,
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int next, const uint8_t **buf, int *buf_size)
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{
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int parse_timing_info = (s->pts == AV_NOPTS_VALUE &&
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s->dts == AV_NOPTS_VALUE);
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DiracParseContext *pc = s->priv_data;
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if (pc->overread_index) {
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memcpy(pc->buffer, pc->buffer + pc->overread_index,
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pc->index - pc->overread_index);
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pc->index -= pc->overread_index;
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pc->overread_index = 0;
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if (*buf_size == 0 && pc->buffer[4] == 0x10) {
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*buf = pc->buffer;
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*buf_size = pc->index;
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return 0;
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}
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}
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if (next == -1) {
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/* Found a possible frame start but not a frame end */
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void *new_buffer =
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av_fast_realloc(pc->buffer, &pc->buffer_size,
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pc->index + (*buf_size - pc->sync_offset));
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if (!new_buffer)
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return AVERROR(ENOMEM);
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pc->buffer = new_buffer;
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memcpy(pc->buffer + pc->index, (*buf + pc->sync_offset),
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*buf_size - pc->sync_offset);
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pc->index += *buf_size - pc->sync_offset;
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return -1;
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} else {
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/* Found a possible frame start and a possible frame end */
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DiracParseUnit pu1, pu;
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void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
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pc->index + next);
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if (!new_buffer)
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return AVERROR(ENOMEM);
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pc->buffer = new_buffer;
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memcpy(pc->buffer + pc->index, *buf, next);
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pc->index += next;
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/* Need to check if we have a valid Parse Unit. We can't go by the
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* sync pattern 'BBCD' alone because arithmetic coding of the residual
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* and motion data can cause the pattern triggering a false start of
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* frame. So check if the previous parse offset of the next parse unit
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* is equal to the next parse offset of the current parse unit then
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* we can be pretty sure that we have a valid parse unit */
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if (!unpack_parse_unit(&pu1, pc, pc->index - 13) ||
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!unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) ||
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pu.next_pu_offset != pu1.prev_pu_offset ||
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pc->index < pc->dirac_unit_size + 13LL + pu1.prev_pu_offset
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) {
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pc->index -= 9;
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*buf_size = next - 9;
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pc->header_bytes_needed = 9;
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return -1;
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}
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/* All non-frame data must be accompanied by frame data. This is to
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* ensure that pts is set correctly. So if the current parse unit is
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* not frame data, wait for frame data to come along */
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pc->dirac_unit = pc->buffer + pc->index - 13 -
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pu1.prev_pu_offset - pc->dirac_unit_size;
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pc->dirac_unit_size += pu.next_pu_offset;
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if ((pu.pu_type & 0x08) != 0x08) {
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pc->header_bytes_needed = 9;
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*buf_size = next;
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return -1;
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}
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/* Get the picture number to set the pts and dts*/
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if (parse_timing_info) {
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uint8_t *cur_pu = pc->buffer +
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pc->index - 13 - pu1.prev_pu_offset;
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int pts = AV_RB32(cur_pu + 13);
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if (s->last_pts == 0 && s->last_dts == 0)
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s->dts = pts - 1;
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else
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s->dts = s->last_dts + 1;
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s->pts = pts;
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if (!avctx->has_b_frames && (cur_pu[4] & 0x03))
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avctx->has_b_frames = 1;
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}
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if (avctx->has_b_frames && s->pts == s->dts)
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s->pict_type = AV_PICTURE_TYPE_B;
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/* Finally have a complete Dirac data unit */
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*buf = pc->dirac_unit;
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*buf_size = pc->dirac_unit_size;
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pc->dirac_unit_size = 0;
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pc->overread_index = pc->index - 13;
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pc->header_bytes_needed = 9;
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}
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return next;
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}
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static int dirac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
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const uint8_t **poutbuf, int *poutbuf_size,
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const uint8_t *buf, int buf_size)
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{
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DiracParseContext *pc = s->priv_data;
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int next;
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*poutbuf = NULL;
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*poutbuf_size = 0;
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if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
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next = buf_size;
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*poutbuf = buf;
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*poutbuf_size = buf_size;
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/* Assume that data has been packetized into an encapsulation unit. */
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} else {
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next = find_frame_end(pc, buf, buf_size);
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if (!pc->is_synced && next == -1)
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/* No frame start found yet. So throw away the entire buffer. */
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return buf_size;
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if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0)
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return buf_size;
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}
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*poutbuf = buf;
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*poutbuf_size = buf_size;
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return next;
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}
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static void dirac_parse_close(AVCodecParserContext *s)
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{
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DiracParseContext *pc = s->priv_data;
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if (pc->buffer_size > 0)
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av_freep(&pc->buffer);
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}
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AVCodecParser ff_dirac_parser = {
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.codec_ids = { AV_CODEC_ID_DIRAC },
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.priv_data_size = sizeof(DiracParseContext),
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.parser_parse = dirac_parse,
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.parser_close = dirac_parse_close,
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};
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