/* * Dirac parser * * Copyright (c) 2007-2008 Marco Gerards <marco@gnu.org> * Copyright (c) 2008 BBC, Anuradha Suraparaju <asuraparaju@gmail.com> * * This file is part of Libav. * * Libav 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. * * Libav 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 Libav; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ /** * @file * Dirac Parser * @author Marco Gerards <marco@gnu.org> */ #include "libavutil/intreadwrite.h" #include "parser.h" #define DIRAC_PARSE_INFO_PREFIX 0x42424344 /** * Find the end of the current frame in the bitstream. * @return the position of the first byte of the next frame or -1 */ typedef struct DiracParseContext { int state; int is_synced; int sync_offset; int header_bytes_needed; int overread_index; int buffer_size; int index; uint8_t *buffer; int dirac_unit_size; uint8_t *dirac_unit; } DiracParseContext; static int find_frame_end(DiracParseContext *pc, const uint8_t *buf, int buf_size) { uint32_t state = pc->state; int i = 0; if (!pc->is_synced) { for (i = 0; i < buf_size; i++) { state = (state << 8) | buf[i]; if (state == DIRAC_PARSE_INFO_PREFIX) { state = -1; pc->is_synced = 1; pc->header_bytes_needed = 9; pc->sync_offset = i; break; } } } if (pc->is_synced) { pc->sync_offset = 0; for (; i < buf_size; i++) { if (state == DIRAC_PARSE_INFO_PREFIX) { if ((buf_size-i) >= pc->header_bytes_needed) { pc->state = -1; return i + pc->header_bytes_needed; } else { pc->header_bytes_needed = 9-(buf_size-i); break; } } else state = (state << 8) | buf[i]; } } pc->state = state; return -1; } typedef struct DiracParseUnit { int next_pu_offset; int prev_pu_offset; uint8_t pu_type; } DiracParseUnit; static int unpack_parse_unit(DiracParseUnit *pu, DiracParseContext *pc, int offset) { uint8_t *start = pc->buffer + offset; uint8_t *end = pc->buffer + pc->index; if (start < pc->buffer || (start+13 > end)) return 0; pu->pu_type = start[4]; pu->next_pu_offset = AV_RB32(start+5); pu->prev_pu_offset = AV_RB32(start+9); if (pu->pu_type == 0x10 && pu->next_pu_offset == 0) pu->next_pu_offset = 13; return 1; } static int dirac_combine_frame(AVCodecParserContext *s, AVCodecContext *avctx, int next, const uint8_t **buf, int *buf_size) { int parse_timing_info = (s->pts == AV_NOPTS_VALUE && s->dts == AV_NOPTS_VALUE); DiracParseContext *pc = s->priv_data; if (pc->overread_index) { memcpy(pc->buffer, pc->buffer + pc->overread_index, pc->index - pc->overread_index); pc->index -= pc->overread_index; pc->overread_index = 0; if (*buf_size == 0 && pc->buffer[4] == 0x10) { *buf = pc->buffer; *buf_size = pc->index; return 0; } } if ( next == -1) { /* Found a possible frame start but not a frame end */ void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size, pc->index + (*buf_size - pc->sync_offset)); pc->buffer = new_buffer; memcpy(pc->buffer+pc->index, (*buf + pc->sync_offset), *buf_size - pc->sync_offset); pc->index += *buf_size - pc->sync_offset; return -1; } else { /* Found a possible frame start and a possible frame end */ DiracParseUnit pu1, pu; void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size, pc->index + next); pc->buffer = new_buffer; memcpy(pc->buffer + pc->index, *buf, next); pc->index += next; /* Need to check if we have a valid Parse Unit. We can't go by the * sync pattern 'BBCD' alone because arithmetic coding of the residual * and motion data can cause the pattern triggering a false start of * frame. So check if the previous parse offset of the next parse unit * is equal to the next parse offset of the current parse unit then * we can be pretty sure that we have a valid parse unit */ if (!unpack_parse_unit(&pu1, pc, pc->index - 13) || !unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) || pu.next_pu_offset != pu1.prev_pu_offset) { pc->index -= 9; *buf_size = next-9; pc->header_bytes_needed = 9; return -1; } /* All non-frame data must be accompanied by frame data. This is to * ensure that pts is set correctly. So if the current parse unit is * not frame data, wait for frame data to come along */ pc->dirac_unit = pc->buffer + pc->index - 13 - pu1.prev_pu_offset - pc->dirac_unit_size; pc->dirac_unit_size += pu.next_pu_offset; if ((pu.pu_type&0x08) != 0x08) { pc->header_bytes_needed = 9; *buf_size = next; return -1; } /* Get the picture number to set the pts and dts*/ if (parse_timing_info) { uint8_t *cur_pu = pc->buffer + pc->index - 13 - pu1.prev_pu_offset; int pts = AV_RB32(cur_pu + 13); if (s->last_pts == 0 && s->last_dts == 0) s->dts = pts - 1; else s->dts = s->last_dts+1; s->pts = pts; if (!avctx->has_b_frames && (cur_pu[4] & 0x03)) avctx->has_b_frames = 1; } if (avctx->has_b_frames && s->pts == s->dts) s->pict_type = AV_PICTURE_TYPE_B; /* Finally have a complete Dirac data unit */ *buf = pc->dirac_unit; *buf_size = pc->dirac_unit_size; pc->dirac_unit_size = 0; pc->overread_index = pc->index-13; pc->header_bytes_needed = 9; } return next; } static int dirac_parse(AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size) { DiracParseContext *pc = s->priv_data; int next; *poutbuf = NULL; *poutbuf_size = 0; if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) { next = buf_size; *poutbuf = buf; *poutbuf_size = buf_size; /* Assume that data has been packetized into an encapsulation unit. */ } else { next = find_frame_end(pc, buf, buf_size); if (!pc->is_synced && next == -1) { /* No frame start found yet. So throw away the entire buffer. */ return buf_size; } if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0) { return buf_size; } } *poutbuf = buf; *poutbuf_size = buf_size; return next; } static void dirac_parse_close(AVCodecParserContext *s) { DiracParseContext *pc = s->priv_data; if (pc->buffer_size > 0) av_free(pc->buffer); } AVCodecParser ff_dirac_parser = { { CODEC_ID_DIRAC }, sizeof(DiracParseContext), NULL, dirac_parse, dirac_parse_close, };