| 1 | /* |
| 2 | * Dirac parser |
| 3 | * |
| 4 | * Copyright (c) 2007-2008 Marco Gerards <marco@gnu.org> |
| 5 | * Copyright (c) 2008 BBC, Anuradha Suraparaju <asuraparaju@gmail.com> |
| 6 | * |
| 7 | * This file is part of FFmpeg. |
| 8 | * |
| 9 | * FFmpeg is free software; you can redistribute it and/or |
| 10 | * modify it under the terms of the GNU Lesser General Public |
| 11 | * License as published by the Free Software Foundation; either |
| 12 | * version 2.1 of the License, or (at your option) any later version. |
| 13 | * |
| 14 | * FFmpeg is distributed in the hope that it will be useful, |
| 15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 17 | * Lesser General Public License for more details. |
| 18 | * |
| 19 | * You should have received a copy of the GNU Lesser General Public |
| 20 | * License along with FFmpeg; if not, write to the Free Software |
| 21 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 22 | */ |
| 23 | |
| 24 | /** |
| 25 | * @file |
| 26 | * Dirac Parser |
| 27 | * @author Marco Gerards <marco@gnu.org> |
| 28 | */ |
| 29 | |
| 30 | #include <string.h> |
| 31 | |
| 32 | #include "libavutil/intreadwrite.h" |
| 33 | #include "libavutil/mem.h" |
| 34 | |
| 35 | #include "parser.h" |
| 36 | |
| 37 | #define DIRAC_PARSE_INFO_PREFIX 0x42424344 |
| 38 | |
| 39 | /** |
| 40 | * Find the end of the current frame in the bitstream. |
| 41 | * @return the position of the first byte of the next frame or -1 |
| 42 | */ |
| 43 | typedef struct DiracParseContext { |
| 44 | int state; |
| 45 | int is_synced; |
| 46 | int sync_offset; |
| 47 | int header_bytes_needed; |
| 48 | int overread_index; |
| 49 | int buffer_size; |
| 50 | int index; |
| 51 | uint8_t *buffer; |
| 52 | int dirac_unit_size; |
| 53 | uint8_t *dirac_unit; |
| 54 | } DiracParseContext; |
| 55 | |
| 56 | static int find_frame_end(DiracParseContext *pc, |
| 57 | const uint8_t *buf, int buf_size) |
| 58 | { |
| 59 | uint32_t state = pc->state; |
| 60 | int i = 0; |
| 61 | |
| 62 | if (!pc->is_synced) { |
| 63 | for (i = 0; i < buf_size; i++) { |
| 64 | state = (state << 8) | buf[i]; |
| 65 | if (state == DIRAC_PARSE_INFO_PREFIX) { |
| 66 | state = -1; |
| 67 | pc->is_synced = 1; |
| 68 | pc->header_bytes_needed = 9; |
| 69 | pc->sync_offset = i; |
| 70 | break; |
| 71 | } |
| 72 | } |
| 73 | } |
| 74 | |
| 75 | if (pc->is_synced) { |
| 76 | pc->sync_offset = 0; |
| 77 | for (; i < buf_size; i++) { |
| 78 | if (state == DIRAC_PARSE_INFO_PREFIX) { |
| 79 | if ((buf_size - i) >= pc->header_bytes_needed) { |
| 80 | pc->state = -1; |
| 81 | return i + pc->header_bytes_needed; |
| 82 | } else { |
| 83 | pc->header_bytes_needed = 9 - (buf_size - i); |
| 84 | break; |
| 85 | } |
| 86 | } else |
| 87 | state = (state << 8) | buf[i]; |
| 88 | } |
| 89 | } |
| 90 | pc->state = state; |
| 91 | return -1; |
| 92 | } |
| 93 | |
| 94 | typedef struct DiracParseUnit { |
| 95 | int next_pu_offset; |
| 96 | int prev_pu_offset; |
| 97 | uint8_t pu_type; |
| 98 | } DiracParseUnit; |
| 99 | |
| 100 | static int unpack_parse_unit(DiracParseUnit *pu, DiracParseContext *pc, |
| 101 | int offset) |
| 102 | { |
| 103 | uint8_t *start = pc->buffer + offset; |
| 104 | uint8_t *end = pc->buffer + pc->index; |
| 105 | if (start < pc->buffer || (start + 13 > end)) |
| 106 | return 0; |
| 107 | pu->pu_type = start[4]; |
| 108 | |
| 109 | pu->next_pu_offset = AV_RB32(start + 5); |
| 110 | pu->prev_pu_offset = AV_RB32(start + 9); |
| 111 | |
| 112 | if (pu->pu_type == 0x10 && pu->next_pu_offset == 0) |
| 113 | pu->next_pu_offset = 13; |
| 114 | |
| 115 | return 1; |
| 116 | } |
| 117 | |
| 118 | static int dirac_combine_frame(AVCodecParserContext *s, AVCodecContext *avctx, |
| 119 | int next, const uint8_t **buf, int *buf_size) |
| 120 | { |
| 121 | int parse_timing_info = (s->pts == AV_NOPTS_VALUE && |
| 122 | s->dts == AV_NOPTS_VALUE); |
| 123 | DiracParseContext *pc = s->priv_data; |
| 124 | |
| 125 | if (pc->overread_index) { |
| 126 | memcpy(pc->buffer, pc->buffer + pc->overread_index, |
| 127 | pc->index - pc->overread_index); |
| 128 | pc->index -= pc->overread_index; |
| 129 | pc->overread_index = 0; |
| 130 | if (*buf_size == 0 && pc->buffer[4] == 0x10) { |
| 131 | *buf = pc->buffer; |
| 132 | *buf_size = pc->index; |
| 133 | return 0; |
| 134 | } |
| 135 | } |
| 136 | |
| 137 | if (next == -1) { |
| 138 | /* Found a possible frame start but not a frame end */ |
| 139 | void *new_buffer = |
| 140 | av_fast_realloc(pc->buffer, &pc->buffer_size, |
| 141 | pc->index + (*buf_size - pc->sync_offset)); |
| 142 | pc->buffer = new_buffer; |
| 143 | memcpy(pc->buffer + pc->index, (*buf + pc->sync_offset), |
| 144 | *buf_size - pc->sync_offset); |
| 145 | pc->index += *buf_size - pc->sync_offset; |
| 146 | return -1; |
| 147 | } else { |
| 148 | /* Found a possible frame start and a possible frame end */ |
| 149 | DiracParseUnit pu1, pu; |
| 150 | void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size, |
| 151 | pc->index + next); |
| 152 | pc->buffer = new_buffer; |
| 153 | memcpy(pc->buffer + pc->index, *buf, next); |
| 154 | pc->index += next; |
| 155 | |
| 156 | /* Need to check if we have a valid Parse Unit. We can't go by the |
| 157 | * sync pattern 'BBCD' alone because arithmetic coding of the residual |
| 158 | * and motion data can cause the pattern triggering a false start of |
| 159 | * frame. So check if the previous parse offset of the next parse unit |
| 160 | * is equal to the next parse offset of the current parse unit then |
| 161 | * we can be pretty sure that we have a valid parse unit */ |
| 162 | if (!unpack_parse_unit(&pu1, pc, pc->index - 13) || |
| 163 | !unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) || |
| 164 | pu.next_pu_offset != pu1.prev_pu_offset || |
| 165 | pc->index < pc->dirac_unit_size + 13LL + pu1.prev_pu_offset |
| 166 | ) { |
| 167 | pc->index -= 9; |
| 168 | *buf_size = next - 9; |
| 169 | pc->header_bytes_needed = 9; |
| 170 | return -1; |
| 171 | } |
| 172 | |
| 173 | /* All non-frame data must be accompanied by frame data. This is to |
| 174 | * ensure that pts is set correctly. So if the current parse unit is |
| 175 | * not frame data, wait for frame data to come along */ |
| 176 | |
| 177 | pc->dirac_unit = pc->buffer + pc->index - 13 - |
| 178 | pu1.prev_pu_offset - pc->dirac_unit_size; |
| 179 | |
| 180 | pc->dirac_unit_size += pu.next_pu_offset; |
| 181 | |
| 182 | if ((pu.pu_type & 0x08) != 0x08) { |
| 183 | pc->header_bytes_needed = 9; |
| 184 | *buf_size = next; |
| 185 | return -1; |
| 186 | } |
| 187 | |
| 188 | /* Get the picture number to set the pts and dts*/ |
| 189 | if (parse_timing_info) { |
| 190 | uint8_t *cur_pu = pc->buffer + |
| 191 | pc->index - 13 - pu1.prev_pu_offset; |
| 192 | int pts = AV_RB32(cur_pu + 13); |
| 193 | if (s->last_pts == 0 && s->last_dts == 0) |
| 194 | s->dts = pts - 1; |
| 195 | else |
| 196 | s->dts = s->last_dts + 1; |
| 197 | s->pts = pts; |
| 198 | if (!avctx->has_b_frames && (cur_pu[4] & 0x03)) |
| 199 | avctx->has_b_frames = 1; |
| 200 | } |
| 201 | if (avctx->has_b_frames && s->pts == s->dts) |
| 202 | s->pict_type = AV_PICTURE_TYPE_B; |
| 203 | |
| 204 | /* Finally have a complete Dirac data unit */ |
| 205 | *buf = pc->dirac_unit; |
| 206 | *buf_size = pc->dirac_unit_size; |
| 207 | |
| 208 | pc->dirac_unit_size = 0; |
| 209 | pc->overread_index = pc->index - 13; |
| 210 | pc->header_bytes_needed = 9; |
| 211 | } |
| 212 | return next; |
| 213 | } |
| 214 | |
| 215 | static int dirac_parse(AVCodecParserContext *s, AVCodecContext *avctx, |
| 216 | const uint8_t **poutbuf, int *poutbuf_size, |
| 217 | const uint8_t *buf, int buf_size) |
| 218 | { |
| 219 | DiracParseContext *pc = s->priv_data; |
| 220 | int next; |
| 221 | |
| 222 | *poutbuf = NULL; |
| 223 | *poutbuf_size = 0; |
| 224 | |
| 225 | if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) { |
| 226 | next = buf_size; |
| 227 | *poutbuf = buf; |
| 228 | *poutbuf_size = buf_size; |
| 229 | /* Assume that data has been packetized into an encapsulation unit. */ |
| 230 | } else { |
| 231 | next = find_frame_end(pc, buf, buf_size); |
| 232 | if (!pc->is_synced && next == -1) |
| 233 | /* No frame start found yet. So throw away the entire buffer. */ |
| 234 | return buf_size; |
| 235 | |
| 236 | if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0) |
| 237 | return buf_size; |
| 238 | } |
| 239 | |
| 240 | *poutbuf = buf; |
| 241 | *poutbuf_size = buf_size; |
| 242 | return next; |
| 243 | } |
| 244 | |
| 245 | static void dirac_parse_close(AVCodecParserContext *s) |
| 246 | { |
| 247 | DiracParseContext *pc = s->priv_data; |
| 248 | |
| 249 | if (pc->buffer_size > 0) |
| 250 | av_free(pc->buffer); |
| 251 | } |
| 252 | |
| 253 | AVCodecParser ff_dirac_parser = { |
| 254 | .codec_ids = { AV_CODEC_ID_DIRAC }, |
| 255 | .priv_data_size = sizeof(DiracParseContext), |
| 256 | .parser_parse = dirac_parse, |
| 257 | .parser_close = dirac_parse_close, |
| 258 | }; |