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path: root/libavcodec/dirac_parser.c (plain)
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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 */
43typedef 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
56static 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
94typedef struct DiracParseUnit {
95 int next_pu_offset;
96 int prev_pu_offset;
97 uint8_t pu_type;
98} DiracParseUnit;
99
100static int unpack_parse_unit(DiracParseUnit *pu, DiracParseContext *pc,
101 int offset)
102{
103 int i;
104 int8_t *start;
105 static const uint8_t valid_pu_types[] = {
106 0x00, 0x10, 0x20, 0x30, 0x08, 0x48, 0xC8, 0xE8, 0x0A, 0x0C, 0x0D, 0x0E,
107 0x4C, 0x09, 0xCC, 0x88, 0xCB
108 };
109
110 if (offset < 0 || pc->index - 13 < offset)
111 return 0;
112
113 start = pc->buffer + offset;
114 pu->pu_type = start[4];
115
116 pu->next_pu_offset = AV_RB32(start + 5);
117 pu->prev_pu_offset = AV_RB32(start + 9);
118
119 /* Check for valid parse code */
120 for (i = 0; i < 17; i++)
121 if (valid_pu_types[i] == pu->pu_type)
122 break;
123 if (i == 17)
124 return 0;
125
126 if (pu->pu_type == 0x10 && pu->next_pu_offset == 0x00)
127 pu->next_pu_offset = 13; /* The length of a parse info header */
128
129 /* Check if the parse offsets are somewhat sane */
130 if ((pu->next_pu_offset && pu->next_pu_offset < 13) ||
131 (pu->prev_pu_offset && pu->prev_pu_offset < 13))
132 return 0;
133
134 return 1;
135}
136
137static int dirac_combine_frame(AVCodecParserContext *s, AVCodecContext *avctx,
138 int next, const uint8_t **buf, int *buf_size)
139{
140 int parse_timing_info = (s->pts == AV_NOPTS_VALUE &&
141 s->dts == AV_NOPTS_VALUE);
142 DiracParseContext *pc = s->priv_data;
143
144 if (pc->overread_index) {
145 memmove(pc->buffer, pc->buffer + pc->overread_index,
146 pc->index - pc->overread_index);
147 pc->index -= pc->overread_index;
148 pc->overread_index = 0;
149 if (*buf_size == 0 && pc->buffer[4] == 0x10) {
150 *buf = pc->buffer;
151 *buf_size = pc->index;
152 return 0;
153 }
154 }
155
156 if (next == -1) {
157 /* Found a possible frame start but not a frame end */
158 void *new_buffer =
159 av_fast_realloc(pc->buffer, &pc->buffer_size,
160 pc->index + (*buf_size - pc->sync_offset));
161 if (!new_buffer)
162 return AVERROR(ENOMEM);
163 pc->buffer = new_buffer;
164 memcpy(pc->buffer + pc->index, (*buf + pc->sync_offset),
165 *buf_size - pc->sync_offset);
166 pc->index += *buf_size - pc->sync_offset;
167 return -1;
168 } else {
169 /* Found a possible frame start and a possible frame end */
170 DiracParseUnit pu1, pu;
171 void *new_buffer = av_fast_realloc(pc->buffer, &pc->buffer_size,
172 pc->index + next);
173 if (!new_buffer)
174 return AVERROR(ENOMEM);
175 pc->buffer = new_buffer;
176 memcpy(pc->buffer + pc->index, *buf, next);
177 pc->index += next;
178
179 /* Need to check if we have a valid Parse Unit. We can't go by the
180 * sync pattern 'BBCD' alone because arithmetic coding of the residual
181 * and motion data can cause the pattern triggering a false start of
182 * frame. So check if the previous parse offset of the next parse unit
183 * is equal to the next parse offset of the current parse unit then
184 * we can be pretty sure that we have a valid parse unit */
185 if (!unpack_parse_unit(&pu1, pc, pc->index - 13) ||
186 !unpack_parse_unit(&pu, pc, pc->index - 13 - pu1.prev_pu_offset) ||
187 pu.next_pu_offset != pu1.prev_pu_offset ||
188 pc->index < pc->dirac_unit_size + 13LL + pu1.prev_pu_offset
189 ) {
190 pc->index -= 9;
191 *buf_size = next - 9;
192 pc->header_bytes_needed = 9;
193 return -1;
194 }
195
196 /* All non-frame data must be accompanied by frame data. This is to
197 * ensure that pts is set correctly. So if the current parse unit is
198 * not frame data, wait for frame data to come along */
199
200 pc->dirac_unit = pc->buffer + pc->index - 13 -
201 pu1.prev_pu_offset - pc->dirac_unit_size;
202
203 pc->dirac_unit_size += pu.next_pu_offset;
204
205 if ((pu.pu_type & 0x08) != 0x08) {
206 pc->header_bytes_needed = 9;
207 *buf_size = next;
208 return -1;
209 }
210
211 /* Get the picture number to set the pts and dts*/
212 if (parse_timing_info && pu1.prev_pu_offset >= 13) {
213 uint8_t *cur_pu = pc->buffer +
214 pc->index - 13 - pu1.prev_pu_offset;
215 int pts = AV_RB32(cur_pu + 13);
216 if (s->last_pts == 0 && s->last_dts == 0)
217 s->dts = pts - 1;
218 else
219 s->dts = s->last_dts + 1;
220 s->pts = pts;
221 if (!avctx->has_b_frames && (cur_pu[4] & 0x03))
222 avctx->has_b_frames = 1;
223 }
224 if (avctx->has_b_frames && s->pts == s->dts)
225 s->pict_type = AV_PICTURE_TYPE_B;
226
227 /* Finally have a complete Dirac data unit */
228 *buf = pc->dirac_unit;
229 *buf_size = pc->dirac_unit_size;
230
231 pc->dirac_unit_size = 0;
232 pc->overread_index = pc->index - 13;
233 pc->header_bytes_needed = 9;
234 }
235 return next;
236}
237
238static int dirac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
239 const uint8_t **poutbuf, int *poutbuf_size,
240 const uint8_t *buf, int buf_size)
241{
242 DiracParseContext *pc = s->priv_data;
243 int next;
244
245 *poutbuf = NULL;
246 *poutbuf_size = 0;
247
248 if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
249 next = buf_size;
250 *poutbuf = buf;
251 *poutbuf_size = buf_size;
252 /* Assume that data has been packetized into an encapsulation unit. */
253 } else {
254 next = find_frame_end(pc, buf, buf_size);
255 if (!pc->is_synced && next == -1)
256 /* No frame start found yet. So throw away the entire buffer. */
257 return buf_size;
258
259 if (dirac_combine_frame(s, avctx, next, &buf, &buf_size) < 0)
260 return buf_size;
261 }
262
263 *poutbuf = buf;
264 *poutbuf_size = buf_size;
265 return next;
266}
267
268static void dirac_parse_close(AVCodecParserContext *s)
269{
270 DiracParseContext *pc = s->priv_data;
271
272 if (pc->buffer_size > 0)
273 av_freep(&pc->buffer);
274}
275
276AVCodecParser ff_dirac_parser = {
277 .codec_ids = { AV_CODEC_ID_DIRAC },
278 .priv_data_size = sizeof(DiracParseContext),
279 .parser_parse = dirac_parse,
280 .parser_close = dirac_parse_close,
281};
282
generated by cgit at 2024-05-17 05:12:54 (GMT)