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            int64_t pts = AV_RB32(cur_pu + 13);
216            if (s->last_pts == 0 && s->last_dts == 0)
217                s->dts = pts - 1;
218            else if (s->last_dts != AV_NOPTS_VALUE)
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
276const AVCodecParser 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