summaryrefslogtreecommitdiffstats
path: root/libavcodec/vc1_parser.c
blob: 9ca6154e71a3c4a06b8ccba8384727570a91e941 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
/*
 * VC-1 and WMV3 parser
 * Copyright (c) 2006-2007 Konstantin Shishkov
 * Partly based on vc9.c (c) 2005 Anonymous, Alex Beregszaszi, Michael Niedermayer
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg 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.
 *
 * FFmpeg 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 FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

/**
 * @file
 * VC-1 and WMV3 parser
 */

#include "libavutil/attributes.h"
#include "parser.h"
#include "vc1.h"
#include "get_bits.h"
#include "internal.h"

/** The maximum number of bytes of a sequence, entry point or
 *  frame header whose values we pay any attention to */
#define UNESCAPED_THRESHOLD 37

/** The maximum number of bytes of a sequence, entry point or
 *  frame header which must be valid memory (because they are
 *  used to update the bitstream cache in skip_bits() calls)
 */
#define UNESCAPED_LIMIT 144

typedef enum {
    NO_MATCH,
    ONE_ZERO,
    TWO_ZEROS,
    ONE
} VC1ParseSearchState;

typedef struct VC1ParseContext {
    ParseContext pc;
    VC1Context v;
    uint8_t prev_start_code;
    size_t bytes_to_skip;
    uint8_t unesc_buffer[UNESCAPED_LIMIT];
    size_t unesc_index;
    VC1ParseSearchState search_state;
} VC1ParseContext;

static void vc1_extract_header(AVCodecParserContext *s, AVCodecContext *avctx,
                               const uint8_t *buf, int buf_size)
{
    /* Parse the header we just finished unescaping */
    VC1ParseContext *vpc = s->priv_data;
    GetBitContext gb;
    int ret;
    vpc->v.s.avctx = avctx;
    vpc->v.parse_only = 1;
    init_get_bits(&gb, buf, buf_size * 8);
    switch (vpc->prev_start_code) {
    case VC1_CODE_SEQHDR & 0xFF:
        ff_vc1_decode_sequence_header(avctx, &vpc->v, &gb);
        break;
    case VC1_CODE_ENTRYPOINT & 0xFF:
        ff_vc1_decode_entry_point(avctx, &vpc->v, &gb);
        break;
    case VC1_CODE_FRAME & 0xFF:
        if(vpc->v.profile < PROFILE_ADVANCED)
            ret = ff_vc1_parse_frame_header    (&vpc->v, &gb);
        else
            ret = ff_vc1_parse_frame_header_adv(&vpc->v, &gb);

        if (ret < 0)
            break;

        /* keep AV_PICTURE_TYPE_BI internal to VC1 */
        if (vpc->v.s.pict_type == AV_PICTURE_TYPE_BI)
            s->pict_type = AV_PICTURE_TYPE_B;
        else
            s->pict_type = vpc->v.s.pict_type;

        if (avctx->ticks_per_frame > 1){
            // process pulldown flags
            s->repeat_pict = 1;
            // Pulldown flags are only valid when 'broadcast' has been set.
            // So ticks_per_frame will be 2
            if (vpc->v.rff){
                // repeat field
                s->repeat_pict = 2;
            }else if (vpc->v.rptfrm){
                // repeat frames
                s->repeat_pict = vpc->v.rptfrm * 2 + 1;
            }
        }else{
            s->repeat_pict = 0;
        }

        if (vpc->v.broadcast && vpc->v.interlace && !vpc->v.psf)
            s->field_order = vpc->v.tff ? AV_FIELD_TT : AV_FIELD_BB;
        else
            s->field_order = AV_FIELD_PROGRESSIVE;

        break;
    }
    if (avctx->framerate.num)
        avctx->time_base = av_inv_q(av_mul_q(avctx->framerate, (AVRational){avctx->ticks_per_frame, 1}));
}

static int vc1_parse(AVCodecParserContext *s,
                           AVCodecContext *avctx,
                           const uint8_t **poutbuf, int *poutbuf_size,
                           const uint8_t *buf, int buf_size)
{
    /* Here we do the searching for frame boundaries and headers at
     * the same time. Only a minimal amount at the start of each
     * header is unescaped. */
    VC1ParseContext *vpc = s->priv_data;
    int pic_found = vpc->pc.frame_start_found;
    uint8_t *unesc_buffer = vpc->unesc_buffer;
    size_t unesc_index = vpc->unesc_index;
    VC1ParseSearchState search_state = vpc->search_state;
    int start_code_found = 0;
    int next = END_NOT_FOUND;
    int i = vpc->bytes_to_skip;

    if (pic_found && buf_size == 0) {
        /* EOF considered as end of frame */
        memset(unesc_buffer + unesc_index, 0, UNESCAPED_THRESHOLD - unesc_index);
        vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
        next = 0;
    }
    while (i < buf_size) {
        uint8_t b;
        start_code_found = 0;
        while (i < buf_size && unesc_index < UNESCAPED_THRESHOLD) {
            b = buf[i++];
            unesc_buffer[unesc_index++] = b;
            if (search_state <= ONE_ZERO)
                search_state = b ? NO_MATCH : search_state + 1;
            else if (search_state == TWO_ZEROS) {
                if (b == 1)
                    search_state = ONE;
                else if (b > 1) {
                    if (b == 3)
                        unesc_index--; // swallow emulation prevention byte
                    search_state = NO_MATCH;
                }
            }
            else { // search_state == ONE
                // Header unescaping terminates early due to detection of next start code
                search_state = NO_MATCH;
                start_code_found = 1;
                break;
            }
        }
        if ((s->flags & PARSER_FLAG_COMPLETE_FRAMES) &&
                unesc_index >= UNESCAPED_THRESHOLD &&
                vpc->prev_start_code == (VC1_CODE_FRAME & 0xFF))
        {
            // No need to keep scanning the rest of the buffer for
            // start codes if we know it contains a complete frame and
            // we've already unescaped all we need of the frame header
            vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
            break;
        }
        if (unesc_index >= UNESCAPED_THRESHOLD && !start_code_found) {
            while (i < buf_size) {
                if (search_state == NO_MATCH) {
                    i += vpc->v.vc1dsp.startcode_find_candidate(buf + i, buf_size - i);
                    if (i < buf_size) {
                        search_state = ONE_ZERO;
                    }
                    i++;
                } else {
                    b = buf[i++];
                    if (search_state == ONE_ZERO)
                        search_state = b ? NO_MATCH : TWO_ZEROS;
                    else if (search_state == TWO_ZEROS) {
                        if (b >= 1)
                            search_state = b == 1 ? ONE : NO_MATCH;
                    }
                    else { // search_state == ONE
                        search_state = NO_MATCH;
                        start_code_found = 1;
                        break;
                    }
                }
            }
        }
        if (start_code_found) {
            vc1_extract_header(s, avctx, unesc_buffer, unesc_index);

            vpc->prev_start_code = b;
            unesc_index = 0;

            if (!(s->flags & PARSER_FLAG_COMPLETE_FRAMES)) {
                if (!pic_found && (b == (VC1_CODE_FRAME & 0xFF) || b == (VC1_CODE_FIELD & 0xFF))) {
                    pic_found = 1;
                }
                else if (pic_found && b != (VC1_CODE_FIELD & 0xFF) && b != (VC1_CODE_SLICE & 0xFF)) {
                    next = i - 4;
                    pic_found = b == (VC1_CODE_FRAME & 0xFF);
                    break;
                }
            }
        }
    }

    vpc->pc.frame_start_found = pic_found;
    vpc->unesc_index = unesc_index;
    vpc->search_state = search_state;

    if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
        next = buf_size;
    } else {
        if (ff_combine_frame(&vpc->pc, next, &buf, &buf_size) < 0) {
            vpc->bytes_to_skip = 0;
            *poutbuf = NULL;
            *poutbuf_size = 0;
            return buf_size;
        }
    }

    /* If we return with a valid pointer to a combined frame buffer
     * then on the next call then we'll have been unhelpfully rewound
     * by up to 4 bytes (depending upon whether the start code
     * overlapped the input buffer, and if so by how much). We don't
     * want this: it will either cause spurious second detections of
     * the start code we've already seen, or cause extra bytes to be
     * inserted at the start of the unescaped buffer. */
    vpc->bytes_to_skip = 4;
    if (next < 0 && next != END_NOT_FOUND)
        vpc->bytes_to_skip += next;

    *poutbuf = buf;
    *poutbuf_size = buf_size;
    return next;
}

static int vc1_split(AVCodecContext *avctx,
                           const uint8_t *buf, int buf_size)
{
    uint32_t state = -1;
    int charged = 0;
    const uint8_t *ptr = buf, *end = buf + buf_size;

    while (ptr < end) {
        ptr = avpriv_find_start_code(ptr, end, &state);
        if (state == VC1_CODE_SEQHDR || state == VC1_CODE_ENTRYPOINT) {
            charged = 1;
        } else if (charged && IS_MARKER(state))
            return ptr - 4 - buf;
    }

    return 0;
}

static av_cold int vc1_parse_init(AVCodecParserContext *s)
{
    VC1ParseContext *vpc = s->priv_data;
    vpc->v.s.slice_context_count = 1;
    vpc->v.first_pic_header_flag = 1;
    vpc->prev_start_code = 0;
    vpc->bytes_to_skip = 0;
    vpc->unesc_index = 0;
    vpc->search_state = NO_MATCH;
    return ff_vc1_init_common(&vpc->v);
}

AVCodecParser ff_vc1_parser = {
    .codec_ids      = { AV_CODEC_ID_VC1 },
    .priv_data_size = sizeof(VC1ParseContext),
    .parser_init    = vc1_parse_init,
    .parser_parse   = vc1_parse,
    .parser_close   = ff_parse_close,
    .split          = vc1_split,
};
OpenPOWER on IntegriCloud