1/*
2 * VC-1 and WMV3 parser
3 * Copyright (c) 2006-2007 Konstantin Shishkov
4 * Partly based on vc9.c (c) 2005 Anonymous, Alex Beregszaszi, Michael Niedermayer
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23/**
24 * @file
25 * VC-1 and WMV3 parser
26 */
27
28#include "libavutil/attributes.h"
29#include "parser.h"
30#include "vc1.h"
31#include "get_bits.h"
32
33/** The maximum number of bytes of a sequence, entry point or
34 *  frame header whose values we pay any attention to */
35#define UNESCAPED_THRESHOLD 37
36
37/** The maximum number of bytes of a sequence, entry point or
38 *  frame header which must be valid memory (because they are
39 *  used to update the bitstream cache in skip_bits() calls)
40 */
41#define UNESCAPED_LIMIT 144
42
43typedef enum {
44    NO_MATCH,
45    ONE_ZERO,
46    TWO_ZEROS,
47    ONE
48} VC1ParseSearchState;
49
50typedef struct {
51    ParseContext pc;
52    VC1Context v;
53    uint8_t prev_start_code;
54    size_t bytes_to_skip;
55    uint8_t unesc_buffer[UNESCAPED_LIMIT];
56    size_t unesc_index;
57    VC1ParseSearchState search_state;
58} VC1ParseContext;
59
60static void vc1_extract_header(AVCodecParserContext *s, AVCodecContext *avctx,
61                               const uint8_t *buf, int buf_size)
62{
63    /* Parse the header we just finished unescaping */
64    VC1ParseContext *vpc = s->priv_data;
65    GetBitContext gb;
66    int ret;
67    vpc->v.s.avctx = avctx;
68    vpc->v.parse_only = 1;
69    init_get_bits(&gb, buf, buf_size * 8);
70    switch (vpc->prev_start_code) {
71    case VC1_CODE_SEQHDR & 0xFF:
72        ff_vc1_decode_sequence_header(avctx, &vpc->v, &gb);
73        break;
74    case VC1_CODE_ENTRYPOINT & 0xFF:
75        ff_vc1_decode_entry_point(avctx, &vpc->v, &gb);
76        break;
77    case VC1_CODE_FRAME & 0xFF:
78        if(vpc->v.profile < PROFILE_ADVANCED)
79            ret = ff_vc1_parse_frame_header    (&vpc->v, &gb);
80        else
81            ret = ff_vc1_parse_frame_header_adv(&vpc->v, &gb);
82
83        if (ret < 0)
84            break;
85
86        /* keep AV_PICTURE_TYPE_BI internal to VC1 */
87        if (vpc->v.s.pict_type == AV_PICTURE_TYPE_BI)
88            s->pict_type = AV_PICTURE_TYPE_B;
89        else
90            s->pict_type = vpc->v.s.pict_type;
91
92        if (avctx->ticks_per_frame > 1){
93            // process pulldown flags
94            s->repeat_pict = 1;
95            // Pulldown flags are only valid when 'broadcast' has been set.
96            // So ticks_per_frame will be 2
97            if (vpc->v.rff){
98                // repeat field
99                s->repeat_pict = 2;
100            }else if (vpc->v.rptfrm){
101                // repeat frames
102                s->repeat_pict = vpc->v.rptfrm * 2 + 1;
103            }
104        }else{
105            s->repeat_pict = 0;
106        }
107
108        if (vpc->v.broadcast && vpc->v.interlace && !vpc->v.psf)
109            s->field_order = vpc->v.tff ? AV_FIELD_TT : AV_FIELD_BB;
110        else
111            s->field_order = AV_FIELD_PROGRESSIVE;
112
113        break;
114    }
115}
116
117static int vc1_parse(AVCodecParserContext *s,
118                           AVCodecContext *avctx,
119                           const uint8_t **poutbuf, int *poutbuf_size,
120                           const uint8_t *buf, int buf_size)
121{
122    /* Here we do the searching for frame boundaries and headers at
123     * the same time. Only a minimal amount at the start of each
124     * header is unescaped. */
125    VC1ParseContext *vpc = s->priv_data;
126    int pic_found = vpc->pc.frame_start_found;
127    uint8_t *unesc_buffer = vpc->unesc_buffer;
128    size_t unesc_index = vpc->unesc_index;
129    VC1ParseSearchState search_state = vpc->search_state;
130    int next = END_NOT_FOUND;
131    int i = vpc->bytes_to_skip;
132
133    if (pic_found && buf_size == 0) {
134        /* EOF considered as end of frame */
135        memset(unesc_buffer + unesc_index, 0, UNESCAPED_THRESHOLD - unesc_index);
136        vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
137        next = 0;
138    }
139    while (i < buf_size) {
140        int start_code_found = 0;
141        uint8_t b;
142        while (i < buf_size && unesc_index < UNESCAPED_THRESHOLD) {
143            b = buf[i++];
144            unesc_buffer[unesc_index++] = b;
145            if (search_state <= ONE_ZERO)
146                search_state = b ? NO_MATCH : search_state + 1;
147            else if (search_state == TWO_ZEROS) {
148                if (b == 1)
149                    search_state = ONE;
150                else if (b > 1) {
151                    if (b == 3)
152                        unesc_index--; // swallow emulation prevention byte
153                    search_state = NO_MATCH;
154                }
155            }
156            else { // search_state == ONE
157                // Header unescaping terminates early due to detection of next start code
158                search_state = NO_MATCH;
159                start_code_found = 1;
160                break;
161            }
162        }
163        if ((s->flags & PARSER_FLAG_COMPLETE_FRAMES) &&
164                unesc_index >= UNESCAPED_THRESHOLD &&
165                vpc->prev_start_code == (VC1_CODE_FRAME & 0xFF))
166        {
167            // No need to keep scanning the rest of the buffer for
168            // start codes if we know it contains a complete frame and
169            // we've already unescaped all we need of the frame header
170            vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
171            break;
172        }
173        if (unesc_index >= UNESCAPED_THRESHOLD && !start_code_found) {
174            while (i < buf_size) {
175                if (search_state == NO_MATCH) {
176                    i += vpc->v.vc1dsp.vc1_find_start_code_candidate(buf + i, buf_size - i);
177                    if (i < buf_size) {
178                        search_state = ONE_ZERO;
179                    }
180                    i++;
181                } else {
182                    b = buf[i++];
183                    if (search_state == ONE_ZERO)
184                        search_state = b ? NO_MATCH : TWO_ZEROS;
185                    else if (search_state == TWO_ZEROS) {
186                        if (b >= 1)
187                            search_state = b == 1 ? ONE : NO_MATCH;
188                    }
189                    else { // search_state == ONE
190                        search_state = NO_MATCH;
191                        start_code_found = 1;
192                        break;
193                    }
194                }
195            }
196        }
197        if (start_code_found) {
198            vc1_extract_header(s, avctx, unesc_buffer, unesc_index);
199
200            vpc->prev_start_code = b;
201            unesc_index = 0;
202
203            if (!(s->flags & PARSER_FLAG_COMPLETE_FRAMES)) {
204                if (!pic_found && (b == (VC1_CODE_FRAME & 0xFF) || b == (VC1_CODE_FIELD & 0xFF))) {
205                    pic_found = 1;
206                }
207                else if (pic_found && b != (VC1_CODE_FIELD & 0xFF) && b != (VC1_CODE_SLICE & 0xFF)) {
208                    next = i - 4;
209                    pic_found = b == (VC1_CODE_FRAME & 0xFF);
210                    break;
211                }
212            }
213        }
214    }
215
216    vpc->pc.frame_start_found = pic_found;
217    vpc->unesc_index = unesc_index;
218    vpc->search_state = search_state;
219
220    if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
221        next = buf_size;
222    } else {
223        if (ff_combine_frame(&vpc->pc, next, &buf, &buf_size) < 0) {
224            vpc->bytes_to_skip = 0;
225            *poutbuf = NULL;
226            *poutbuf_size = 0;
227            return buf_size;
228        }
229    }
230
231    vpc->v.first_pic_header_flag = 1;
232
233    /* If we return with a valid pointer to a combined frame buffer
234     * then on the next call then we'll have been unhelpfully rewound
235     * by up to 4 bytes (depending upon whether the start code
236     * overlapped the input buffer, and if so by how much). We don't
237     * want this: it will either cause spurious second detections of
238     * the start code we've already seen, or cause extra bytes to be
239     * inserted at the start of the unescaped buffer. */
240    vpc->bytes_to_skip = 4;
241    if (next < 0 && next != END_NOT_FOUND)
242        vpc->bytes_to_skip += next;
243
244    *poutbuf = buf;
245    *poutbuf_size = buf_size;
246    return next;
247}
248
249static int vc1_split(AVCodecContext *avctx,
250                           const uint8_t *buf, int buf_size)
251{
252    int i;
253    uint32_t state= -1;
254    int charged=0;
255
256    for(i=0; i<buf_size; i++){
257        state= (state<<8) | buf[i];
258        if(IS_MARKER(state)){
259            if(state == VC1_CODE_SEQHDR || state == VC1_CODE_ENTRYPOINT){
260                charged=1;
261            }else if(charged){
262                return i-3;
263            }
264        }
265    }
266    return 0;
267}
268
269static av_cold int vc1_parse_init(AVCodecParserContext *s)
270{
271    VC1ParseContext *vpc = s->priv_data;
272    vpc->v.s.slice_context_count = 1;
273    vpc->v.first_pic_header_flag = 1;
274    vpc->prev_start_code = 0;
275    vpc->bytes_to_skip = 0;
276    vpc->unesc_index = 0;
277    vpc->search_state = NO_MATCH;
278    return ff_vc1_init_common(&vpc->v);
279}
280
281AVCodecParser ff_vc1_parser = {
282    .codec_ids      = { AV_CODEC_ID_VC1 },
283    .priv_data_size = sizeof(VC1ParseContext),
284    .parser_init    = vc1_parse_init,
285    .parser_parse   = vc1_parse,
286    .parser_close   = ff_parse_close,
287    .split          = vc1_split,
288};
289