summaryrefslogtreecommitdiffstats
path: root/libavcodec/mpegvideo_parser.c
blob: 30f149d5476d683daed4bc64c44282c7e76c7665 (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
/*
 * MPEG1 / MPEG2 video parser
 * Copyright (c) 2000,2001 Fabrice Bellard.
 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
 *
 * 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
 */

#include "parser.h"
#include "mpegvideo.h"

static void mpegvideo_extract_headers(AVCodecParserContext *s,
                                      AVCodecContext *avctx,
                                      const uint8_t *buf, int buf_size)
{
    ParseContext1 *pc = s->priv_data;
    const uint8_t *buf_end;
    const uint8_t *buf_start= buf;
    uint32_t start_code;
    int frame_rate_index, ext_type, bytes_left;
    int frame_rate_ext_n, frame_rate_ext_d;
    int picture_structure, top_field_first, repeat_first_field, progressive_frame;
    int horiz_size_ext, vert_size_ext, bit_rate_ext;
//FIXME replace the crap with get_bits()
    s->repeat_pict = 0;
    buf_end = buf + buf_size;
    while (buf < buf_end) {
        start_code= -1;
        buf= ff_find_start_code(buf, buf_end, &start_code);
        bytes_left = buf_end - buf;
        switch(start_code) {
        case PICTURE_START_CODE:
            ff_fetch_timestamp(s, buf-buf_start-4, 1);

            if (bytes_left >= 2) {
                s->pict_type = (buf[1] >> 3) & 7;
            }
            break;
        case SEQ_START_CODE:
            if (bytes_left >= 7) {
                pc->width  = (buf[0] << 4) | (buf[1] >> 4);
                pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
                avcodec_set_dimensions(avctx, pc->width, pc->height);
                frame_rate_index = buf[3] & 0xf;
                pc->frame_rate.den = avctx->time_base.den = ff_frame_rate_tab[frame_rate_index].num;
                pc->frame_rate.num = avctx->time_base.num = ff_frame_rate_tab[frame_rate_index].den;
                avctx->bit_rate = ((buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6))*400;
                avctx->codec_id = CODEC_ID_MPEG1VIDEO;
                avctx->sub_id = 1;
            }
            break;
        case EXT_START_CODE:
            if (bytes_left >= 1) {
                ext_type = (buf[0] >> 4);
                switch(ext_type) {
                case 0x1: /* sequence extension */
                    if (bytes_left >= 6) {
                        horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
                        vert_size_ext = (buf[2] >> 5) & 3;
                        bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
                        frame_rate_ext_n = (buf[5] >> 5) & 3;
                        frame_rate_ext_d = (buf[5] & 0x1f);
                        pc->progressive_sequence = buf[1] & (1 << 3);
                        avctx->has_b_frames= !(buf[5] >> 7);

                        pc->width  |=(horiz_size_ext << 12);
                        pc->height |=( vert_size_ext << 12);
                        avctx->bit_rate += (bit_rate_ext << 18) * 400;
                        avcodec_set_dimensions(avctx, pc->width, pc->height);
                        avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1);
                        avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
                        avctx->codec_id = CODEC_ID_MPEG2VIDEO;
                        avctx->sub_id = 2; /* forces MPEG2 */
                    }
                    break;
                case 0x8: /* picture coding extension */
                    if (bytes_left >= 5) {
                        picture_structure = buf[2]&3;
                        top_field_first = buf[3] & (1 << 7);
                        repeat_first_field = buf[3] & (1 << 1);
                        progressive_frame = buf[4] & (1 << 7);

                        /* check if we must repeat the frame */
                        if (repeat_first_field) {
                            if (pc->progressive_sequence) {
                                if (top_field_first)
                                    s->repeat_pict = 4;
                                else
                                    s->repeat_pict = 2;
                            } else if (progressive_frame) {
                                s->repeat_pict = 1;
                            }
                        }
                    }
                    break;
                }
            }
            break;
        case -1:
            goto the_end;
        default:
            /* we stop parsing when we encounter a slice. It ensures
               that this function takes a negligible amount of time */
            if (start_code >= SLICE_MIN_START_CODE &&
                start_code <= SLICE_MAX_START_CODE)
                goto the_end;
            break;
        }
    }
 the_end: ;
}

static int mpegvideo_parse(AVCodecParserContext *s,
                           AVCodecContext *avctx,
                           const uint8_t **poutbuf, int *poutbuf_size,
                           const uint8_t *buf, int buf_size)
{
    ParseContext1 *pc1 = s->priv_data;
    ParseContext *pc= &pc1->pc;
    int next;

    if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
        next= buf_size;
    }else{
        next= ff_mpeg1_find_frame_end(pc, buf, buf_size);

        if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
            *poutbuf = NULL;
            *poutbuf_size = 0;
            return buf_size;
        }

    }
    /* we have a full frame : we just parse the first few MPEG headers
       to have the full timing information. The time take by this
       function should be negligible for uncorrupted streams */
    mpegvideo_extract_headers(s, avctx, buf, buf_size);
#if 0
    printf("pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
           s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
#endif

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

static int mpegvideo_split(AVCodecContext *avctx,
                           const uint8_t *buf, int buf_size)
{
    int i;
    uint32_t state= -1;

    for(i=0; i<buf_size; i++){
        state= (state<<8) | buf[i];
        if(state != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100)
            return i-3;
    }
    return 0;
}

AVCodecParser mpegvideo_parser = {
    { CODEC_ID_MPEG1VIDEO, CODEC_ID_MPEG2VIDEO },
    sizeof(ParseContext1),
    NULL,
    mpegvideo_parse,
    ff_parse1_close,
};
OpenPOWER on IntegriCloud