1/*
2 * MPEG1 / MPEG2 video parser
3 * Copyright (c) 2000,2001 Fabrice Bellard
4 * Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
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#include "parser.h"
24#include "mpegvideo.h"
25
26static void mpegvideo_extract_headers(AVCodecParserContext *s,
27                                      AVCodecContext *avctx,
28                                      const uint8_t *buf, int buf_size)
29{
30    ParseContext1 *pc = s->priv_data;
31    const uint8_t *buf_end;
32    const uint8_t *buf_start= buf;
33    uint32_t start_code;
34    int frame_rate_index, ext_type, bytes_left;
35    int frame_rate_ext_n, frame_rate_ext_d;
36    int picture_structure, top_field_first, repeat_first_field, progressive_frame;
37    int horiz_size_ext, vert_size_ext, bit_rate_ext;
38//FIXME replace the crap with get_bits()
39    s->repeat_pict = 0;
40    buf_end = buf + buf_size;
41    while (buf < buf_end) {
42        start_code= -1;
43        buf= ff_find_start_code(buf, buf_end, &start_code);
44        bytes_left = buf_end - buf;
45        switch(start_code) {
46        case PICTURE_START_CODE:
47            ff_fetch_timestamp(s, buf-buf_start-4, 1);
48
49            if (bytes_left >= 2) {
50                s->pict_type = (buf[1] >> 3) & 7;
51            }
52            break;
53        case SEQ_START_CODE:
54            if (bytes_left >= 7) {
55                pc->width  = (buf[0] << 4) | (buf[1] >> 4);
56                pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
57                avcodec_set_dimensions(avctx, pc->width, pc->height);
58                frame_rate_index = buf[3] & 0xf;
59                pc->frame_rate.den = avctx->time_base.den = ff_frame_rate_tab[frame_rate_index].num;
60                pc->frame_rate.num = avctx->time_base.num = ff_frame_rate_tab[frame_rate_index].den;
61                avctx->bit_rate = ((buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6))*400;
62                avctx->codec_id = CODEC_ID_MPEG1VIDEO;
63                avctx->sub_id = 1;
64            }
65            break;
66        case EXT_START_CODE:
67            if (bytes_left >= 1) {
68                ext_type = (buf[0] >> 4);
69                switch(ext_type) {
70                case 0x1: /* sequence extension */
71                    if (bytes_left >= 6) {
72                        horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
73                        vert_size_ext = (buf[2] >> 5) & 3;
74                        bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
75                        frame_rate_ext_n = (buf[5] >> 5) & 3;
76                        frame_rate_ext_d = (buf[5] & 0x1f);
77                        pc->progressive_sequence = buf[1] & (1 << 3);
78                        avctx->has_b_frames= !(buf[5] >> 7);
79
80                        pc->width  |=(horiz_size_ext << 12);
81                        pc->height |=( vert_size_ext << 12);
82                        avctx->bit_rate += (bit_rate_ext << 18) * 400;
83                        avcodec_set_dimensions(avctx, pc->width, pc->height);
84                        avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1) * 2;
85                        avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
86                        avctx->codec_id = CODEC_ID_MPEG2VIDEO;
87                        avctx->sub_id = 2; /* forces MPEG2 */
88                    }
89                    break;
90                case 0x8: /* picture coding extension */
91                    if (bytes_left >= 5) {
92                        picture_structure = buf[2]&3;
93                        top_field_first = buf[3] & (1 << 7);
94                        repeat_first_field = buf[3] & (1 << 1);
95                        progressive_frame = buf[4] & (1 << 7);
96
97                        /* check if we must repeat the frame */
98                        s->repeat_pict = 1;
99                        if (repeat_first_field) {
100                            if (pc->progressive_sequence) {
101                                if (top_field_first)
102                                    s->repeat_pict = 5;
103                                else
104                                    s->repeat_pict = 3;
105                            } else if (progressive_frame) {
106                                s->repeat_pict = 2;
107                            }
108                        }
109                    }
110                    break;
111                }
112            }
113            break;
114        case -1:
115            goto the_end;
116        default:
117            /* we stop parsing when we encounter a slice. It ensures
118               that this function takes a negligible amount of time */
119            if (start_code >= SLICE_MIN_START_CODE &&
120                start_code <= SLICE_MAX_START_CODE)
121                goto the_end;
122            break;
123        }
124    }
125 the_end: ;
126}
127
128static int mpegvideo_parse(AVCodecParserContext *s,
129                           AVCodecContext *avctx,
130                           const uint8_t **poutbuf, int *poutbuf_size,
131                           const uint8_t *buf, int buf_size)
132{
133    ParseContext1 *pc1 = s->priv_data;
134    ParseContext *pc= &pc1->pc;
135    int next;
136
137    if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
138        next= buf_size;
139    }else{
140        next= ff_mpeg1_find_frame_end(pc, buf, buf_size);
141
142        if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
143            *poutbuf = NULL;
144            *poutbuf_size = 0;
145            return buf_size;
146        }
147
148    }
149    /* we have a full frame : we just parse the first few MPEG headers
150       to have the full timing information. The time take by this
151       function should be negligible for uncorrupted streams */
152    mpegvideo_extract_headers(s, avctx, buf, buf_size);
153#if 0
154    printf("pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
155           s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
156#endif
157
158    *poutbuf = buf;
159    *poutbuf_size = buf_size;
160    return next;
161}
162
163static int mpegvideo_split(AVCodecContext *avctx,
164                           const uint8_t *buf, int buf_size)
165{
166    int i;
167    uint32_t state= -1;
168
169    for(i=0; i<buf_size; i++){
170        state= (state<<8) | buf[i];
171        if(state != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100)
172            return i-3;
173    }
174    return 0;
175}
176
177AVCodecParser mpegvideo_parser = {
178    { CODEC_ID_MPEG1VIDEO, CODEC_ID_MPEG2VIDEO },
179    sizeof(ParseContext1),
180    NULL,
181    mpegvideo_parse,
182    ff_parse1_close,
183};
184