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 = buf + buf_size;
32    uint32_t start_code;
33    int frame_rate_index, ext_type, bytes_left;
34    int frame_rate_ext_n, frame_rate_ext_d;
35    int picture_structure, top_field_first, repeat_first_field, progressive_frame;
36    int horiz_size_ext, vert_size_ext, bit_rate_ext;
37    int did_set_size=0;
38//FIXME replace the crap with get_bits()
39    s->repeat_pict = 0;
40
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            if (bytes_left >= 2) {
48                s->pict_type = (buf[1] >> 3) & 7;
49            }
50            break;
51        case SEQ_START_CODE:
52            if (bytes_left >= 7) {
53                pc->width  = (buf[0] << 4) | (buf[1] >> 4);
54                pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
55                if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
56                    avcodec_set_dimensions(avctx, pc->width, pc->height);
57                    did_set_size=1;
58                }
59                frame_rate_index = buf[3] & 0xf;
60                pc->frame_rate.den = avctx->time_base.den = ff_frame_rate_tab[frame_rate_index].num;
61                pc->frame_rate.num = avctx->time_base.num = ff_frame_rate_tab[frame_rate_index].den;
62                avctx->bit_rate = ((buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6))*400;
63                avctx->codec_id = CODEC_ID_MPEG1VIDEO;
64                avctx->sub_id = 1;
65            }
66            break;
67        case EXT_START_CODE:
68            if (bytes_left >= 1) {
69                ext_type = (buf[0] >> 4);
70                switch(ext_type) {
71                case 0x1: /* sequence extension */
72                    if (bytes_left >= 6) {
73                        horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
74                        vert_size_ext = (buf[2] >> 5) & 3;
75                        bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
76                        frame_rate_ext_n = (buf[5] >> 5) & 3;
77                        frame_rate_ext_d = (buf[5] & 0x1f);
78                        pc->progressive_sequence = buf[1] & (1 << 3);
79                        avctx->has_b_frames= !(buf[5] >> 7);
80
81                        pc->width  |=(horiz_size_ext << 12);
82                        pc->height |=( vert_size_ext << 12);
83                        avctx->bit_rate += (bit_rate_ext << 18) * 400;
84                        if(did_set_size)
85                            avcodec_set_dimensions(avctx, pc->width, pc->height);
86                        avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1) * 2;
87                        avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
88                        avctx->codec_id = CODEC_ID_MPEG2VIDEO;
89                        avctx->sub_id = 2; /* forces MPEG2 */
90                    }
91                    break;
92                case 0x8: /* picture coding extension */
93                    if (bytes_left >= 5) {
94                        picture_structure = buf[2]&3;
95                        top_field_first = buf[3] & (1 << 7);
96                        repeat_first_field = buf[3] & (1 << 1);
97                        progressive_frame = buf[4] & (1 << 7);
98
99                        /* check if we must repeat the frame */
100                        s->repeat_pict = 1;
101                        if (repeat_first_field) {
102                            if (pc->progressive_sequence) {
103                                if (top_field_first)
104                                    s->repeat_pict = 5;
105                                else
106                                    s->repeat_pict = 3;
107                            } else if (progressive_frame) {
108                                s->repeat_pict = 2;
109                            }
110                        }
111                    }
112                    break;
113                }
114            }
115            break;
116        case -1:
117            goto the_end;
118        default:
119            /* we stop parsing when we encounter a slice. It ensures
120               that this function takes a negligible amount of time */
121            if (start_code >= SLICE_MIN_START_CODE &&
122                start_code <= SLICE_MAX_START_CODE)
123                goto the_end;
124            break;
125        }
126    }
127 the_end: ;
128}
129
130static int mpegvideo_parse(AVCodecParserContext *s,
131                           AVCodecContext *avctx,
132                           const uint8_t **poutbuf, int *poutbuf_size,
133                           const uint8_t *buf, int buf_size)
134{
135    ParseContext1 *pc1 = s->priv_data;
136    ParseContext *pc= &pc1->pc;
137    int next;
138
139    if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
140        next= buf_size;
141    }else{
142        next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
143
144        if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
145            *poutbuf = NULL;
146            *poutbuf_size = 0;
147            return buf_size;
148        }
149
150    }
151    /* we have a full frame : we just parse the first few MPEG headers
152       to have the full timing information. The time take by this
153       function should be negligible for uncorrupted streams */
154    mpegvideo_extract_headers(s, avctx, buf, buf_size);
155#if 0
156    printf("pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
157           s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
158#endif
159
160    *poutbuf = buf;
161    *poutbuf_size = buf_size;
162    return next;
163}
164
165static int mpegvideo_split(AVCodecContext *avctx,
166                           const uint8_t *buf, int buf_size)
167{
168    int i;
169    uint32_t state= -1;
170
171    for(i=0; i<buf_size; i++){
172        state= (state<<8) | buf[i];
173        if(state != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100)
174            return i-3;
175    }
176    return 0;
177}
178
179AVCodecParser mpegvideo_parser = {
180    { CODEC_ID_MPEG1VIDEO, CODEC_ID_MPEG2VIDEO },
181    sizeof(ParseContext1),
182    NULL,
183    mpegvideo_parse,
184    ff_parse1_close,
185    mpegvideo_split,
186};
187