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 Libav.
7 *
8 * Libav 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 * Libav 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 Libav; 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 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= avpriv_mpv_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 = avpriv_frame_rate_tab[frame_rate_index].num;
61                pc->frame_rate.num = avctx->time_base.num = avpriv_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                        top_field_first = buf[3] & (1 << 7);
95                        repeat_first_field = buf[3] & (1 << 1);
96                        progressive_frame = buf[4] & (1 << 7);
97
98                        /* check if we must repeat the frame */
99                        s->repeat_pict = 1;
100                        if (repeat_first_field) {
101                            if (pc->progressive_sequence) {
102                                if (top_field_first)
103                                    s->repeat_pict = 5;
104                                else
105                                    s->repeat_pict = 3;
106                            } else if (progressive_frame) {
107                                s->repeat_pict = 2;
108                            }
109                        }
110                    }
111                    break;
112                }
113            }
114            break;
115        case -1:
116            goto the_end;
117        default:
118            /* we stop parsing when we encounter a slice. It ensures
119               that this function takes a negligible amount of time */
120            if (start_code >= SLICE_MIN_START_CODE &&
121                start_code <= SLICE_MAX_START_CODE)
122                goto the_end;
123            break;
124        }
125    }
126 the_end: ;
127}
128
129static int mpegvideo_parse(AVCodecParserContext *s,
130                           AVCodecContext *avctx,
131                           const uint8_t **poutbuf, int *poutbuf_size,
132                           const uint8_t *buf, int buf_size)
133{
134    ParseContext1 *pc1 = s->priv_data;
135    ParseContext *pc= &pc1->pc;
136    int next;
137
138    if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
139        next= buf_size;
140    }else{
141        next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
142
143        if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
144            *poutbuf = NULL;
145            *poutbuf_size = 0;
146            return buf_size;
147        }
148
149    }
150    /* we have a full frame : we just parse the first few MPEG headers
151       to have the full timing information. The time take by this
152       function should be negligible for uncorrupted streams */
153    mpegvideo_extract_headers(s, avctx, buf, buf_size);
154    av_dlog(NULL, "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
157    *poutbuf = buf;
158    *poutbuf_size = buf_size;
159    return next;
160}
161
162static int mpegvideo_split(AVCodecContext *avctx,
163                           const uint8_t *buf, int buf_size)
164{
165    int i;
166    uint32_t state= -1;
167
168    for(i=0; i<buf_size; i++){
169        state= (state<<8) | buf[i];
170        if(state != 0x1B3 && state != 0x1B5 && state < 0x200 && state >= 0x100)
171            return i-3;
172    }
173    return 0;
174}
175
176AVCodecParser ff_mpegvideo_parser = {
177    .codec_ids      = { CODEC_ID_MPEG1VIDEO, CODEC_ID_MPEG2VIDEO },
178    .priv_data_size = sizeof(ParseContext1),
179    .parser_parse   = mpegvideo_parse,
180    .parser_close   = ff_parse1_close,
181    .split          = mpegvideo_split,
182};
183