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 "mpeg12.h"
25 #include "internal.h"
26 
27 struct MpvParseContext {
28     ParseContext pc;
29     AVRational frame_rate;
30     int progressive_sequence;
31     int width, height;
32 };
33 
34 
mpegvideo_extract_headers(AVCodecParserContext * s,AVCodecContext * avctx,const uint8_t * buf,int buf_size)35 static void mpegvideo_extract_headers(AVCodecParserContext *s,
36                                       AVCodecContext *avctx,
37                                       const uint8_t *buf, int buf_size)
38 {
39     struct MpvParseContext *pc = s->priv_data;
40     const uint8_t *buf_end = buf + buf_size;
41     uint32_t start_code;
42     int frame_rate_index, ext_type, bytes_left;
43     int frame_rate_ext_n, frame_rate_ext_d;
44     int top_field_first, repeat_first_field, progressive_frame;
45     int horiz_size_ext, vert_size_ext, bit_rate_ext;
46     int did_set_size=0;
47     int bit_rate = 0;
48     int vbv_delay = 0;
49 //FIXME replace the crap with get_bits()
50     s->repeat_pict = 0;
51 
52     while (buf < buf_end) {
53         start_code= -1;
54         buf= avpriv_find_start_code(buf, buf_end, &start_code);
55         bytes_left = buf_end - buf;
56         switch(start_code) {
57         case PICTURE_START_CODE:
58             if (bytes_left >= 2) {
59                 s->pict_type = (buf[1] >> 3) & 7;
60                 if (bytes_left >= 4)
61                 vbv_delay = ((buf[1] & 0x07) << 13) | (buf[2] << 5) | (buf[3]  >> 3);
62             }
63             break;
64         case SEQ_START_CODE:
65             if (bytes_left >= 7) {
66                 pc->width  = (buf[0] << 4) | (buf[1] >> 4);
67                 pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
68                 if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
69                     ff_set_dimensions(avctx, pc->width, pc->height);
70                     did_set_size=1;
71                 }
72                 frame_rate_index = buf[3] & 0xf;
73                 pc->frame_rate.den = avctx->time_base.den = ff_mpeg12_frame_rate_tab[frame_rate_index].num;
74                 pc->frame_rate.num = avctx->time_base.num = ff_mpeg12_frame_rate_tab[frame_rate_index].den;
75                 bit_rate = (buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6);
76                 avctx->codec_id = AV_CODEC_ID_MPEG1VIDEO;
77             }
78             break;
79         case EXT_START_CODE:
80             if (bytes_left >= 1) {
81                 ext_type = (buf[0] >> 4);
82                 switch(ext_type) {
83                 case 0x1: /* sequence extension */
84                     if (bytes_left >= 6) {
85                         horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
86                         vert_size_ext = (buf[2] >> 5) & 3;
87                         bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
88                         frame_rate_ext_n = (buf[5] >> 5) & 3;
89                         frame_rate_ext_d = (buf[5] & 0x1f);
90                         pc->progressive_sequence = buf[1] & (1 << 3);
91                         avctx->has_b_frames= !(buf[5] >> 7);
92 
93                         pc->width  |=(horiz_size_ext << 12);
94                         pc->height |=( vert_size_ext << 12);
95                         bit_rate = (bit_rate&0x3FFFF) | (bit_rate_ext << 18);
96                         if(did_set_size)
97                             ff_set_dimensions(avctx, pc->width, pc->height);
98                         avctx->time_base.den = pc->frame_rate.den * (frame_rate_ext_n + 1) * 2;
99                         avctx->time_base.num = pc->frame_rate.num * (frame_rate_ext_d + 1);
100                         avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;
101                     }
102                     break;
103                 case 0x8: /* picture coding extension */
104                     if (bytes_left >= 5) {
105                         top_field_first = buf[3] & (1 << 7);
106                         repeat_first_field = buf[3] & (1 << 1);
107                         progressive_frame = buf[4] & (1 << 7);
108 
109                         /* check if we must repeat the frame */
110                         s->repeat_pict = 1;
111                         if (repeat_first_field) {
112                             if (pc->progressive_sequence) {
113                                 if (top_field_first)
114                                     s->repeat_pict = 5;
115                                 else
116                                     s->repeat_pict = 3;
117                             } else if (progressive_frame) {
118                                 s->repeat_pict = 2;
119                             }
120                         }
121 
122                         if (!pc->progressive_sequence) {
123                             if (top_field_first)
124                                 s->field_order = AV_FIELD_TT;
125                             else
126                                 s->field_order = AV_FIELD_BB;
127                         } else
128                             s->field_order = AV_FIELD_PROGRESSIVE;
129                     }
130                     break;
131                 }
132             }
133             break;
134         case -1:
135             goto the_end;
136         default:
137             /* we stop parsing when we encounter a slice. It ensures
138                that this function takes a negligible amount of time */
139             if (start_code >= SLICE_MIN_START_CODE &&
140                 start_code <= SLICE_MAX_START_CODE)
141                 goto the_end;
142             break;
143         }
144     }
145  the_end: ;
146     if (avctx->codec_id == AV_CODEC_ID_MPEG2VIDEO && bit_rate) {
147         avctx->rc_max_rate = 400*bit_rate;
148     }
149     if (bit_rate &&
150         ((avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO && bit_rate != 0x3FFFF) || vbv_delay != 0xFFFF)) {
151         avctx->bit_rate = 400*bit_rate;
152     }
153 }
154 
mpegvideo_parse(AVCodecParserContext * s,AVCodecContext * avctx,const uint8_t ** poutbuf,int * poutbuf_size,const uint8_t * buf,int buf_size)155 static int mpegvideo_parse(AVCodecParserContext *s,
156                            AVCodecContext *avctx,
157                            const uint8_t **poutbuf, int *poutbuf_size,
158                            const uint8_t *buf, int buf_size)
159 {
160     struct MpvParseContext *pc1 = s->priv_data;
161     ParseContext *pc= &pc1->pc;
162     int next;
163 
164     if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
165         next= buf_size;
166     }else{
167         next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
168 
169         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
170             *poutbuf = NULL;
171             *poutbuf_size = 0;
172             return buf_size;
173         }
174 
175     }
176     /* we have a full frame : we just parse the first few MPEG headers
177        to have the full timing information. The time take by this
178        function should be negligible for uncorrupted streams */
179     mpegvideo_extract_headers(s, avctx, buf, buf_size);
180     av_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
181             s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
182 
183     *poutbuf = buf;
184     *poutbuf_size = buf_size;
185     return next;
186 }
187 
mpegvideo_split(AVCodecContext * avctx,const uint8_t * buf,int buf_size)188 static int mpegvideo_split(AVCodecContext *avctx,
189                            const uint8_t *buf, int buf_size)
190 {
191     int i;
192     uint32_t state= -1;
193     int found=0;
194 
195     for(i=0; i<buf_size; i++){
196         state= (state<<8) | buf[i];
197         if(state == 0x1B3){
198             found=1;
199         }else if(found && state != 0x1B5 && state < 0x200 && state >= 0x100)
200             return i-3;
201     }
202     return 0;
203 }
204 
mpegvideo_parse_init(AVCodecParserContext * s)205 static int mpegvideo_parse_init(AVCodecParserContext *s)
206 {
207     s->pict_type = AV_PICTURE_TYPE_NONE; // first frame might be partial
208     return 0;
209 }
210 
211 AVCodecParser ff_mpegvideo_parser = {
212 	.codec_ids      = { AV_CODEC_ID_MPEG1VIDEO, AV_CODEC_ID_MPEG2VIDEO },
213     .priv_data_size = sizeof(struct MpvParseContext),
214     .parser_init    = mpegvideo_parse_init,
215     .parser_parse   = mpegvideo_parse,
216     .parser_close   = ff_parse_close,
217     .split          = mpegvideo_split,
218 };
219