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path: root/libavcodec/mpegvideo_parser.c (plain)
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1/*
2 * MPEG-1 / MPEG-2 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
27struct MpvParseContext {
28 ParseContext pc;
29 AVRational frame_rate;
30 int progressive_sequence;
31 int width, height;
32};
33
34
35static 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 set_dim_ret = 0;
48 int bit_rate = 0;
49 int vbv_delay = 0;
50 int chroma_format;
51 enum AVPixelFormat pix_fmt = AV_PIX_FMT_NONE;
52//FIXME replace the crap with get_bits()
53 s->repeat_pict = 0;
54
55 while (buf < buf_end) {
56 start_code= -1;
57 buf= avpriv_find_start_code(buf, buf_end, &start_code);
58 bytes_left = buf_end - buf;
59 switch(start_code) {
60 case PICTURE_START_CODE:
61 if (bytes_left >= 2) {
62 s->pict_type = (buf[1] >> 3) & 7;
63 if (bytes_left >= 4)
64 vbv_delay = ((buf[1] & 0x07) << 13) | (buf[2] << 5) | (buf[3] >> 3);
65 }
66 break;
67 case SEQ_START_CODE:
68 if (bytes_left >= 7) {
69 pc->width = (buf[0] << 4) | (buf[1] >> 4);
70 pc->height = ((buf[1] & 0x0f) << 8) | buf[2];
71 if(!avctx->width || !avctx->height || !avctx->coded_width || !avctx->coded_height){
72 set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
73 did_set_size=1;
74 }
75 pix_fmt = AV_PIX_FMT_YUV420P;
76 frame_rate_index = buf[3] & 0xf;
77 pc->frame_rate = avctx->framerate = ff_mpeg12_frame_rate_tab[frame_rate_index];
78 bit_rate = (buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6);
79 avctx->codec_id = AV_CODEC_ID_MPEG1VIDEO;
80 avctx->ticks_per_frame = 1;
81 }
82 break;
83 case EXT_START_CODE:
84 if (bytes_left >= 1) {
85 ext_type = (buf[0] >> 4);
86 switch(ext_type) {
87 case 0x1: /* sequence extension */
88 if (bytes_left >= 6) {
89 horiz_size_ext = ((buf[1] & 1) << 1) | (buf[2] >> 7);
90 vert_size_ext = (buf[2] >> 5) & 3;
91 bit_rate_ext = ((buf[2] & 0x1F)<<7) | (buf[3]>>1);
92 frame_rate_ext_n = (buf[5] >> 5) & 3;
93 frame_rate_ext_d = (buf[5] & 0x1f);
94 pc->progressive_sequence = buf[1] & (1 << 3);
95 avctx->has_b_frames= !(buf[5] >> 7);
96
97 chroma_format = (buf[1] >> 1) & 3;
98 switch (chroma_format) {
99 case 1: pix_fmt = AV_PIX_FMT_YUV420P; break;
100 case 2: pix_fmt = AV_PIX_FMT_YUV422P; break;
101 case 3: pix_fmt = AV_PIX_FMT_YUV444P; break;
102 }
103
104 pc->width = (pc->width & 0xFFF) | (horiz_size_ext << 12);
105 pc->height = (pc->height& 0xFFF) | ( vert_size_ext << 12);
106 bit_rate = (bit_rate&0x3FFFF) | (bit_rate_ext << 18);
107 if(did_set_size)
108 set_dim_ret = ff_set_dimensions(avctx, pc->width, pc->height);
109 avctx->framerate.num = pc->frame_rate.num * (frame_rate_ext_n + 1);
110 avctx->framerate.den = pc->frame_rate.den * (frame_rate_ext_d + 1);
111 avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;
112 avctx->ticks_per_frame = 2;
113 }
114 break;
115 case 0x8: /* picture coding extension */
116 if (bytes_left >= 5) {
117 top_field_first = buf[3] & (1 << 7);
118 repeat_first_field = buf[3] & (1 << 1);
119 progressive_frame = buf[4] & (1 << 7);
120
121 /* check if we must repeat the frame */
122 s->repeat_pict = 1;
123 if (repeat_first_field) {
124 if (pc->progressive_sequence) {
125 if (top_field_first)
126 s->repeat_pict = 5;
127 else
128 s->repeat_pict = 3;
129 } else if (progressive_frame) {
130 s->repeat_pict = 2;
131 }
132 }
133
134 if (!pc->progressive_sequence) {
135 if (top_field_first)
136 s->field_order = AV_FIELD_TT;
137 else
138 s->field_order = AV_FIELD_BB;
139 } else
140 s->field_order = AV_FIELD_PROGRESSIVE;
141 }
142 break;
143 }
144 }
145 break;
146 case -1:
147 goto the_end;
148 default:
149 /* we stop parsing when we encounter a slice. It ensures
150 that this function takes a negligible amount of time */
151 if (start_code >= SLICE_MIN_START_CODE &&
152 start_code <= SLICE_MAX_START_CODE)
153 goto the_end;
154 break;
155 }
156 }
157 the_end: ;
158 if (set_dim_ret < 0)
159 av_log(avctx, AV_LOG_ERROR, "Failed to set dimensions\n");
160
161 if (avctx->codec_id == AV_CODEC_ID_MPEG2VIDEO && bit_rate) {
162 avctx->rc_max_rate = 400LL*bit_rate;
163 }
164 if (bit_rate &&
165 ((avctx->codec_id == AV_CODEC_ID_MPEG1VIDEO && bit_rate != 0x3FFFF) || vbv_delay != 0xFFFF)) {
166 avctx->bit_rate = 400LL*bit_rate;
167 }
168
169 if (pix_fmt != AV_PIX_FMT_NONE) {
170 s->format = pix_fmt;
171 s->width = pc->width;
172 s->height = pc->height;
173 s->coded_width = FFALIGN(pc->width, 16);
174 s->coded_height = FFALIGN(pc->height, 16);
175 }
176
177#if FF_API_AVCTX_TIMEBASE
178 if (avctx->framerate.num)
179 avctx->time_base = av_inv_q(av_mul_q(avctx->framerate, (AVRational){avctx->ticks_per_frame, 1}));
180#endif
181}
182
183static int mpegvideo_parse(AVCodecParserContext *s,
184 AVCodecContext *avctx,
185 const uint8_t **poutbuf, int *poutbuf_size,
186 const uint8_t *buf, int buf_size)
187{
188 struct MpvParseContext *pc1 = s->priv_data;
189 ParseContext *pc= &pc1->pc;
190 int next;
191
192 if(s->flags & PARSER_FLAG_COMPLETE_FRAMES){
193 next= buf_size;
194 }else{
195 next= ff_mpeg1_find_frame_end(pc, buf, buf_size, s);
196
197 if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
198 *poutbuf = NULL;
199 *poutbuf_size = 0;
200 return buf_size;
201 }
202
203 }
204 /* we have a full frame : we just parse the first few MPEG headers
205 to have the full timing information. The time take by this
206 function should be negligible for uncorrupted streams */
207 mpegvideo_extract_headers(s, avctx, buf, buf_size);
208 ff_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
209 s->pict_type, av_q2d(avctx->framerate), s->repeat_pict);
210
211 *poutbuf = buf;
212 *poutbuf_size = buf_size;
213 return next;
214}
215
216static int mpegvideo_split(AVCodecContext *avctx,
217 const uint8_t *buf, int buf_size)
218{
219 int i;
220 uint32_t state= -1;
221 int found=0;
222
223 for(i=0; i<buf_size; i++){
224 state= (state<<8) | buf[i];
225 if(state == 0x1B3){
226 found=1;
227 }else if(found && state != 0x1B5 && state < 0x200 && state >= 0x100)
228 return i-3;
229 }
230 return 0;
231}
232
233static int mpegvideo_parse_init(AVCodecParserContext *s)
234{
235 s->pict_type = AV_PICTURE_TYPE_NONE; // first frame might be partial
236 return 0;
237}
238
239AVCodecParser ff_mpegvideo_parser = {
240 .codec_ids = { AV_CODEC_ID_MPEG1VIDEO, AV_CODEC_ID_MPEG2VIDEO },
241 .priv_data_size = sizeof(struct MpvParseContext),
242 .parser_init = mpegvideo_parse_init,
243 .parser_parse = mpegvideo_parse,
244 .parser_close = ff_parse_close,
245 .split = mpegvideo_split,
246};
247
generated by cgit at 2024-05-17 18:55:07 (GMT)